Research of the high performance low temperature vortex street flowmeter

NASA Astrophysics Data System (ADS)

Gao, Feng; Chen, Yang; Zhang, Zhen-peng; Geng, Wei-guo

2007-07-01

Flow measurement is the key method for R&D and operation monitoring of liquid rocket engine. Therefore, it is important to measure flux of low temperature liquid propellants for the liquid hydrogen/liquid oxygen or the liquid oxygen/kerosene rocket engine. Presently in China, the level meter and the turbine flowmeter are usually used in the experimentation of the liquid hydrogen/liquid oxygen rocket engine. The level meter can only scale average flux and the precision of the turbine flowmeter (the measuring wild point is 1.5%) can not be ensured due to the reason which there is not devices of low temperature real-time demarcation in China. Therefore, it is required to research the high performance low temperature flow measurement equipment and the vortex street flowmeter is selected because of its advantages. In the paper, some key techniques of low temperature vortex street flowmeter are researched from the design aspect. Firstly, the basic theoretical research of vortex street flowmeter includes signal detection method, shape of vortex producer and effects of dimension of vertex producer to vortex quality. Secondly, low temperature vortex street flowmeter adopts the method of piezoelectric components stress mode. As for the weakness of phase-change, lattice change and fragility for many piezoelectric materials in low temperature, it can not be fulfilled piezoelectric signal and mechanism performance under this condition. Some piezoelectric materials which can be used in low temperature are illustrated in the paper by lots of research in order for the farther research. The article places emphasis upon low temperature trait of piezoelectric materials, and the structure designs of signal detector and calculation of stress, electric charge quantity and heat transfer.

Quantum oscillations in vortex-liquids

NASA Astrophysics Data System (ADS)

Banerjee, Sumilan; Zhang, Shizhong; Randeria, Mohit

2012-02-01

Motivated by observations of quantum oscillations in underdoped cuprates [1], we examine the electronic density of states (DOS) in a vortex-liquid state, where long-range phase coherence is destroyed by an external magnetic field H but the local pairing amplitude survives. We note that this regime is distinct from that studied in most of the recent theories, which have focused on either a Fermi liquid with a competing order parameter or on a d-wave vortex lattice. The cuprate experiments are very likely in a resistive vortex-liquid state. We generalize the s-wave analysis of Maki and Stephen [2] to d-wave pairing and examine various regimes of the chemical potential, gap and field. We find that the (1/H) oscillations of the DOS at the chemical potential in a d-wave vortex-liquid are much more robust, i.e., have a reduced damping, compared to the s-wave case. We critically investigate the conventional wisdom relating the observed frequency to the area of an underlying Fermi surface. We also show that the oscillations in the DOS cross over to a √H behavior in the low field limit, in agreement with the recent specific heat measurements. [1] L. Taillefer, J. Phys. Cond. Mat. 21, 164212 (2009). [2] M. J. Stephen, Phys. Rev. B 45, 5481 (1992).

Magnetic phase diagram of underdoped YBa 2 Cu 3 O y inferred from torque magnetization and thermal conductivity

DOE PAGES

Yu, Fan; Hirschberger, Max; Loew, Toshinao; ...

2016-10-24

We obtain the magnetic phase diagram in the underdoped cuprate YBa2Cu3Oy using torque magnetometry at temperatures 0.3–70 K and magnetic fields up to 45 T. At low fields, vortices (quantized flux tubes) form a vortex solid that is strongly pinned to the lattice. At large fields, melting of the solid to a vortex liquid produces nonzero dissipation. However, the vortex liquid persists to fields above 41 T. We have also mapped out the “transition” fields at which the charge-density–wave state (observed in X-ray diffraction experiments) becomes stable. Our results show that, in intense fields, superconductivity adjusts to coexist with themore » charge-density wave, but the Cooper pairs, which define the superconducting fluid, survive to fields well above 41 T.« less

Simultaneous extraction and quantification of albendazole and triclabendazole using vortex-assisted hollow-fiber liquid-phase microextraction combined with high-performance liquid chromatography.

PubMed

Asadi, Mohammad; Haji Shabani, Ali Mohammad; Dadfarnia, Shayessteh

2016-06-01

A novel, simple, and rapid vortex-assisted hollow-fiber liquid-phase microextraction method was developed for the simultaneous extraction of albendazole and triclabendazole from various matrices before their determination by high-performance liquid chromatography with fluorescence detection. Several factors influencing the microextraction efficiency including sample pH, nature and volume of extraction solvent, ionic strength, vortex time, and sample volume were investigated and optimized. Under the optimal conditions, the limits of detection were 0.08 and 0.12 μg/L for albendazole and triclabendazole, respectively. The calibration curves were linear in the concentration ranges of 0.3-50.0 and 0.4-50.0 μg/L with the coefficients of determination of 0.9999 and 0.9995 for albendazole and triclabendazole, respectively. The interday and intraday relative standard deviations for albendazole and triclabendazole at three concentration levels (1.0, 10.0, and 30.0 μg/L) were in the range of 6.0-11.0 and 5.0-7.9%, respectively. The developed method was successfully applied to determine albendazole and triclabendazole in water, milk, honey, and urine samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of ring-shaped light fields with orbital angular momentum using a modal type liquid crystal spatial modulator

NASA Astrophysics Data System (ADS)

Kotova, S. P.; Mayorova, A. M.; Samagin, S. A.

2018-05-01

Techniques for forming vortex light fields using a modal type liquid crystal spatial modulator were proposed. An orbital angular momentum of light passing through the modulator or reflecting from it appears as a result of the jump in the profile of phase delay by means of using special configurations of contact electrodes and predetermined values of applying voltages. The features of the generated vortex beams and capabilities for their control were simulated.

Ion-pair vortex assisted liquid-liquid microextraction with back extraction coupled with high performance liquid chromatography-UV for the determination of metformin in plasma.

PubMed

Alshishani, Anas; Makahleh, Ahmad; Yap, Hui Fang; Gubartallah, Elbaleeq Adam; Salhimi, Salizawati Muhamad; Saad, Bahruddin

2016-12-01

A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150µL 1-octanol containing 0.2M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20µL of 0.075M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60s vortexing and 2min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using C1 column (250mm×4.6mm×10µm) and detected at 235nm. The method was validated and calibration curve was linear with r 2 >0.99 over the range of 20-2000µgL -1 . The limits of detection and quantitation were 1.4 and 4.1µgL -1 , respectively. The accuracy was within 94.8-108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Experimental study of flash boiling spray vaporization through quantitative vapor concentration and liquid temperature measurements

NASA Astrophysics Data System (ADS)

Zhang, Gaoming; Hung, David L. S.; Xu, Min

2014-08-01

Flash boiling sprays of liquid injection under superheated conditions provide the novel solutions of fast vaporization and better air-fuel mixture formation for internal combustion engines. However, the physical mechanisms of flash boiling spray vaporization are more complicated than the droplet surface vaporization due to the unique bubble generation and boiling process inside a superheated bulk liquid, which are not well understood. In this study, the vaporization of flash boiling sprays was investigated experimentally through the quantitative measurements of vapor concentration and liquid temperature. Specifically, the laser-induced exciplex fluorescence technique was applied to distinguish the liquid and vapor distributions. Quantitative vapor concentration was obtained by correlating the intensity of vapor-phase fluorescence with vapor concentration through systematic corrections and calibrations. The intensities of two wavelengths were captured simultaneously from the liquid-phase fluorescence spectra, and their intensity ratios were correlated with liquid temperature. The results show that both liquid and vapor phase of multi-hole sprays collapse toward the centerline of the spray with different mass distributions under the flash boiling conditions. Large amount of vapor aggregates along the centerline of the spray to form a "gas jet" structure, whereas the liquid distributes more uniformly with large vortexes formed in the vicinity of the spray tip. The vaporization process under the flash boiling condition is greatly enhanced due to the intense bubble generation and burst. The liquid temperature measurements show strong temperature variations inside the flash boiling sprays with hot zones present in the "gas jet" structure and vortex region. In addition, high vapor concentration and closed vortex motion seem to have inhibited the heat and mass transfer in these regions. In summary, the vapor concentration and liquid temperature provide detailed information concerning the heat and mass transfer inside flash boiling sprays, which is important for the understanding of its unique vaporization process.

Texas A&M vortex type phase separator

NASA Astrophysics Data System (ADS)

Best, Frederick

2000-01-01

Phase separation is required for regenerative biological and chemical process systems as well as thermal transport and rejection systems. Liquid and gas management requirements for future spacecraft will demand small, passive systems able to operate over wide ranges of inlet qualities. Conservation and recycling of air and water is a necessary part of the construction and operation of the International Space Station as well as future long duration space missions. Space systems are sensitive to volume, mass, and power. Therefore, it is necessary to develop a method to recycle wastewater with minimal power consumption. Regenerative life support systems currently being investigated require phase separation to separate the liquid from the gas produced. The microgravity phase separator designed and fabricated at Texas A&M University relies on centripetal driven buoyancy forces to form a gas-liquid vortex within a fixed, right-circular cylinder. Two-phase flow is injected tangentially along the inner wall of this cylinder producing a radial acceleration gradient. The gradient produced from the intrinsic momentum of the injected mixture results in a rotating flow that drives the buoyancy process by the production of a hydrostatic pressure gradient. Texas A&M has flown several KC-135 flights with separator. These flights have included scaling studies, stability and transient investigations, and tests for inventory instrumentation. Among the hardware tested have been passive devices for separating mixed vapor/liquid streams into single-phase streams of vapor only and liquid only. .

A green ionic liquid-based vortex-forced MSPD method for the simultaneous determination of 5-HMF and iridoid glycosides from Fructus Corni by ultra-high performance liquid chromatography.

PubMed

Du, Kunze; Li, Jin; Bai, Yun; An, Mingrui; Gao, Xiu-Mei; Chang, Yan-Xu

2018-04-01

A simple and green ionic liquid-based vortex-forced matrix solid phase dispersion (IL-VFMSPD) method was presented to simultaneously extract 5-hydroxymethyl furfurol (5-HMF) and iridoid glycosides in Fructus Corni by ultra-high performance liquid chromatography. Ionic liquid was used as a green elution reagent in vortex-forced MSPD process. A few parameters such as the type of ionic liquid, the type of sorbent, ratio of sample to sorbent, the concentration and volume of ionic liquid, grinding time and vortex time, were investigated in detail and an orthogonal design experiment was introduced to confirm the best conditions in this procedure. With the final optimized method, the recoveries of the target compounds in Fructus Corni were in the range of 95.2-103% (RSD<5.0%) and the method displayed a good linearity within the range of 0.8-200 μg mL -1 for morroniside, sweroside, loganin, cornuside and 1.2-300 μg mL -1 for 5-HMF. The limits of detection ranged from 0.02 to 0.08 μg mL -1 for all compounds. The results showed that the newly established method was efficiently applied to extract and determine iridoid glycosides and 5-HMF for quality control of Fructus Corni. Copyright © 2017 Elsevier Ltd. All rights reserved.

Entanglement of solid vortex matter: a boomerang-shaped reduction forced by disorder in interlayer phase coherence in Bi2Sr2CaCu2O8+y.

PubMed

Kato, T; Shibauchi, T; Matsuda, Y; Thompson, J R; Krusin-Elbaum, L

2008-07-11

We present evidence for entangled solid vortex matter in a glassy state in a layered superconductor Bi2Sr2CaCu2O8+y containing randomly splayed linear defects. The interlayer phase coherence--probed by the Josephson plasma resonance--is enhanced at high temperatures, reflecting the recoupling of vortex liquid by the defects. At low temperatures in the vortex solid state, the interlayer coherence follows a boomerang-shaped reentrant temperature path with an unusual low-field decrease in coherence, indicative of meandering vortices. We uncover a distinct temperature scaling between in-plane and out-of-plane critical currents with opposing dependencies on field and time, consistent with the theoretically proposed "splayed-glass" state.

Vortex- and CO2 -gas-assisted liquid-liquid microextraction with salt addition for the high-performance liquid chromatographic determination of furanic compounds in concentrated juices and dried fruits.

PubMed

Abu-Bakar, Nur-Bahiyah; Makahleh, Ahmad; Saad, Bahruddin

2016-03-01

A novel microextraction method based on vortex- and CO2 -assisted liquid-liquid microextraction with salt addition for the isolation of furanic compounds (5-hydroxymethyl-2-furaldehyde, 5-methyl-2-furaldehyde, 2-furaldehyde, 3-furaldehyde, 2-furoic and 3-furoic acids) was developed. Purging the sample with CO2 was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C18 column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r(2) >0.999), low detection limits (0.08-1.9 μg/L) and good recoveries (80.7-122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theory of the vortex matter transformations in high-Tc superconductor YBCO.

PubMed

Li, Dingping; Rosenstein, Baruch

2003-04-25

Flux line lattice in type II superconductors undergoes a transition into a "disordered" phase such as vortex liquid or vortex glass, due to thermal fluctuations and random quenched disorder. We quantitatively describe the competition between the thermal fluctuations and the disorder using the Ginzburg-Landau approach. The following T-H phase diagram of YBCO emerges. There are just two distinct thermodynamical phases, the homogeneous and the crystalline one, separated by a single first order transition line. The line, however, makes a wiggle near the experimentally claimed critical point at 12 T. The "critical point" is reinterpreted as a (noncritical) Kauzmann point in which the latent heat vanishes and the line is parallel to the T axis. The magnetization, the entropy, and the specific heat discontinuities at melting compare well with experiments.

Non-equlibrium relaxation of vortex lines in disordered type-II superconductors

NASA Astrophysics Data System (ADS)

Dobramysl, Ulrich; Assi, Hiba; Pleimling, Michel; T&äUber, Uwe C.

2013-03-01

Vortex matter in disordered type-II superconductors display a remarkable wealth of behavior, ranging from hexagonally arranged crystals and a vortex liquid to glassy phases. The type and strength of the disorder has a profound influence on the structural properties of the vortex matter: Randomly distributed weak point pinning sites lead to the destruction of long range order and a Bragg glass phase; correlated, columnar disorder can yield a Bose glass phase with infinite tilt modulus. We employ a three-dimensional elastic line model and apply a Langevin molecular dynamics algorithm to simulate the dynamics of vortex lines in a dissipative medium. We investigate the relaxation of a system of lines that were initially prepared in an out-of-equilibrium state and characterize the transient behavior via two-time quantities. We vary the disorder type and strength and compare our results for random and columnar disorder. Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-09ER46613.

Advection within side-by-side liquid micro-cylinders in a cross-flow

NASA Astrophysics Data System (ADS)

Dong, Qingming; Sau, Amalendu

2017-11-01

The gaseous SO2 entrainment from outer air stream and dispersion in binary and ternary liquid micro-cylinders appearing side-by-side are examined hereby. The separation/attachment regulated non-uniform interfacial momentum exchange creates main stream driven "primary" and shear reversed "secondary" vortices in the liquid cylinders. At separation points, the sense of rotation of the generated "primary-secondary" vortex pair remains inward directed. We define such a vortex pair as the "inflow" type. However, at stagnation or attachment points, the sense of rotation of a "primary-primary" or "secondary-secondary" vortex pair remains outward directed, and such a vortex pair is defined as the "outflow" type. For the coupled water cylinders facing an oncoming stream contaminated by gaseous SO2, its absorption and internal transport are effectively controlled by dominant "inflow" and "outflow" natured dynamics of the said vortex pairs, besides by diffusion. The evolving "inflow" natured "primary-secondary" vortex pairs at separation points actively entrain the outer SO2, whereas the "outflow" natured vortex-pairs oppose SO2 entry through the stagnation regions. Moreover, the blockage induced steady-symmetric, steady-deflected, and flip-flopping air-jets through gaps, for varied gap-ratio (1 ≤ G/R ≤ 4) and Reynolds number (30 ≤ Re ≤ 160), create distinctive impact both on quantitative SO2 absorption (mso2 ') and convective nature of the SO2 transport in upper, lower, and middle cylinders, by virtue of modified strength and size of the inflow and outflow paired vortices. The present study shows that the tiny "secondary vortices" play important roles in SO2 entrainment and in effectively controlling the local absorption rate Rs o2. The sudden acceleration and upward/downward deflection of gap-flows enhanced near-neck advective SO2 entrainment by suitably strengthening the "inflow" natured local vortex dynamics. Conversely, for the reduced size of secondary vortices, the saturation becomes delayed. In addition, for decreased vertical spacing of micro-cylinders (R = 40 μm) falling below the diameter-length "2R," the SO2 absorption (mso2 ') only gets slower. We provide extensive analysis of two-phase transport phenomena in terms of interactive shear-stress, pressure, and characteristic time-ratio "Tr" of advection-diffusion processes, for varied G/R, Re, and liquid phase Peclet number "Pel" (96 ≤ Pel ≤ 1333), to present a better insight into the governing physics.

Vortex lattices and defect-mediated viscosity reduction in active liquids

NASA Astrophysics Data System (ADS)

Slomka, Jonasz; Dunkel, Jorn

2016-11-01

Generic pattern-formation and viscosity-reduction mechanisms in active fluids are investigated using a generalized Navier-Stokes model that captures the experimentally observed bulk vortex dynamics in microbial suspensions. We present exact analytical solutions including stress-free vortex lattices and introduce a computational framework that allows the efficient treatment of previously intractable higher-order shear boundary conditions. Large-scale parameter scans identify the conditions for spontaneous flow symmetry breaking, defect-mediated low-viscosity phases and negative-viscosity states amenable to energy harvesting in confined suspensions. The theory uses only generic assumptions about the symmetries and long-wavelength structure of active stress tensors, suggesting that inviscid phases may be achievable in a broad class of non-equilibrium fluids by tuning confinement geometry and pattern scale selection.

Direct generation of abruptly focusing vortex beams using a 3/2 radial phase-only pattern.

PubMed

Davis, Jeffrey A; Cottrell, Don M; Zinn, Jonathan M

2013-03-20

Abruptly focusing Airy beams have previously been generated using a radial cubic phase pattern that represents the Fourier transform of the Airy beam. The Fourier transform of this pattern is formed using a system length of 2f, where f is the focal length of the Fourier transform lens. In this work, we directly generate these abruptly focusing Airy beams using a 3/2 radial phase pattern encoded onto a liquid crystal display. The resulting optical system is much shorter. In addition, we can easily produce vortex patterns at the focal point of these beams. Experimental results match theoretical predictions.

Separation Of Liquid And Gas In Zero Gravity

NASA Technical Reports Server (NTRS)

Howard, Frank S.; Fraser, Wilson S.

1991-01-01

Pair of reports describe scheme for separating liquid from gas so liquid could be pumped. Designed to operate in absence of gravitation. Jet of liquid, gas, or liquid/gas mixture fed circumferentially into cylindrical tank filled with liquid/gas mixture. Jet starts liquid swirling. Swirling motion centrifugally separates liquid from gas. Liquid then pumped from tank at point approximately diametrically opposite point of injection of jet. Vortex phase separator replaces such devices as bladders and screens. Requires no components inside tank. Pumps for gas and liquid outside tank and easily accessible for maintenance and repairs.

Particle-vortex symmetric liquid

NASA Astrophysics Data System (ADS)

Mulligan, Michael

2017-01-01

We introduce an effective theory with manifest particle-vortex symmetry for disordered thin films undergoing a magnetic field-tuned superconductor-insulator transition. The theory may enable one to access both the critical properties of the strong-disorder limit, which has recently been confirmed by Breznay et al. [Proc. Natl. Acad. Sci. USA 113, 280 (2016), 10.1073/pnas.1522435113] to exhibit particle-vortex symmetric electrical response, and the nearby metallic phase discovered earlier by Mason and Kapitulnik [Phys. Rev. Lett. 82, 5341 (1999), 10.1103/PhysRevLett.82.5341] in less disordered samples. Within the effective theory, the Cooper-pair and field-induced vortex degrees of freedom are simultaneously incorporated into an electrically neutral Dirac fermion minimally coupled to a (emergent) Chern-Simons gauge field. A derivation of the theory follows upon mapping the superconductor-insulator transition to the integer quantum Hall plateau transition and the subsequent use of Son's particle-hole symmetric composite Fermi liquid. Remarkably, particle-vortex symmetric response does not require the introduction of disorder; rather, it results when the Dirac fermions exhibit vanishing Hall effect. The theory predicts approximately equal (diagonal) thermopower and Nernst signal with a deviation parameterized by the measured electrical Hall response at the symmetric point.

Acoustically-Enhanced Direct Contact Vapor Bubble Condensation

NASA Astrophysics Data System (ADS)

Boziuk, Thomas; Smith, Marc; Glezer, Ari

2017-11-01

Rate-limited, direct contact vapor condensation of vapor bubbles that are formed by direct steam injection through a nozzle in a quiescent subcooled liquid bath is accelerated using ultrasonic (MHz-range) actuation. A submerged, low power actuator produces an acoustic beam whose radiation pressure deforms the liquid-vapor interface, leading to the formation of a liquid spear that penetrates the vapor bubble to form a vapor torus with a significantly larger surface area and condensation rate. Ultrasonic focusing along the spear leads to the ejection of small, subcooled droplets through the vapor volume that impact the vapor-liquid interface and further enhance the condensation. High-speed Schlieren imaging of the formation and collapse of the vapor bubbles in the absence and presence of actuation shows that the impulse associated with the collapse of the toroidal volume leads to the formation of a turbulent vortex ring in the liquid phase. Liquid motions near the condensing vapor volume are investigated in the absence and presence of acoustic actuation using high-magnification PIV and show the evolution of a liquid jet through the center of the condensing toroidal volume and the formation and advection of vortex ring structures whose impulse appear to increase with temperature difference between the liquid and vapor phases. High-speed image processing is used to assess the effect of the actuation on the temporal and spatial variations in the characteristic scales and condensation rates of the vapor bubbles.

High-efficiency and flexible generation of vector vortex optical fields by a reflective phase-only spatial light modulator.

PubMed

Cai, Meng-Qiang; Wang, Zhou-Xiang; Liang, Juan; Wang, Yan-Kun; Gao, Xu-Zhen; Li, Yongnan; Tu, Chenghou; Wang, Hui-Tian

2017-08-01

The scheme for generating vector optical fields should have not only high efficiency but also flexibility for satisfying the requirements of various applications. However, in general, high efficiency and flexibility are not compatible. Here we present and experimentally demonstrate a solution to directly, flexibly, and efficiently generate vector vortex optical fields (VVOFs) with a reflective phase-only liquid crystal spatial light modulator (LC-SLM) based on optical birefringence of liquid crystal molecules. To generate the VVOFs, this approach needs in principle only a half-wave plate, an LC-SLM, and a quarter-wave plate. This approach has some advantages, including a simple experimental setup, good flexibility, and high efficiency, making the approach very promising in some applications when higher power is need. This approach has a generation efficiency of 44.0%, which is much higher than the 1.1% of the common path interferometric approach.

Active suppression of vortex-driven combustion instability using controlled liquid-fuel injection

NASA Astrophysics Data System (ADS)

Pang, Bin

Combustion instabilities remain one of the most challenging problems encountered in developing propulsion and power systems. Large amplitude pressure oscillations, driven by unsteady heat release, can produce numerous detrimental effects. Most previous active control studies utilized gaseous fuels to suppress combustion instabilities. However, using liquid fuel to suppress combustion instabilities is more realistic for propulsion applications. Active instability suppression in vortex-driven combustors using a direct liquid fuel injection strategy was theoretically established and experimentally demonstrated in this dissertation work. Droplet size measurements revealed that with pulsed fuel injection management, fuel droplet size could be modulated periodically. Consequently, desired heat release fluctuation could be created. If this oscillatory heat release is coupled with the natural pressure oscillation in an out of phase manner, combustion instabilities can be suppressed. To identify proper locations of supplying additional liquid fuel for the purpose of achieving control, the natural heat release pattern in a vortex-driven combustor was characterized in this study. It was found that at high Damkohler number oscillatory heat release pattern closely followed the evolving vortex front. However, when Damkohler number became close to unity, heat release fluctuation wave no longer coincided with the coherent structures. A heat release deficit area was found near the dump plane when combustor was operated in lean premixed conditions. Active combustion instability suppression experiments were performed in a dump combustor using a controlled liquid fuel injection strategy. High-speed Schlieren results illustrated that vortex shedding plays an important role in maintaining self-sustained combustion instabilities. Complete combustion instability control requires total suppression of these large-scale coherent structures. The sound pressure level at the excited dominant frequency was reduced by more than 20 dB with controlled liquid fuel injection method. Scaling issues were also investigated in this dump combustor to test the effectiveness of using pulsed liquid fuel injection strategies to suppress instabilities at higher power output conditions. With the liquid fuel injection control method, it was possible to suppress strong instabilities with initial amplitude of +/-5 psi down to the background noise level. The stable combustor operating range was also expanded from equivalence ratio of 0.75 to beyond 0.9.

Non-ionic detergent Triton X-114 Based vortex- synchronized matrix solid-phase dispersion method for the simultaneous determination of six compounds with various polarities from Forsythiae Fructus by ultra high-performance liquid chromatography.

PubMed

Du, Kunze; Li, Jin; Tian, Fei; Chang, Yan-Xu

2018-02-20

A simple nonionic detergent - based vortex- synchronized matrix solid-phase dispersion (ND-VSMSPD) method was developed to extract bioactive compounds in Forsythiae Fructus coupled with ultra high-performance liquid chromatography (UHPLC). Nonionic detergent Triton 114 was firstly used as a green elution reagent in vortex- synchronized MSPD procedure. The optimum parameters were investigated to attain the best results, including Florisil as sorbent, 2mL 10% (v/v) nonionic detergent Triton X-114 as the elution reagent, 1:1 of sample/sorbent ratio, grinding for 3min, and whirling for 2min. The recoveries of the six compounds in Forsythiae Fructus were in the range of 95-104% (RSD <4.6%) and the method displayed a good linearity within the range of 0.08-20μgmL -1 for caffeic acid, 0.6-150μgmL -1 for forsythoside A, 0.4-100μgmL -1 phillyrin, 0.2-50μgmL -1 for quercetin, isorhamnetin and arctigenin (r≥0.999). It was proved that the extraction yields of almost all compounds attained by the established vortex- synchronized MSPD, which required lower sample, reagent and time, were higher than the normal MSPD and the traditional ultrasonic-assisted extraction. Consequently, this developed vortex- synchronized MSPD coupled with simple UHPLC method could be efficiently applies to extract and analyze the target compounds in real Forsythiae Fructus samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Vortex-glass state in the isovalent optimally doped pnictide superconductor BaFe2(As0.68P0.32)2

NASA Astrophysics Data System (ADS)

Salem-Sugui, S., Jr.; Mosqueira, J.; Alvarenga, A. D.; Sóñora, D.; Crisan, A.; Ionescu, A. M.; Sundar, S.; Hu, D.; Li, S.-L.; Luo, H.-Q.

2017-05-01

We report on isochamp magneto-resistivity and ac susceptibility curves obtained in a high-quality single crystal of the isovalent optimally doped pnictide BaFe2(As{}0.68P{}0.32)2 with superconducting temperature T c = 27.8 K for H∥c-axis. Plots of the logarithmic derivative of the resistivity curves allowed the identification of a vortex-glass (VG) phase and to obtain the values of the critical glass temperature T g, the temperature T * marking the transition to the liquid phase and of the critical exponent s. The presence of the VG phase is confirmed by detailed measurements of the third harmonic signal of the ac magnetic susceptibility. The modified VG model was successfully applied to the data allowing the obtention of the temperature independent VG activation energy U b . The activation energy U 0 obtained from the Arrhenius plots in the flux-flow region are compared with U b and with U 0 obtained from flux-creep measurements on a M(H) isothermal in the same sample. A phase diagram of the studied sample is constructed showing the T g glass line, the T * line representing a transition (melting) to the liquid phase, the mean field temperature T c(H) line and the H p line obtained from the peaks in isothermal critical current, J c(H) curves, which are explained in terms of a softening of the vortex lattice. The glass line was fitted by a theory presented in the literature which considers the effect of disorder.

Simultaneous determination of furfural and its degradation products, furoic acid and maleic acid, in transformer oil by the reversed-phase vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography.

PubMed

Wang, Yifan; Li, Haiyan; Yang, Zhen; Zhang, Weijie; Hua, Jia

2017-12-01

To explore why the use of furfural as a transformer oil-paper insulation aging characteristic is problematic in real world application, we developed a method for the simultaneous determination of furfural, furoic acid, and maleic acid in transformer oil by reversed-phase vortex-assisted liquid-liquid microextraction combined with high-performance liquid chromatography. The conditions for the proposed method were optimized, and the obtained extract can be directly analyzed by high-performance liquid chromatography. The detection limits (signal-to-noise ratio = 3) of the method ranged from 1.0 to 4.6 μg/L, the enrichment factors for furfural, furoic acid, maleic acid, and fumaric acid were 4.6, 25.1, 15.6, and 17.5, respectively, and the recovery rates for three analytes (fumaric acid was undetected) range from 82.1 to 106.2%. The contents of furfural, furoic acid, and maleic acid resulted from accelerated aging of transformer insulation oil-paper were measured using the present method for the first time, and the aging samples were analyzed by liquid chromatography with mass spectrometry for the identification of furoic acid and maleic acid in the aging transformer oil samples. Using the optimal method, the target products of samples at different aging time were tracked and measured. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of micellar extraction combined with ionic liquid based vortex-assisted liquid-liquid microextraction and modified quick, easy, cheap, effective, rugged, and safe method for the determination of difenoconazole in cowpea.

PubMed

Chen, Xiaochu; Bian, Yanli; Liu, Fengmao; Teng, Peipei; Sun, Pan

2017-10-06

Two simple sample pretreatment for the determination of difenoconazole in cowpea was developed including micellar extraction combined with ionic liquid based vortex-assisted liquid-liquid microextraction (ME-IL-VALLME) prior to high performance liquid chromatography (HPLC), and modified quick, easy, cheap, effective, rugged, and safe method (QuEChERS) coupled with HPLC-MS/MS. In ME-IL-VALLME method, the target analyte was extracted by surfactant Tween 20 micellar solution, then the supernatant was diluted with 3mL water to decrease the solubility of micellar solution. Subsequently, the vortex-assisted liquid-liquid microextraction (VALLME) procedure was performed in the diluted extraction solution by using the ionic liquid of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF 6 ) as the extraction solvent and Tween 20 as an emulsifier to enhance the dispersion of the water-immiscible ionic liquid into the aqueous phase. Parameters that affect the extraction have been investigated in both methods Under the optimum conditions, the limits of quantitation were 0.10 and 0.05mgkg -1 , respectively. And good linearity was achieved with the correlation coefficient higher than 0.9941. The relative recoveries ranged from 78.6 to 94.8% and 92.0 to 118.0% with the relative standard deviations (RSD) of 7.9-9.6% and 1.2-3.2%, respectively. Both methods were quick, simple and inexpensive. However, the ME-IL-VALLME method provides higher enrichment factor compared with conventional QuEChERS method. The ME-IL-VALLME method has a strong potential for the determination of difenoconazole in complex vegetable matrices with HPLC. Copyright © 2017 Elsevier B.V. All rights reserved.

The Josephson plasma resonance as a “scattering” probe of vortex correlation in the liquid state

NASA Astrophysics Data System (ADS)

Ong, N. P.; Bayracki, Sibel P.; Tsui, Ophelia K. C.; Kishio, K.; Watauchi, S.

1997-12-01

In the vortex liquid state the Josephson plasma frequency ωp is strongly affected by fluctuations in the vortex pancakes. We have measured in detail the variation of ωp with field B and tilt angle θ in Bi 2Sr 2CaCu 2O 8. We compare the data with Koshelev's expression relating ωp to the correlation function of the local phase S1. The agreement is quite close for θ > 1°, provided f varies with B with a weak exponent ( f measures the number of pancakes within a correkated area). A scattering picture is introduced to clarify how the plasma resonance is equivalent to a Fourier transform of | S1| 2. From the fit, we fin that, at 50 K and 1 T, f ≈ 1.4 pancakes, Jc0 equals 4160 A/cm 2 and = 0.028. Deviations observed when B is aligned with the planes are discussed.

Topological phase transition of decoupling quasi-two-dimensional vortex pairs in La1- y Sm y MnO3 + δ ( y = 0.85, 1.0)

NASA Astrophysics Data System (ADS)

Bukhanko, F. N.; Bukhanko, A. F.

2016-10-01

Characteristic signs of the universal Nelson-Kosterlitz jump of the superconducting liquid density in the temperature dependences of the magnetization of La1- y Sm y MnO3 + δ samples with samarium concentrations y = 0.85 and 1.0, which are measured in magnetic fields 100 Oe ≤ H ≤ 3.5 kOe, are detected. As the temperature increases, the sample with y = 0.85 exhibits a crescent-shaped singularity in the dc magnetization curve near the critical temperature of decoupling vortex-antivortex pairs ( T KT ≡ T c ≈ 43 K), which is independent of measuring magnetic field H and is characteristic of the dissociation of 2D vortex pairs. A similar singularity is also detected in the sample with a samarium concentration y = 1.0 at a significantly lower temperature ( T KT ≈ 12 K). The obtained experimental results are explained in terms of the topological Kosterlitz-Thouless phase transition of dissociation of 2D vortex pairs in a quasi-two-dimensional weak Josephson coupling network.

The VOrtex Ring Transit EXperiment (VORTEX) GAS project

NASA Technical Reports Server (NTRS)

Bilen, Sven G.; Langenderfer, Lynn S.; Jardon, Rebecca D.; Cutlip, Hansford H.; Kazerooni, Alexander C.; Thweatt, Amber L.; Lester, Joseph L.; Bernal, Luis P.

1995-01-01

Get Away Special (GAS) payload G-093, also called VORTEX (VOrtex Ring Transit EXperiment), is an investigation of the propagation of a vortex ring through a liquid-gas interface in microgravity. This process results in the formation of one or more liquid droplets similar to earth based liquid atomization systems. In the absence of gravity, surface tension effects dominate the drop formation process. The Shuttle's microgravity environment allows the study of the same fluid atomization processes as using a larger drop size than is possible on Earth. This enables detailed experimental studies of the complex flow processes encountered in liquid atomization systems. With VORTEX, deformations in both the vortex ring and the fluid surface will be measured closely for the first time in a parameters range that accurately resembles liquid atomization. The experimental apparatus will record images of the interactions for analysis after the payload has been returned to earth. The current design of the VORTEX payload consists of a fluid test cell with a vortex ring generator, digital imaging system, laser illumination system, computer based controller, batteries for payload power, and an array of housekeeping and payload monitoring sensors. It is a self-contained experiment and will be flown on board the Space Shuttle in a 5 cubic feet GAS canister. The VORTEX Project is entirely run by students at the University of Michigan but is overseen by a faculty advisor acting as the payload customer and the contact person with NASA. This paper summarizes both the technical and programmatic aspects of the VORTEX Project.

Negative vortices: The formation of vortex rings with reversed rotation in viscoelastic liquids

NASA Astrophysics Data System (ADS)

Palacios-Morales, Carlos; Barbosa, Christophe; Solorio, Francisco; Zenit, Roberto

2015-05-01

The formation process of vortex rings in a viscoelastic liquid is studied experimentally considering a piston-cylinder arrangement. Initially, a vortex ring begins to form as fluid is injected from the cylinder into the tank in a manner similar to that observed for Newtonian liquids. For later times, when the piston ceases its motion, the flow changes dramatically. A secondary vortex with reversed spinning direction appears and grows to be as large in size as the original one. The formation process is studied by contrasting the evolution with that obtained for Newtonian liquids with equivalent Reynolds numbers and stroke ratios. We argue that the reversing flow, or negative vortex, results from the combined action of shear and extension rates produced during the vortex formation, in a process similar to that observed behind ascending bubbles and falling spheres in viscoelastic media.

Formation of gapless Z 2 spin liquid phase manganites in the (Sm1- y Gd y )0.55Sr0.45MnO3 system in zero magnetic field: Topological phase transitions to states with low and high density of 2D-vortex pairs induced by the magnetic field

NASA Astrophysics Data System (ADS)

Bukhan'ko, F. N.; Bukhan'ko, A. F.

2017-12-01

The evolution of the ground state of the manganese spin ensemble in the (Sm1- y Gd y )0.55Sr0.45MnO3 in the case of isovalent substitution of rare-earth samarium ions with large radii with gadolinium ions with significantly smaller radii is studied. The measured temperature dependences of the ac magnetic susceptibility and the field dependences of the dc magnetizations are analyzed using the Heisenberg-Kitaev model describing the transition from the ordered spin state with classical isotropic AFM exchange to the frustrated spin state with quantum highly anisotropic FM exchange. A continuous transition from the 3D ferromagnetic state of manganese spins in the initial sample with y = 0 to zigzag AFM ordering of CE-type spins in ab planes for y = 0.5, coexisting in samples with y = 0.5, 0.6, and 0.7 at temperatures below T N ≅ 48.5 K with a disordered phase such as a quantum Griffiths phase is identified. As the gadolinium concentration further increases, the CE-type zigzag AFM structure is molten, which leads to the appearance of an unusual phase in Gd0.55Sr0.45MnO3 in the temperature range close to the absolute zero. This phase has characteristic features of a gapless Z 2 quantum spin liquid in zero external magnetic field. The step changes in the magnetization isotherms measured at 4.2 K in the field range of ±75 kOe are explained by quantum phase transitions of the Z 2 spin liquid to a phase with topological order in weak magnetic fields and a polarized phase in strong fields. The significant difference between critical fields and magnetization jumps in isotherms indicates the existence of hysteretic phenomena in quantum spin liquid magnetization-demagnetization processes caused by the difference between localization-delocalization of 2D vortex pairs induced by a magnetic field in a quantum spin liquid with disorder.

Phase diagrams of flux lattices with disorder

NASA Astrophysics Data System (ADS)

Giamarchi, T.; Le Doussal, P.

1997-03-01

We review the prediction, made in a previous work [T. Giamarchi and P. Le Doussal, Phys. Rev. B 52, 1242 (1995)], that the phase diagram of type-II superconductors consists of a topologically ordered Bragg glass phase at low fields undergoing a transition at higher fields into a vortex glass or a liquid. We estimate the position of the phase boundary using a Lindemann criterion. We find that the proposed theory is compatible with recent experiments on superconductors. Further experimental consequences are investigated.

Vortex-assisted liquid-liquid microextraction for the rapid screening of short-chain chlorinated paraffins in water.

PubMed

Chang, Chia-Yu; Chung, Wu-Hsun; Ding, Wang-Hsien

2016-01-01

The rapid screening of trace levels of short-chain chlorinated paraffins in various aqueous samples was performed by a simple and reliable procedure based on vortex-assisted liquid-liquid microextraction combined with gas chromatography and electron capture negative ionization mass spectrometry. The optimal vortex-assisted liquid-liquid microextraction conditions for 20 mL water sample were as follows: extractant 400 μL of dichloromethane; vortex extraction time of 1 min at 2500 × g; centrifugation of 3 min at 5000 × g; and no ionic strength adjustment. Under the optimum conditions, the limit of quantitation was 0.05 μg/L. Precision, as indicated by relative standard deviations, was less than 9% for both intra- and inter-day analysis. Accuracy, expressed as the mean extraction recovery, was above 91%. The vortex-assisted liquid-liquid microextraction with gas chromatography and electron capture negative ionization mass spectrometry method was successfully applied to quantitatively extract short-chain chlorinated paraffins from samples of river water and the effluent of a wastewater treatment plant, and the concentrations ranged from 0.8 to 1.6 μg/L. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mixed-state Hall effect of high-T(c) superconductors

NASA Astrophysics Data System (ADS)

Kang, Byeongwon

In this dissertation, we presented the study on the mixed-state Hall effect of high-Tc superconductors (HTSs). In order to understand the mechanisms of the puzzling phenomena in the mixed-state Hall effect of HTSs, the Hall sign anomaly and scaling behavior, Hall measurements are conducted in several HTS thin films. We investigate the mechanism of the sign reversal of the Hall resistivity in Tl-2201 films when the electronic band structure is varied through the underdoped, optimally doped, and overdoped regions. It is found that the Hall sign reversals are an intrinsic property of HTSs and determined by electronic band structure. Although pinning is not found to be the mechanism behind sign reversals, pinning can suppress the appearance of the Hall sign reversal. Therefore, it is concluded that two (or more) sign reversals are a generic behavior of HTSs. From a systematic study of the vortex phase diagram, we discover several new features of the vortex liquid. In the presence of pinning, the vortex-liquid phase can be divided into two regions, a glassy liquid (GL) where vortices remain correlated as manifested in non-Ohmic resistivity, and a regular liquid (RL) where resistivity becomes Ohmic as vortices become uncorrelated. The field dependence of the Hall angle is found to be linear in the RL and nonlinear in the GL. Generally the decoupling line (Hk- T), which is defined as a boundary between the GL and the RL, is lower than the depinning line (Hd-T). As pinning increases the Hk-T may approach the Hd-T, thus vortices are decoupled and depinned nearly simultaneously. For a weak pinning system, on the other hand, the Hk-T and the Hd-T are well separated so that single vortices remain pinned in the region Hk ≤ H ≥ Hd. The behavior of s xy is also investigated in the GL and the RL. In the GL s xy is observed to strongly depend on pinning due to the inter-vortex correlation whereas in the RL s xy is independent of pinning since the pinning effect is scaled out.

Vortex-Assisted Dispersive Micro-Solid Phase Extraction Using CTAB-Modified Zeolite NaY Sorbent Coupled with HPLC for the Determination of Carbamate Insecticides.

PubMed

Salisaeng, Pawina; Arnnok, Prapha; Patdhanagul, Nopbhasinthu; Burakham, Rodjana

2016-03-16

A vortex-assisted dispersive micro-solid phase extraction (VA-D-μ-SPE) based on cetyltrimethylammonium bromide (CTAB)-modified zeolite NaY was developed for preconcentration of carbamate pesticides in fruits, vegetables, and natural surface water prior to analysis by high performance liquid chromatography with photodiode array detection. The small amounts of solid sorbent were dispersed in a sample solution, and extraction occurred by adsorption in a short time, which was accelerated by vortex agitation. Finally, the sorbents were filtered from the solution, and the analytes were subsequently desorbed using an appropriate solvent. Parameters affecting the VA-D-μ-SPE performance including sorbent amount, sample volume, desorption solvent ,and vortex time were optimized. Under the optimum condition, linear dynamic ranges were achieved between 0.004-24.000 mg kg(-1) (R(2) > 0.9946). The limits of detection (LODs) ranged from 0.004-4.000 mg kg(-1). The applicability of the developed procedure was successfully evaluated by the determination of the carbamate residues in fruits (dragon fruit, rambutan, and watermelon), vegetables (cabbage, cauliflower, and cucumber), and natural surface water.

Calorimetric Study of Phase Transitions Involving Twist-Grain-Boundary TGB{A} and TGB{C} Phases

NASA Astrophysics Data System (ADS)

Navailles, L.; Garland, C. W.; Nguyen, H. T.

1996-09-01

High-resolution calorimetry has been used to determine the heat capacity and latent heat associated with phase transitions in the homologous series of chiral liquid crystals nF_2BTFO_1M_7 [ 3-fluoro-4(1-methylheptyloxy)4'-(4''-alkoxy-2'', 3''-difluorobenzoyloxy)tolane] . These compounds exhibit smectic-C^* (SmC^*), twist-grain-boundary (TGBA for n=10, TGBC for n=11, 12) and cholesteric (N^*) phases. All the phase transitions are first order with small to moderate latent heats. There is a large rounded excess heat capacity peak in the N^* phase that is consistent with the predicted appearance of short-range TGB order (chiral line liquid character). This is analogous to the development of an Abrikosov flux vortex liquid in type-II superconductors. Both the n=11 and 12 homologs exhibit two closely spaced transitions in the region where a single TGBC - N^* transition was expected. This suggests the existence of two thermodynamically distinct TGBC phases. Des exprériences de calorimétrie haute résolution ont été réalisées pour déterminer les chaleurs spécifiques et les chaleurs latentes associées aux transitions de phase des homologues de la série crystal liquide nF_2BTFO_1M_7: 3-fluoro-4[1-methyl-heptyloxy]4'-(4''-alcoxy-2'', 3''-difluorobenzoyloxy)tolanes. Ces produits présentent la phase smectique C^* (SmC^*), les phases à torsion par joint de grain (TGBA pour n=10 et TGBC pour n=11, 12) et la phase cholestérique (N^*). Toutes les transitions de phase sont du premier ordre. La chaleur latente associée à ces transitions est faibles ou modérée. Nous observons, dans la phase N^*, un grand pic arrondi qui est en accord avec les prédictions de l'apparition d'un ordre TGB à courte distance (liquide de ligne de dislocation). Ce phénomène est l'analogue du liquide de vortex dans les supraconducteurs de type II. Les composés n=11 et 12 présentent, dans la région où nous attendions une transition TGBC - N^* unique, deux transitions sur un très faible domaine de température. Ce résultat suggère l'existence de deux phases TGBC thermodynamiquement distinctes.

Evaluation of Commercial Off-the-Shelf and Government Off-the-Shelf Microclimate Cooling Systems

DTIC Science & Technology

2005-08-01

Appendix A - Request for Information (RFI) 23 Appendix B - Memorandum from Natick Soldier Center’s International Office 25 Appendix C - Cooling Power...Data Entry Forms 7 Figure 3. Evaporative Cooling Products 9 Figure 4. Passive Phase Change Product 10 Figure 5. Liquid Circulating...Microclimate Cooling System 13 Figure 6. Compressed Air Cooling Product 15 Figure 7. Vortex Tube 15 Figure 8. Active Phase

Superconducting properties and vortex dynamics of bismuth strontium calcium copper oxide nanoribbons with and without periodic array of nanoscale holes

NASA Astrophysics Data System (ADS)

Avci, Sevda

The distinguishing features of high-temperature superconducting materials are the dynamics of vortex matter in the mixed state which are greatly affected by the high anisotropy and the Josephson coupling between layers. Experiments have focused on investigating melting and dynamic phases of vortex matter with random pinning. However, the advancements in sample preparation techniques have made it possible to investigate the vortex matter with periodic pinnings, since it can serve as a model system to study periodic elastic media such as electron crystals driven on substrates with arrays of defects. It also offers the possibility to increase the critical current of a superconductor through a matching effect which represents itself as peaks (dips) in the field dependences of the critical current (magnetoresisance). This effect is due to the enhanced pinning strength at matching fields where the density of the flux quanta is equal to or multiple times that of the pins. This dissertation reports investigation on the dynamics of vortex matter with periodic pinning array by utilizing BSCCO-2212 crystalline nanoribbons containing periodic arrays of nanoscale holes. Systematic transport measurements reveal the existence of possible intermediate phases of a soft solid and/or a mixture of solid and liquid during melting for the melting transition from solid to a pure liquid. The results of this research demonstrate that the matching effect can be an effective tool in revealing the nature of various vortex phases during melting transition. In addition, anomalous resistive peaks below Tc and the effect of magnetic field orientation on superconductivity of BSCCO-2212 nanoribbons with array of nanoscale holes are also investigated. Angle-dependent magnetoresistances are scaled as H=Hthetacostheta. Therefore, only the perpendicular component of the magnetic field affects the superconductivity. Moreover, layers in BSCCO nanoribbons are lying in the a-b plane parallel to each other. Moreover, at large currents and fields, the resistance shows a non-monotonic dependence on temperature, even showing values that are higher than the normal state resistance for certain ranges of parameters. Observed behavior is attributed to the brick-wall morphology of the nanoribbons leading to a competition between normal and superconductive tunneling that is known to take place in granular superconductive systems.

Electrical and thermal transport properties of the electron-doped cuprate Sm2-x Ce x CuO4-y system

NASA Astrophysics Data System (ADS)

Scanderbeg, D. J.; Taylor, B. J.; Baumbach, R. E.; Paglione, J.; Maple, M. B.

2016-12-01

Electrical and thermal transport measurements were performed on thin films of the electron-doped superconductor Sm2-x Ce x CuO4-y (x  =  0.13  -  0.19) in order to study the evolving nature of the charge carriers from the under-doped to over-doped regime. A temperature versus cerium content (T  -  x) phase diagram has been constructed from the electrical transport measurements, yielding a superconducting region similar to that found for other electron-doped superconductors. Thermopower measurements show a dramatic change from the underdoped region (x  <  0.15) to the overdoped region (x  >  0.15). Application of the Fisher-Fisher-Huse (FFH) vortex glass scaling model to the magnetoresistance data was found to be insufficient to describe the data in the region of the vortex-solid to vortex-liquid transition. It was found instead that the modified vortex glass scaling model of Rydh, Rapp, and Anderson provided a good description of the data, indicating the importance of the applied field on the pinning landscape. A magnetic field versus temperature (H  -  T) phase diagram has also been constructed for the films with x≥slant 0.14 , displaying the evolution of the vortex glass melting lines H g (T) across the superconducting regime.

Antivortex Device for Multi-Outlet Liquid Reservoir

NASA Technical Reports Server (NTRS)

Grayson, Gary David (Inventor); Addison, Stephen Michael (Inventor)

2016-01-01

A liquid reservoir with a sump includes at least two outlet ports in fluid communication with a fluid conduit. An anti-vortex device includes a first plate extending across the at least two outlet ports and a second plate coupled to the first plate and extending substantially perpendicular to the first plate. The anti-vortex device is configured to disrupt formation of a vortex formed by liquid passing from the reservoir through said outlet ports.

Phase diagrams of vortex matter with multi-scale inter-vortex interactions in layered superconductors.

PubMed

Meng, Qingyou; Varney, Christopher N; Fangohr, Hans; Babaev, Egor

2017-01-25

It was recently proposed to use the stray magnetic fields of superconducting vortex lattices to trap ultracold atoms for building quantum emulators. This calls for new methods for engineering and manipulating of the vortex states. One of the possible routes utilizes type-1.5 superconducting layered systems with multi-scale inter-vortex interactions. In order to explore the possible vortex states that can be engineered, we present two phase diagrams of phenomenological vortex matter models with multi-scale inter-vortex interactions featuring several attractive and repulsive length scales. The phase diagrams exhibit a plethora of phases, including conventional 2D lattice phases, five stripe phases, dimer, trimer, and tetramer phases, void phases, and stable low-temperature disordered phases. The transitions between these states can be controlled by the value of an applied external field.

Generation of helical Ince-Gaussian beams with a liquid-crystal display.

PubMed

Bentley, Joel B; Davis, Jeffrey A; Bandres, Miguel A; Gutiérrez-Vega, Julio C

2006-03-01

We generate helical Ince-Gaussian (HIG) beams by using complex amplitude and phase masks encoded onto a liquid-crystal display (LCD). These beams display an intensity pattern consisting of elliptic rings, whose number and ellipticity can be controlled, and a phase exhibiting a number of in-line vortices, each with a unitary topological charge. We show experimental results that display the properties of these elliptic dark hollow beams. We introduce a novel interference technique for generating the object and reference beams by using a single LCD and show the vortex interference patterns. We expect that these HIG beams will be useful in optical trapping applications.

Generation of helical Ince-Gaussian beams with a liquid-crystal display

NASA Astrophysics Data System (ADS)

Bentley, Joel B.; Davis, Jeffrey A.; Bandres, Miguel A.; Gutiérrez-Vega, Julio C.

2006-03-01

We generate helical Ince-Gaussian (HIG) beams by using complex amplitude and phase masks encoded onto a liquid-crystal display (LCD). These beams display an intensity pattern consisting of elliptic rings, whose number and ellipticity can be controlled, and a phase exhibiting a number of in-line vortices, each with a unitary topological charge. We show experimental results that display the properties of these elliptic dark hollow beams. We introduce a novel interference technique for generating the object and reference beams by using a single LCD and show the vortex interference patterns. We expect that these HIG beams will be useful in optical trapping applications.

Cavity-induced artificial gauge field in a Bose-Hubbard ladder

NASA Astrophysics Data System (ADS)

Halati, Catalin-Mihai; Sheikhan, Ameneh; Kollath, Corinna

2017-12-01

We consider theoretically ultracold interacting bosonic atoms confined to quasi-one-dimensional ladder structures formed by optical lattices and coupled to the field of an optical cavity. The atoms can collect a spatial phase imprint during a cavity-assisted tunneling along a rung via Raman transitions employing a cavity mode and a transverse running wave pump beam. By adiabatic elimination of the cavity field we obtain an effective Hamiltonian for the bosonic atoms, with a self-consistency condition. Using the numerical density-matrix renormalization-group method, we obtain a rich steady-state diagram of self-organized steady states. Transitions between superfluid to Mott-insulating states occur, on top of which we can have Meissner, vortex liquid, and vortex lattice phases. Also a state that explicitly breaks the symmetry between the two legs of the ladder, namely, the biased-ladder phase, is dynamically stabilized. We investigate the influence that a trapping potential has on the stability of the self-organized phases.

Indication of Confirmation of Transition and Formation Boundary from Ordered to Disordered Flux Vortex Chain State in High-Tc Superconductors Y1Ba2Cu3O7- δ and Bi2Sr2Ca2Cu3O10 and New Low-Field Data Delineating Magnetic Transition in Gd1Ba2(Fe0.02Cu0.98)3O7- δ

NASA Astrophysics Data System (ADS)

Vezzoli, G. Christopher; Chen, Michaeline F.; Burke, Terence; Rosen, Carol

1996-08-01

Data are presented herein that support a phase boundary or quasi-phase-boundary delineating in Y1Ba2Cu3O7-δ and in Bi2Sr2Ca2Cu3O10 ceramic materials a transition from a vortex solid lattice to a line-flux disordered state that has been referred to as representing flux lattice melting to a flux liquid, but herein is interpreted not in terms of a liquid but in the form of a less-mobile `polymer'-like or entangled chain species. These data are derived from electrical resistance (r) versus applied magnetic field (H) measurements at various isotherms (T) corresponding to the zero resistance state of yttrium--barium--cuprate, and the mixed state foot regime of bismuth--strontium--calcium--cuprate. We interpret significant slope changes in r versus B at constant T in these materials to be indicative of the H-T conditions for a second-order or weakly first-order phase transition delineating the disordering of a flux lattice vortex solid. We believe that this technique is in ways more direct and at least as accurate as the conventional mechanical oscillator and vibrating magnetometer method to study the flux state. Additional very-low-field studies in Gd1Ba2(Fe0.02Cu0.98)3O7-δ, from 1 to 1000 mT, yield indication for what appears to be a magnetic transition at ca. 77 K at 575 mT, and possibly a second transition at 912 mT (also at ca. 77 K). These data points correspond well with the extrapolated low-field experimental magnetic phase transition boundary curve described at higher field herein (and by others using the mechanical technique), and also correspond well to theoretically predicted work regarding transition involving the vortex state.

Thermal reactor. [liquid silicon production from silane gas

NASA Technical Reports Server (NTRS)

Levin, H.; Ford, L. B. (Inventor)

1982-01-01

A thermal reactor apparatus and method of pyrolyticaly decomposing silane gas into liquid silicon product and hydrogen by-product gas is disclosed. The thermal reactor has a reaction chamber which is heated well above the decomposition temperature of silane. An injector probe introduces the silane gas tangentially into the reaction chamber to form a first, outer, forwardly moving vortex containing the liquid silicon product and a second, inner, rewardly moving vortex containing the by-product hydrogen gas. The liquid silicon in the first outer vortex deposits onto the interior walls of the reaction chamber to form an equilibrium skull layer which flows to the forward or bottom end of the reaction chamber where it is removed. The by-product hydrogen gas in the second inner vortex is removed from the top or rear of the reaction chamber by a vortex finder. The injector probe which introduces the silane gas into the reaction chamber is continually cooled by a cooling jacket.

Upward shift of the vortex solid phase in high-temperature-superconducting wires through high density nanoparticle addition

DOE PAGES

Miura, Masashi; Maiorov, Boris; Balakirev, Fedor F.; ...

2016-02-08

Here, we show a simple and effective way to improve the vortex irreversibility line up to very high magnetic fields (60T) by increasing the density of second phase BaZrO 3 nanoparticles. (Y 0.77,Gd 0.23)Ba 2Cu 3O y films were grown on metal substrates with different concentration of BaZrO 3 nanoparticles by the metal organic deposition method. We find that upon increase of the BaZrO 3 concentration, the nanoparticle size remains constant but the twin-boundary density increases. Up to the highest nanoparticle concentration (n ~ 1.3 × 10 22/m 3), the irreversibility field (H irr) continues to increase with no signmore » of saturation up to 60 T, although the vortices vastly outnumber pinning centers. We find extremely high H irr, namely H irr = 30 T (H||45°) and 24 T (H||c) at 65 K and 58 T (H||45°) and 45 T (H||c) at 50K. The difference in pinning landscape shifts the vortex solid-liquid transition upwards, increasing the vortex region useful for power applications, while keeping the upper critical field, critical temperature and electronic mass anisotropy unchanged.« less

Deep eutectic liquid organic salt as a new solvent for liquid-phase microextraction and its application in ligandless extraction and preconcentraion of lead and cadmium in edible oils.

PubMed

Karimi, Mehdi; Dadfarnia, Shayessteh; Shabani, Ali Mohammad Haji; Tamaddon, Fatemeh; Azadi, Davood

2015-11-01

Deep eutectic liquid organic salt was used as the solvent and a liquid phase microextraction (DES-LPME) combined with electrothermal atomic absorption spectrometry (ETAAS) was developed for separation, preconcentration and determination of lead and cadmium in edible oils. A 4:1 mixture of deep eutectic solvent and 2% nitric acid (200 µL) was added to an oil sample. The mixture was vortexed and transferred into a water bath at 50 °C and stirred for 5 minutes. After the extraction was completed, the phases were separated by centrifugation, and the enriched analytes in the deep eutectic solvent phase were determined by ETAAS. Under optimized extraction conditions and for an oil sample of 28 g, enhancement factors of 198 and 195 and limits of detection (defined as 3 Sb/m) of 8 and 0. 2 ng kg(-1) were achieved for lead and cadmium respectively. The method was successfully applied to the determination of lead and cadmium in various edible oils. Copyright © 2015. Published by Elsevier B.V.

Vortex Flows in the Liquid Layer and Droplets on a Vibrating Flexible Plate

NASA Astrophysics Data System (ADS)

Aleksandrov, Vladimir; Kopysov, Sergey; Tonkov, Leonid

2018-02-01

In certain conditions, in the layers and droplets of a liquid on a vibrating rectangular flexible plate, vortex flows are formed simultaneously with the excitation of capillary oscillations on the free surface of the liquid layers and droplets. Capillary oscillations in the form of two-dimensional standing waves form Faraday ripples on the free surface of the liquid layer. On the surface of the vibrating droplets, at the excitation of capillary oscillations a light spot reflected from a spotlight source moves along a trajectory in the form of a Lissajous figure observed with a microscope. When vortex flows visualized with graphite microparticles appear in the layer and droplets of a transparent liquid, the trajectory of the light spot on the layer and droplet surface is a two-dimensional trajectory in the form of an ellipse or a saddle. This indicates that the generation of the vortex flows in a liquid at vibrations is due to capillary oscillations in the orthogonally related directions. In the liquid layer and droplets on the surface of the flexible plate, the vibrations of which are generated by bending vibrations, the vortex flows appear due to the plate vibrations and the capillary oscillations of the surface of a layer or a droplet of the liquid. On the free surface of the liquid, the capillary waves, which are parametrically excited by the plate bending vibrations, are additionally modulated by the same bending vibrations in the transverse direction.

Numerical evaluation of gas core length in free surface vortices

NASA Astrophysics Data System (ADS)

Cristofano, L.; Nobili, M.; Caruso, G.

2014-11-01

The formation and evolution of free surface vortices represent an important topic in many hydraulic intakes, since strong whirlpools introduce swirl flow at the intake, and could cause entrainment of floating matters and gas. In particular, gas entrainment phenomena are an important safety issue for Sodium cooled Fast Reactors, because the introduction of gas bubbles within the core causes dangerous reactivity fluctuation. In this paper, a numerical evaluation of the gas core length in free surface vortices is presented, according to two different approaches. In the first one, a prediction method, developed by the Japanese researcher Sakai and his team, has been applied. This method is based on the Burgers vortex model, and it is able to estimate the gas core length of a free surface vortex starting from two parameters calculated with single-phase CFD simulations. The two parameters are the circulation and the downward velocity gradient. The other approach consists in performing a two-phase CFD simulation of a free surface vortex, in order to numerically reproduce the gas- liquid interface deformation. Mapped convergent mesh is used to reduce numerical error and a VOF (Volume Of Fluid) method was selected to track the gas-liquid interface. Two different turbulence models have been tested and analyzed. Experimental measurements of free surface vortices gas core length have been executed, using optical methods, and numerical results have been compared with experimental measurements. The computational domain and the boundary conditions of the CFD simulations were set consistently with the experimental test conditions.

Periodicity of the density wake past a vortex ring in a stratified liquid

NASA Astrophysics Data System (ADS)

Prokhorov, V.

2009-04-01

Spatial coherent structure of the density wake past a vortex ring moving horizontally in viscid stratified liquid is experimentally revealed. It follows from analysis that repetition period of the structure is determined by rotation radial frequency (or mean vorticity) of the vortex core and toward speed of the vortex ring. The wake formation of the ring is considered in respect to vorticity shedding which produces velocity disturbances in ambient medium. In case of stratified liquid velocity fluctuations, in their turn, cause density field distortion. This process is superimposed by vortex core oscillations, and, in result, vorticity shedding will be not monotonous but modulated at some frequency. So, the density wake is periodically structured, and the spatial period is defined by intrinsic frequency of the core and forward speed of the ring. To support analysis, experiments were conducted in which vortex rings excited by spring-piston generator were observed with high-sensitive Schlieren instrument and computer-controlled camera. Experimental tank was filled with salt-stratified water of constant buoyancy period, vortex ring velocities range from 3 to 16 cm/s. Spatial period is derived from schlieren image using two independent methods, both 2D spectral analysis and geometry calculations of the vortex core. Spatial periods and vortex intrinsic frequencies calculated by both algorithms are in good agreement; they vary in power lows depending on vortex speed

Variable-gravity anti-vortex and vapor-ingestion-suppression device

NASA Technical Reports Server (NTRS)

Grayson, Gary D. (Inventor)

2003-01-01

A liquid propellant management device for placement in a liquid storage tank adjacent an outlet of the storage tank to substantially reduce or eliminate the formation of a dip and vortex in the liquid of the tank, as well as prevent vapor ingestion into the outlet, as the liquid drains out through the outlet. The liquid propellant management device has a first member adapted to suppress the formation of a vortex of a liquid exiting the storage tank. A plate is affixed generally perpendicular to the first member, wherein the plate is adapted to suppress vapor ingestion into the outlet by reducing a dip in a surface level of the liquid leaving the tank. A second member is affixed to the second side of the plate. The second member ensures that the plate is wet with liquid and assists in positioning bubbles away from the outlet.

Significant and stable drag reduction with air rings confined by alternated superhydrophobic and hydrophilic strips

PubMed Central

Hu, Haibao; Wen, Jun; Bao, Luyao; Jia, Laibing; Song, Dong; Song, Baowei; Pan, Guang; Scaraggi, Michele; Dini, Daniele; Xue, Qunji; Zhou, Feng

2017-01-01

Superhydrophobic surfaces have the potential to reduce the viscous drag of liquids by significantly decreasing friction at a solid-liquid interface due to the formation of air layers between solid walls and interacting liquids. However, the trapped air usually becomes unstable due to the finite nature of the domain over which it forms. We demonstrate for the first time that a large surface energy barrier can be formed to strongly pin the three-phase contact line of air/water/solid by covering the inner rotor of a Taylor-Couette flow apparatus with alternating superhydrophobic and hydrophilic circumferential strips. This prevents the disruption of the air layer, which forms stable and continuous air rings. The drag reduction measured at the inner rotor could be as much as 77.2%. Moreover, the air layers not only significantly reduce the strength of Taylor vortexes but also influence the number and position of the Taylor vortex pairs. This has strong implications in terms of energy efficiency maximization for marine applications and reduction of drag losses in, for example, fluid transport in pipelines and carriers. PMID:28879234

Vortex tube can increase liquid hydrocarbon recovery at plant inlet

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

Hajdik, B.; Lorey, M.; Steinle, J.

1997-09-08

Use of a vortex-tube device yields improved inlet gas-liquid separation, when compared with a Joule-Thomson system, but is less costly and complex than a true isentropic system, such as a turboexpander. Because the vortex-tube unit provides separation as well as pressure reduction, the capital cost of a Joule-Thomson system with valve and separator will be similar to that of the vortex-tube system. Future applications of vortex-tube units will be concentrated where performance improvements over Joule-Thomson units, at low capital cost, are required. The operating characteristics of a vortex tube permit gas, in part, to be reduced in temperature to lessmore » than that normally achievable through isenthalpic expansion. The following three examples show how vortex technology can be applied to achieve these aims.« less

Vortices and quasiparticles near the superconductor-insulator transition in thin films.

PubMed

Galitski, Victor M; Refael, G; Fisher, Matthew P A; Senthil, T

2005-08-12

We study the low temperature behavior of an amorphous superconducting film driven normal by a perpendicular magnetic-field (B). For this purpose we introduce a new two-fluid formulation consisting of fermionized field-induced vortices and electrically neutralized Bogoliubov quasiparticles (spinons) interacting via a long-ranged statistical interaction. This approach allows us to access a novel non-Fermi-liquid phase, which naturally interpolates between the low B superconductor and the high B normal metal. We discuss the properties of the resulting "vortex metal" phase.

Determination of ibuprofen enantiomers in breast milk using vortex-assisted matrix solid-phase dispersion and direct chiral liquid chromatography.

PubMed

León-González, M E; Rosales-Conrado, N

2017-09-08

A mixture of β-cyclodextrin (β-CD) and primary and secondary amine (PSA) sorbents was employed for the extraction and quantification of ibuprofen enantiomers from human breast milk, combining a vortex-assisted matrix solid-phase dispersion method (MSPD) and direct chiral liquid chromatography (CLC) with ultraviolet detection (UV). The MSPD sample preparation procedure was optimized focusing on both the type and amount of dispersion/sorption sorbents and the nature of the elution solvent, in order to obtain acceptable recoveries and avoiding enantiomer conversion. These MSPD parameters were optimized with the aid of an experimental design approach. Hence, a factorial design was used for identification of the main variables affecting the extraction process of ibuprofen enantiomers. Under optimum selected conditions, MSPD combined with direct CLC-UV was successfully applied for ibuprofen enantiomeric determination in breast milk at enantiomer levels between 0.15 and 6.0μgg -1 . The proposed analytical method also provided good repeatability, with relative standard deviations of 6.4% and 8.3% for the intra-day and inter-day precision, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Core structure and dynamics of non-Abelian vortices in a biaxial nematic spinor Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Borgh, Magnus O.; Ruostekoski, Janne

2016-05-01

We demonstrate that multiple interaction-dependent defect core structures as well as dynamics of non-Abelian vortices can be realized in the biaxial nematic (BN) phase of a spin-2 atomic Bose-Einstein condensate (BEC). An experimentally simple protocol may be used to break degeneracy with the uniaxial nematic phase. We show that a discrete spin-space symmetry in the core may be reflected in a breaking of its spatial symmetry. The discrete symmetry of the BN order parameter leads to non-commuting vortex charges. We numerically simulate reconnection of non-Abelian vortices, demonstrating formation of the obligatory rung vortex. In addition to atomic BECs, non-Abelian vortices are theorized in, e.g., liquid crystals and cosmic strings. Our results suggest the BN spin-2 BEC as a prime candidate for their realization. We acknowledge financial support from the EPSRC.

Using a plenoptic sensor to reconstruct vortex phase structures.

PubMed

Wu, Chensheng; Ko, Jonathan; Davis, Christopher C

2016-07-15

A branch point problem and its solution commonly involve recognizing and reconstructing a vortex phase structure around a singular point. In laser beam propagation through random media, the destructive phase contributions from various parts of a vortex phase structure will cause a dark area in the center of the beam's intensity profile. This null of intensity can, in turn, prevent the vortex phase structure from being recognized. In this Letter, we show how to use a plenoptic sensor to transform the light field of a vortex beam so that a simple and direct reconstruction algorithm can be applied to reveal the vortex phase structure. As a result, we show that the plenoptic sensor is effective in detecting branch points and can be used to reconstruct phase distortion in a beam in a wide sense.

Numerical study of gravity effects on phase separation in a swirl chamber.

PubMed

Hsiao, Chao-Tsung; Ma, Jingsen; Chahine, Georges L

2016-01-01

The effects of gravity on a phase separator are studied numerically using an Eulerian/Lagrangian two-phase flow approach. The separator utilizes high intensity swirl to separate bubbles from the liquid. The two-phase flow enters tangentially a cylindrical swirl chamber and rotate around the cylinder axis. On earth, as the bubbles are captured by the vortex formed inside the swirl chamber due to the centripetal force, they also experience the buoyancy force due to gravity. In a reduced or zero gravity environment buoyancy is reduced or inexistent and capture of the bubbles by the vortex is modified. The present numerical simulations enable study of the relative importance of the acceleration of gravity on the bubble capture by the swirl flow in the separator. In absence of gravity, the bubbles get stratified depending on their sizes, with the larger bubbles entering the core region earlier than the smaller ones. However, in presence of gravity, stratification is more complex as the two acceleration fields - due to gravity and to rotation - compete or combine during the bubble capture.

Ionic-liquid-based dispersive liquid-liquid microextraction combined with magnetic solid-phase extraction for the determination of aflatoxins B1 , B2 , G1 , and G2 in animal feeds by high-performance liquid chromatography with fluorescence detection.

PubMed

Zhao, Jiao; Zhu, Yan; Jiao, Yang; Ning, Jinyan; Yang, Yaling

2016-10-01

A novel two-step extraction technique combining ionic-liquid-based dispersive liquid-liquid microextraction with magnetic solid-phase extraction was developed for the preconcentration and separation of aflatoxins in animal feedstuffs before high-performance liquid chromatography coupled with fluorescence detection. In this work, ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate was used as the extractant in dispersive liquid-liquid microextraction, and hydrophobic pelargonic acid modified Fe 3 O 4 magnetic nanoparticles as an efficient adsorbent were applied to retrieve the aflatoxins-containing ionic liquid. Notably, the target of magnetic nanoparticles was the ionic liquid rather than the aflatoxins. Because of the rapid mass transfer associated with the dispersive liquid-liquid microextraction and magnetic solid phase steps, fast extraction could be achieved. The main parameters affecting the extraction recoveries of aflatoxins were investigated and optimized. Under the optimum conditions, vortexing at 2500 rpm for 1 min in the dispersive liquid-liquid microextraction and magnetic solid-phase extraction and then desorption by sonication for 2 min with acetonitrile as eluent. The recoveries were 90.3-103.7% with relative standard deviations of 3.2-6.4%. Good linearity was observed with correlation coefficients ranged from 0.9986 to 0.9995. The detection limits were 0.632, 0.087, 0.422 and 0.146 ng/mL for aflatoxins B 1 , B2, G1, and G2, respectively. The results were also compared with the pretreatment method carried out by conventional immunoaffinity columns. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dispersive admicelle solid-phase extraction based on sodium dodecyl sulfate coated Fe3 O4 nanoparticles for the selective adsorption of three alkaloids in Gegen-Qinlian oral liquid before high-performance liquid chromatography.

PubMed

Shi, Zhihong; Xu, Dan; Zhao, Xuan; Li, Xinghong; Shen, Huimin; Yang, Bing; Zhang, Hongyi

2017-12-01

A novel dispersive admicelle solid-phase extraction method based on sodium dodecyl sulfate-coated Fe 3 O 4 nanoparticles was developed for the selective adsorption of berberine, coptisine, and palmatine in Gegen-Qinlian oral liquid before high-performance liquid chromatography. Fe 3 O 4 nanoparticles were synthesized by a chemical coprecipitation method and characterized by using transmission electron microscopy. Under acidic conditions, the surface of Fe 3 O 4 nanoparticles was coated with sodium dodecyl sulfate to form a nano-sized admicelle magnetic sorbent. Owing to electrostatic interaction, the alkaloids were adsorbed onto the oppositely charged admicelle magnetic nanoparticles. The quick separation of the analyte-adsorbed nanoparticles from the sample solution was performed by using Nd-Fe-B magnet. Best extraction efficiency was achieved under the following conditions: 800 μL Fe 3 O 4 nanoparticles suspension (20 mg/mL), 150 μL sodium dodecyl sulfate solution (10 mg/mL), pH 2, and vortexing time 2 min for the extraction of alkaloids from 10 mL of diluted sample. Four hundred microliters of methanol was used to desorb the alkaloids by vortexing for 1 min. Satisfactory extraction recoveries were obtained in the range of 85.9-120.3%, relative standard deviations for intra- and interday precisions were less than 6.3 and 10.0%, respectively. Finally, the established method was successfully applied to analyze the alkaloids in two batches of Gegen-Qinlian oral liquids. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bubbling and foaming assisted clearing of mucin plugs in microfluidic Y-junctions.

PubMed

Abdula, Daner; Lerud, Ryan; Rananavare, Shankar

2017-11-07

Microfluidic Y-junctions were used to study mechanical mechanisms involved in pig gastric mucin (PGM) plug removal from within one of two bifurcation branches with 2-phase air and liquid flow. Water control experiments showed moderate plug removal due to shear from vortex formation in the blockage branch and suggest a PGM yield stress of 35Pa, as determined by computational fluid dynamics. Addition of hexadecyltrimethylammonium bromide (CTAB) surfactant improved clearing effectiveness due to bubbling in 1mm diameter channels and foaming in 500μm diameter channels. Plug removal mechanisms have been identified as vortex shear, bubble scouring, and then foam scouring as air flow rate is increased with constant liquid flow. The onset of bubbling and foaming is attributed to a flow regime transition from slug to slug-annular. Flow rates explored for 1mm channels are typically experienced by bronchioles in generations 8 and 9 of lungs. Results have implications on treatment of cystic fibrosis and other lung diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Vortex phase-induced changes of the statistical properties of a partially coherent radially polarized beam.

PubMed

Guo, Lina; Chen, Yahong; Liu, Xianlong; Liu, Lin; Cai, Yangjian

2016-06-27

Partially coherent radially polarized (PCRP) beam was introduced and generated in recent years. In this paper, we investigate the statistical properties of a PCRP beam embedded with a vortex phase (i.e., PCRP vortex beam). We derive the analytical formula for the cross-spectral density matrix of a PCRP vortex beam propagating through a paraxial ABCD optical system and analyze the statistical properties of a PCRP vortex beam focused by a thin lens. It is found that the statistical properties of a PCRP vortex beam on propagation are much different from those of a PCRP beam. The vortex phase induces not only the rotation of the beam spot, but also the changes of the beam shape, the degree of polarization and the state of polarization. We also find that the vortex phase plays a role of resisting the coherence-induced degradation of the intensity distribution and the coherence-induced depolarization. Furthermore, we report experimental generation of a PCRP vortex beam for the first time. Our results will be useful for trapping and rotating particles, free-space optical communications and detection of phase object.

Universal lower limit on vortex creep in superconductors

DOE PAGES

Eley, Serena Merteen; Miura, Masashi; Maiorov, Boris Alfredo; ...

2017-02-13

Superconductors are excellent testbeds for studying vortices, topological excitations that also appear in superfluids, liquid crystals and Bose–Einstein condensates. Vortex motion can be disruptive; it can cause phase transitions, glitches in pulsars, and losses in superconducting microwave circuits, and it limits the current-carrying capacity of superconductors4. Understanding vortex dynamics is fundamentally and technologically important, and the competition between thermal energy and energy barriers defined by material disorder is not completely understood. Specifically, early measurements of thermally activated vortex motion (creep) in iron-based superconductors unveiled fast rates (S) comparable to measurements of YBa 2Cu 3O 7–δ. This was puzzling because Smore » is thought to somehow correlate with the Ginzburg number (Gi), and Gi is significantly lower in most iron-based superconductors than in YBa 2Cu 3O 7–δ. Here, we report very slow creep in BaFe 2(As 0.67P 0.33) 2 films, and propose the existence of a universal minimum realizable S ~ Gi 1/2(T/T c) (T c is the superconducting transition temperature) that has been achieved in our films and few other materials, and is violated by none. Furthermore, this limitation provides new clues about designing materials with slow creep and the interplay between material parameters and vortex dynamics.« less

Universal lower limit on vortex creep in superconductors

NASA Astrophysics Data System (ADS)

Eley, S.; Miura, M.; Maiorov, B.; Civale, L.

2017-04-01

Superconductors are excellent testbeds for studying vortices, topological excitations that also appear in superfluids, liquid crystals and Bose-Einstein condensates. Vortex motion can be disruptive; it can cause phase transitions, glitches in pulsars, and losses in superconducting microwave circuits, and it limits the current-carrying capacity of superconductors. Understanding vortex dynamics is fundamentally and technologically important, and the competition between thermal energy and energy barriers defined by material disorder is not completely understood. Specifically, early measurements of thermally activated vortex motion (creep) in iron-based superconductors unveiled fast rates (S) comparable to measurements of YBa 2Cu3O7-δ (refs ,,,,,). This was puzzling because S is thought to somehow correlate with the Ginzburg number (Gi), and Gi is significantly lower in most iron-based superconductors than in YBa 2Cu3O7-δ. Here, we report very slow creep in BaFe 2(As0.67P0.33)2 films, and propose the existence of a universal minimum realizable S ~ Gi1/2(T/Tc) (Tc is the superconducting transition temperature) that has been achieved in our films and few other materials, and is violated by none. This limitation provides new clues about designing materials with slow creep and the interplay between material parameters and vortex dynamics.

Generation of singular optical beams from fundamental Gaussian beam using Sagnac interferometer

NASA Astrophysics Data System (ADS)

Naik, Dinesh N.; Viswanathan, Nirmal K.

2016-09-01

We propose a simple free-space optics recipe for the controlled generation of optical vortex beams with a vortex dipole or a single charge vortex, using an inherently stable Sagnac interferometer. We investigate the role played by the amplitude and phase differences in generating higher-order Gaussian beams from the fundamental Gaussian mode. Our simulation results reveal how important the control of both the amplitude and the phase difference between superposing beams is to achieving optical vortex beams. The creation of a vortex dipole from null interference is unveiled through the introduction of a lateral shear and a radial phase difference between two out-of-phase Gaussian beams. A stable and high quality optical vortex beam, equivalent to the first-order Laguerre-Gaussian beam, is synthesized by coupling lateral shear with linear phase difference, introduced orthogonal to the shear between two out-of-phase Gaussian beams.

Structure of vortices in superfluid 3He A-like phase in uniaxially stretched aerogel

NASA Astrophysics Data System (ADS)

Aoyama, Kazushi; Ikeda, Ryusuke

2009-02-01

Possible vortex-core transitions in A-like phase of superfluid 3He in uniaxially stretched aerogel are investigated. Since the global anisotropy in this system induces the polar pairing state in a narrow range close to the superfluid transition in addition to the A-like and B-like phases, the polar state may occur in the core of a vortex in the A-like phase identified with the ABM pairing state, like in the case of the bulk B phase where a core including the ABM state is realized at higher pressures. We examine the core structure of a single vortex under the boundary condition compatible with the Mermin-Ho vortex in the presence of the dipole interaction. Following Salomaa and Volovik's approach, we numerically solve the Ginzburg-Landau equation for an axially symmetric vortex and, by examining its stability against nonaxisymmetric perturbations, discuss possible vortex core states. It is found that a first order transition on core states may occur on warming from an axisymmetric vortex with a nonunitary core to a singular vortex with the polar core.

High-charge and multiple-star vortex coronagraphy from stacked vector vortex phase masks.

PubMed

Aleksanyan, Artur; Brasselet, Etienne

2018-02-01

Optical vortex phase masks are now installed at many ground-based large telescopes for high-contrast astronomical imaging. To date, such instrumental advances have been restricted to the use of helical phase masks of the lowest even order, while future giant telescopes will require high-order masks. Here we propose a single-stage on-axis scheme to create high-order vortex coronagraphs based on second-order vortex phase masks. By extending our approach to an off-axis design, we also explore the implementation of multiple-star vortex coronagraphy. An experimental laboratory demonstration is reported and supported by numerical simulations. These results offer a practical roadmap to the development of future coronagraphic tools with enhanced performances.

Rapid determination of hydrophilic phenols in olive oil by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and screen-printed carbon electrodes.

PubMed

Fernández, Elena; Vidal, Lorena; Canals, Antonio

2018-05-01

A novel approach is presented to determine hydrophilic phenols in olive oil samples, employing vortex-assisted reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for sample preparation and screen-printed carbon electrodes for voltammetric analysis. The oxidation of oleuropein, hydroxytyrosol, caffeic acid, ferulic acid and tyrosol was investigated, being caffeic acid and tyrosol selected for quantification. A matrix-matching calibration using sunflower oil as analyte-free sample diluted with hexane was employed to compensate matrix effects. Samples were analyzed under optimized RP-DLLME conditions, i.e., extractant phase, 1M HCl; extractant volume, 100µL; extraction time, 2min; centrifugation time, 10min; centrifugation speed, 4000rpm. The working range showed a good linearity between 0.075 and 2.5mgL -1 (r = 0.998, N = 7) for caffeic acid, and between 0.075 and 3mgL -1 (r = 0.999, N = 8) for tyrosol. The methodological limit of detection was empirically established at 0.022mgL -1 for both analytes, which is significantly lower than average contents found in olive oil samples. The repeatability was evaluated at two different spiking levels (i.e., 0.5mgL -1 and 2mgL -1 ) and coefficients of variation ranged from 8% to 11% (n = 5). The applicability of the proposed method was tested in olive oil samples of different quality (i.e., refined olive oil, virgin olive oil and extra virgin olive oil). Relative recoveries varied between 83% and 108% showing negligible matrix effects. Finally, fifteen samples were analyzed by the proposed method and a high correlation with the traditional Folin-Ciocalteu spectrophotometric method was obtained. Thereafter, the concentrations of the fifteen oil samples were employed as input variables in linear discriminant analysis in order to distinguish between olive oils of different quality. Copyright © 2017 Elsevier B.V. All rights reserved.

Absence of Cyclotron Resonance in the Anomalous Metallic Phase in InOx

NASA Astrophysics Data System (ADS)

Wang, Youcheng; Tamir, I.; Shahar, D.; Armitage, N. P.

2018-04-01

It is observed that many thin superconducting films with not too high disorder level (generally RN/□<2000 Ω ) placed in magnetic field show an anomalous metallic phase where the resistance is low but still finite as temperature goes to zero. Here we report in weakly disordered amorphous InOx thin films that this anomalous metal phase possesses no cyclotron resonance and hence non-Drude electrodynamics. The absence of a finite frequency resonant mode can be associated with a vanishing downstream component of the vortex current parallel to the supercurrent and an emergent particle-hole symmetry of this metal, which establishes its non-Fermi-liquid character.

Application of Optimized Vortex-Assisted Surfactant-Enhanced DLLME for Preconcentration of Thymol and Carvacrol, and Their Determination by HPLC-UV: Response Surface Methodology.

PubMed

Ghaedi, Mehrorang; Roosta, Mostafa; Khodadoust, Saeid; Daneshfar, Ali

2015-08-01

A novel vortex-assisted surfactant-enhanced dispersive liquid-liquid microextraction combined with high-performance liquid chromatography (VASEDLLME-HPLC) was developed for the determination of thymol and carvacrol (phenolic compound). In this method, the extraction solvent (CHCl3) was dispersed into the aqueous samples via a vortex agitator and addition of the surfactant (Triton X-100). The preliminary experiments were undertaken to select the best extraction solvent and surfactant. The influences of effective variables were investigated using a Plackett-Burman 2(7-4) screening design and then, the significant variables were optimized by using a central composite design combined with desirability function. Working under optimum conditions specified as: 140 µL CHCl3, 0.08% (w/v, Triton X-100), 3 min extraction time, 6 min centrifugation at 4,500 rpm, pH 7, 0.0% (w/v) NaCl permit achievement of high and reasonable linear range over 0.005-4.0 mg L(-1) with R(2) = 0.9998 (n = 10). The separation of thymol and carvacrol was achieved in <14 min using a C18 column and an isocratic binary mobile phase acetonitrile-water (55:45, v/v) with a flow rate of 1.0 mL min(-1). The VASEDLLME is applied for successful determination of carvacrol and thymol in different thyme and pharmaceutical samples with relative standard deviation <4.7% (n = 5). © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Application of dispersive liquid-liquid microextraction coupled with vortex-assisted hydrophobic magnetic nanoparticles based solid-phase extraction for determination of aflatoxin M1 in milk samples by sensitive micelle enhanced spectrofluorimetry.

PubMed

Amoli-Diva, Mitra; Taherimaslak, Zohreh; Allahyari, Mehdi; Pourghazi, Kamyar; Manafi, Mohammad Hanif

2015-03-01

An efficient, simple and fast low-density solvent based dispersive liquid-liquid microextraction (LDS-DLLME) followed by vortex-assisted dispersive solid phase extraction (VA-D-SPE) has been developed as a new approach for extraction and preconcentration of aflatoxin M1 in milk samples prior to its micelle enhanced spectrofluorimetic determination. In this LDS-DLLME coupled VA-D-SPE method, milk samples were first treated with methanol/water (80:20, v/v) after removing the fat layer. This solvent was directly used as the dispersing solvent in DLLME along with using 1-heptanol (as a low-density solvent with respect to water) as the extracting solvent. In VA-D-SPE approach, hydrophobic oleic acid modified Fe3O4 nanoparticles were used to retrieve the analyte from the DLLME step. It is considerably that the target of VA-D-SPE was 1-heptanol rather than the aflatoxin M1 directly. The main parameters affecting the efficiency of LDS-DLLME and VA-D-SPE procedures and signal enhancement of aflatoxin M1 were investigated and optimized. Under the optimum conditions, the method was linear in the range from 0.02 to 200 µg L(-1) with the correlation coefficient (R(2)) of 0.9989 and detection limit of 13 ng L(-1). The intra-day precision was 2.9 and 4.3% and the inter-day precision was 2.1 and 3.3% for concentration of 2 and 50 µg L(-1) respectively. The developed method was applied for extraction and preconcentration of AFM1 in three commercially available milk samples and the results were compared with the official AOAC method. Copyright © 2014 Elsevier B.V. All rights reserved.

Motion of vortices in inhomogeneous Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Groszek, Andrew J.; Paganin, David M.; Helmerson, Kristian; Simula, Tapio P.

2018-02-01

We derive a general and exact equation of motion for a quantized vortex in an inhomogeneous two-dimensional Bose-Einstein condensate. This equation expresses the velocity of a vortex as a sum of local ambient density and phase gradients in the vicinity of the vortex. We perform Gross-Pitaevskii simulations of single-vortex dynamics in both harmonic and hard-walled disk-shaped traps, and find excellent agreement in both cases with our analytical prediction. The simulations reveal that, in a harmonic trap, the main contribution to the vortex velocity is an induced ambient phase gradient, a finding that contradicts the commonly quoted result that the local density gradient is the only relevant effect in this scenario. We use our analytical vortex velocity formula to derive a point-vortex model that accounts for both density and phase contributions to the vortex velocity, suitable for use in inhomogeneous condensates. Although good agreement is obtained between Gross-Pitaevskii and point-vortex simulations for specific few-vortex configurations, the effects of nonuniform condensate density are in general highly nontrivial, and are thus difficult to efficiently and accurately model using a simplified point-vortex description.

Enhanced spectrophotometric detection of Hg in water samples by surface plasmon resonance of Au nanoparticles after preconcentration with vortex-assisted liquid-liquid microextraction

NASA Astrophysics Data System (ADS)

Martinis, Estefanía M.; Wuilloud, Rodolfo G.

2016-10-01

This article presents an efficient, simple, and cost-effective method for the determination of trace amounts of Hg by vortex-assisted liquid-liquid microextraction (VALLME) coupled to microvolume UV-Vis spectrophotometry. This method correlates changes in the intensity of localized surface plasmon resonance (LSPR) of tetraoctylammonium bromide (TOABr) coated Au nanoparticles (NPs) after interaction with Hg2+ ion. Spectroscopic measurements of the TOABr-coated Au NPs phase with particular absorption properties (strong and well-defined absorption bands) after analyte extraction by VALLME, provide an accurate and sensitive determination of Hg in water samples, comparable with measurements obtained by atomic absorption spectrometry (AAS). Different variables including sample volume, extraction time, and TOABr-coated Au NPs dispersion volume were carefully studied; final experimental conditions were 5 mL, 120 μL and 5 min respectively. The limit of detection (LOD) was 0.8 ng mL- 1. The calibration curve was linear at concentrations between the limit of quantification (LOQ) (4.9 ng mL- 1) and up to at least 120 ng mL- 1 of Hg. The relative standard deviation for six replicate determinations of 20 ng mL- 1 of Hg was 4.7%. This method exhibited an excellent analytical performance in terms of selectivity and sensitivity and it was finally applied for Hg determination in spiked tap and mineral water samples.

Generation of helical Ince-Gaussian beams: beam-shaping with a liquid crystal display

NASA Astrophysics Data System (ADS)

Davis, Jeffrey A.; Bentley, Joel B.; Bandres, Miguel A.; Gutiérrez-Vega, Julio C.

2006-08-01

We review the three types of laser beams - Hermite-Gaussian (HG), Laguerre-Gaussian (LG) and the newly discovered Ince-Gaussian (IG) beams. We discuss the helical forms of the LG and IG beams that consist of linear combinations of the even and odd solutions and form a number of vortices that are useful for optical trapping applications. We discuss how to generate these beams by encoding the desired amplitude and phase onto a single parallel-aligned liquid crystal display (LCD). We introduce a novel interference technique where we generate both the object and reference beams using a single LCD and show the vortex interference patterns.

A simple and sensitive vortex-assisted ionic liquid-dispersive microextraction and spectrophotometric determination of selenium in food samples.

PubMed

Bağda, Esra; Tüzen, Mustafa

2017-10-01

In the present study, a novel and eco-friendly vortex-assisted ionic liquid-based microextraction method was developed for the determination of selenium in food. The microextraction method is based on the liberation of iodine in the presence of selenium; the liberated iodine reacts with I - to form I 3 - . Anionic I 3 - reacts with cationic crystal violet dye, and the product is extracted into 1-hexyl-3-methylimidazolium hexafluorophosphate phase in the presence of Triton X-114. The proposed method is linear in the range of 2.0-70µgL -1 and has a detection limit of 9.8×10 -2 µgL -1 . Relative standard deviations were 3.67% and 2.89% for the five replicate measurements of 14 and 35µgL -1 Se(IV), respectively. The proposed method was successfully applied to different food samples (NIST SRM 2976 mussel tissue, pepper, ginger, wheat flour, red lentil, traditional soup, cornflour, cornstarch, and garlic) after microwave digestion. Copyright © 2017 Elsevier Ltd. All rights reserved.

Magnification of signatures of a topological phase transition by quantum zero point motion

NASA Astrophysics Data System (ADS)

Lopes, Pedro L. e. S.; Ghaemi, Pouyan

2015-08-01

We show that the zero point motion of a vortex in superconducting doped topological insulators leads to significant changes in the electronic spectrum at the topological phase transition in this system. This topological phase transition is tuned by the doping level, and the corresponding effects are manifest in the density of states at energies which are on the order of the vortex fluctuation frequency. Although the electronic energy gap in the spectrum generated by a stationary vortex is but a small fraction of the bulk superconducting gap, the vortex fluctuation frequency may be much larger. As a result, this quantum zero point motion can induce a discontinuous change in the spectral features of the system at the topological vortex phase transition to energies which are well within the resolution of scanning tunneling microscopy. This discontinuous change is exclusive to superconducting systems in which we have a topological phase transition. Moreover, the phenomena studied in this paper present effects of Magnus forces on the vortex spectrum which are not present in the ordinary s -wave superconductors. Finally, we demonstrate explicitly that the vortex in this system is equivalent to a Kitaev chain. This allows for the mapping of the vortex fluctuating scenario in three dimensions into similar one-dimensional situations in which one may search for other novel signatures of topological phase transitions.

Vortex-liquid{endash}vortex-crystal transition in type-II superconductors

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

Newman, T.J.; Moore, M.A.

1996-09-01

We present in detail a functional renormalization group (FRG) study of a Landau-Ginzburg model of type-II superconductors (generalized to {ital N}/2 complex fields) in an external magnetic field, both for a pure system and also in the presence of quenched random impurities. If the coupling functions are restricted to the space of functions with nonzero support only at reciprocal lattice vectors corresponding to the Abrikosov lattice, we find a stable FRG fixed point in the presence of disorder for 1{lt}{ital N}{lt}4, identical to that of the disordered {ital O}({ital N}) model in {ital d}{minus}2 dimensions. This implies a continuous transitionmore » from the vortex crystal to vortex liquid in the presence of disorder, but only for {ital d}{gt}4. The nonzero-temperature transition will disappear in physical dimensions. The pure system has a stable fixed point only for {ital N}{gt}4. Therefore the physical case ({ital N}=2) is likely to have a first-order transition in the absence of quenched disorder. We give a full discussion of both the motivation of the model and the details of the FRG calculation. We also place our results in context with regard to the current experimental scene concerning the high-{ital T}{sub {ital c}} compounds. In particular, we discuss the relevance of our results to the recently discovered critical end point in the phase diagram of Bi-Sr-Ca-Cu-O. The main results of this analysis were previously reported in the form of a Letter [M.A. Moore and T.J. Newman, Phys. Rev. Lett. {bold 75}, 533 (1995)]. {copyright} {ital 1996 The American Physical Society.}« less

Preconcentration of Trace Neonicotinoid Insecticide Residues Using Vortex-Assisted Dispersive Micro Solid-Phase Extraction with Montmorillonite as an Efficient Sorbent.

PubMed

Moyakao, Khwankaew; Santaladchaiyakit, Yanawath; Srijaranai, Supalax; Vichapong, Jitlada

2018-04-11

In this work, we investigated montmorillonite for adsorption of neonicotinoid insecticides in vortex-assisted dispersive micro-solid phase extraction (VA-d-μ-SPE). High-performance liquid chromatography with photodiode array detection was used for quantification and determination of neonicotinoid insecticide residues, including thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid. In this method, the solid sorbent was dispersed into the aqueous sample solution and vortex agitation was performed to accelerate the extraction process. Finally, the solution was filtered from the solid sorbent with a membrane filter. The parameters affecting the extraction efficiency of the proposed method were optimized, such as amount of sorbent, sample volume, salt addition, type and volume of extraction solvent, and vortex time. The adsorbing results show that montmorillonite could be reused at least 4 times and be used as an effective adsorbent for rapid extraction/preconcentration of neonicotinoid insecticide residues. Under optimum conditions, linear dynamic ranges were achieved between 0.5 and 1000 ng mL -1 with a correlation of determination ( R² ) greater than 0.99. Limit of detection (LOD) ranged from 0.005 to 0.065 ng mL -1 , while limit of quantification (LOQ) ranged from 0.008 to 0.263 ng mL -1 . The enrichment factor (EF) ranged from 8 to 176-fold. The results demonstrated that the proposed method not only provided a more simple and sensitive method, but also can be used as a powerful alternative method for the simultaneous determination of insecticide residues in natural surface water and fruit juice samples.

Rapid pretreatment and determination of bisphenol A in water samples based on vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography with fluorescence detection.

PubMed

Yang, Xiao; Diao, Chun-Peng; Sun, Ai-Ling; Liu, Ren-Min

2014-10-01

A method for the rapid pretreatment and determination of bisphenol A in water samples based on vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography with fluorescence detection was proposed in this paper. A simple apparatus consisting of a test tube and a cut-glass dropper was designed and applied to collect the floating extraction drop in liquid-liquid microextraction when low-density organic solvent was used as the extraction solvent. Solidification and melting steps that were tedious but necessary once the low-density organic solvent used as extraction solvent could be avoided by using this apparatus. Bisphenol A was selected as model pollutant and vortex-assisted liquid-liquid microextraction was employed to investigate the usefulness of the apparatus. High-performance liquid chromatography with fluorescence detection was selected as the analytical tool for the detection of bisphenol A. The linear dynamic range was from 0.10 to 100 μg/L for bisphenol A, with good squared regression coefficient (r(2) = 0.9990). The relative standard deviation (n = 7) was 4.7% and the limit of detection was 0.02 μg/L. The proposed method had been applied to the determination of bisphenol A in natural water samples and was shown to be economical, fast, and convenient. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Persistence of metastable vortex lattice domains in MgB2 in the presence of vortex motion.

PubMed

Rastovski, C; Schlesinger, K J; Gannon, W J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

2013-09-06

Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

Broadband and high-efficiency vortex beam generator based on a hybrid helix array.

PubMed

Fang, Chaoqun; Wu, Chao; Gong, Zhijie; Zhao, Song; Sun, Anqi; Wei, Zeyong; Li, Hongqiang

2018-04-01

The vortex beam which carries the orbital angular momentum has versatile applications, such as high-resolution imaging, optical communications, and particle manipulation. Generating vortex beams with the Pancharatnam-Berry (PB) phase has drawn considerable attention for its unique spin-to-orbital conversion features. Despite the PB phase being frequency independent, an optical element with broadband high-efficiency circular polarization conversion feature is still needed for the broadband high-efficiency vortex beam generation. In this work, a broadband and high-efficiency vortex beam generator based on the PB phase is built with a hybrid helix array. Such devices can generate vortex beams with arbitrary topological charge. Moreover, vortex beams with opposite topological charge can be generated with an opposite handedness incident beam that propagates backward. The measured efficiency of our device is above 65% for a wide frequency range, with the relative bandwidth of 46.5%.

Generation of shockwave and vortex structures at the outflow of a boiling water jet

NASA Astrophysics Data System (ADS)

Alekseev, M. V.; Lezhnin, S. I.; Pribaturin, N. A.; Sorokin, A. L.

2014-12-01

Results of numerical simulation for shock waves and generation of vortex structures during unsteady outflow of boiling liquid jet are presented. The features of evolution of shock waves and vortex structures formation during unsteady outflow of boiling water are compared with corresponding structures during unsteady gas outflow.

A Bragg glass phase in the vortex lattice of a type II superconductor.

PubMed

Klein, T; Joumard, I; Blanchard, S; Marcus, J; Cubitt, R; Giamarchi, T; Le Doussal, P

2001-09-27

Although crystals are usually quite stable, they are sensitive to a disordered environment: even an infinitesimal amount of impurities can lead to the destruction of crystalline order. The resulting state of matter has been a long-standing puzzle. Until recently it was believed to be an amorphous state in which the crystal would break into 'crystallites'. But a different theory predicts the existence of a novel phase of matter: the so-called Bragg glass, which is a glass and yet nearly as ordered as a perfect crystal. The 'lattice' of vortices that contain magnetic flux in type II superconductors provide a good system to investigate these ideas. Here we show that neutron-diffraction data of the vortex lattice provides unambiguous evidence for a weak, power-law decay of the crystalline order characteristic of a Bragg glass. The theory also predicts accurately the electrical transport properties of superconductors; it naturally explains the observed phase transitions and the dramatic jumps in the critical current associated with the melting of the Bragg glass. Moreover, the model explains experiments as diverse as X-ray scattering in disordered liquid crystals and the conductivity of electronic crystals.

Evaluation of Impinging Stream Vortex Chamber Concepts for Liquid Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Trinh, Huu P.; Bullard, Brad; Kopicz, Charles; Michaels, Scott; Turner, James (Technical Monitor)

2001-01-01

To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for liquid rocket engine applications. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concepts not only offer the system simplicity, but they also would enhance the combustion performance. The test results showed that the chamber performance was markedly high even at a low chamber length-to-diameter ratio (L/D). This incentive can be translated to a convenience in the thrust chamber packaging. Variations of the vortex chamber concepts have been introduced in the past few decades. These investigations include an ongoing work at Orbital Technologies Corporation (ORBITEC). By injecting the oxidizer tangentially at the chamber convergence and fuel axially at the chamber head end, Knuth et al. were able to keep the wall relatively cold. A recent investigation of the low L/D vortex chamber concept for gel propellants was conducted by Michaels. He used both triplet (two oxidizer and one fuel orifices) and unlike impinging schemes to inject propellants tangentially along the chamber wall. Michaels called the subject injection scheme as Impinging Stream Vortex Chamber (ISVC). His preliminary tests showed that high performance, with an Isp efficiency of 92%, can be obtained. MSFC and the U.S. Army are jointly investigating an application of the ISVC concept for the cryogenic oxygen/hydrocarbon propellant system. This vortex chamber concept is currently tested with gel propellants at AMCOM at Redstone Arsenal, Alabama. A version of this concept for the liquid oxygen (LOX)/hydrocarbon fuel (RPM) system has been derived from the one for the gel propellant.

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

Eley, Serena Merteen; Miura, Masashi; Maiorov, Boris Alfredo

Superconductors are excellent testbeds for studying vortices, topological excitations that also appear in superfluids, liquid crystals and Bose–Einstein condensates. Vortex motion can be disruptive; it can cause phase transitions, glitches in pulsars, and losses in superconducting microwave circuits, and it limits the current-carrying capacity of superconductors4. Understanding vortex dynamics is fundamentally and technologically important, and the competition between thermal energy and energy barriers defined by material disorder is not completely understood. Specifically, early measurements of thermally activated vortex motion (creep) in iron-based superconductors unveiled fast rates (S) comparable to measurements of YBa 2Cu 3O 7–δ. This was puzzling because Smore » is thought to somehow correlate with the Ginzburg number (Gi), and Gi is significantly lower in most iron-based superconductors than in YBa 2Cu 3O 7–δ. Here, we report very slow creep in BaFe 2(As 0.67P 0.33) 2 films, and propose the existence of a universal minimum realizable S ~ Gi 1/2(T/T c) (T c is the superconducting transition temperature) that has been achieved in our films and few other materials, and is violated by none. Furthermore, this limitation provides new clues about designing materials with slow creep and the interplay between material parameters and vortex dynamics.« less

Water-contained surfactant-based vortex-assisted microextraction method combined with liquid chromatography for determination of synthetic antioxidants from edible oil.

PubMed

Amlashi, Nadiya Ekbatani; Hadjmohammadi, Mohammad Reza; Nazari, Seyed Saman Seyed Jafar

2014-09-26

For the first time, a novel water-contained surfactant-based vortex-assisted microextraction method (WSVAME) was developed for the extraction of two synthetic antioxidants (t-butyl hydroquinone (TBHQ) and butylated hydroxyanisole (BHA)) from edible oil samples. The novel microextraction method is based on the injection of an aqueous solution of non-ionic surfactant, Brij-35, into the oil sample in a conical bottom glass tube to form a cloudy solution. Vortex mixing was applied to accelerate the dispersion process. After extraction and phase separation by centrifugation, the lower sediment phase was directly analyzed by HPLC. The effects of the four experimental parameters including volume and concentration of extraction solvent (aqueous solution of Brij-35), percentage of acetic acid added to the oil sample and vortex time on the extraction efficiency were studied with a full factorial design. The central composite design and multiple linear regression method were applied for the construction of the best polynomial model based on experimental recoveries. The proposed method showed good linearity within the range of 0.200-200 μg mL(-1), the square of correlation coefficient higher than 0.999 and appropriate limit of detection (0.026 and 0.020 μg mL(-1) for TBHQ and BHA, respectively), while the precision for inner-day was ≤ 3.0 (n=5) and it was ≤ 3.80 (n=5) for inter-day assay. Under the optimal condition (30 μL of 0.10 mol L(-1) Brij-35 solution as extraction solvent and vortex time 1 min), the method was successfully applied for determination of TBHQ and BHA in different commercial edible oil samples. The recoveries in all cases were above 95%, with relative standard deviations below 5%. This approach is considered as a simple, sensitive and environmentally friendly method because of biodegradability of the extraction phase and no use of organic solvent in the extraction procedure. Copyright © 2014 Elsevier B.V. All rights reserved.

Vortex rings in Bose gas

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

Belyaev, S. T., E-mail: bst@kiae.ru

2016-06-15

We consider excitations that exist, in addition to phonons, in the ideal Bose gas at zero temperature. These excitations are vortex rings whose energy spectrum is similar to the roton one in liquid helium.

Evolution of phase singularities of vortex beams propagating in atmospheric turbulence.

PubMed

Ge, Xiao-Lu; Wang, Ben-Yi; Guo, Cheng-Shan

2015-05-01

Optical vortex beams propagating through atmospheric turbulence are studied by numerical modeling, and the phase singularities of the vortices existing in the turbulence-distorted beams are calculated. It is found that the algebraic sum of topological charges (TCs) of all the phase singularities existing in test aperture is approximately equal to the TC of the input vortex beam. This property provides us a possible approach for determining the TC of the vortex beam propagating through the atmospheric turbulence, which could have potential application in optical communication using optical vortices.

The influence of liquid-gas velocity ratio on the noise of the cooling tower

NASA Astrophysics Data System (ADS)

Yang, Bin; Liu, Xuanzuo; Chen, Chi; Zhao, Zhouli; Song, Jinchun

2018-05-01

The noise from the cooling tower has a great influence on psychological performance of human beings. The cooling tower noise mainly consists of fan noise, falling water noise and mechanical noise. This thesis used DES turbulence model with FH-W model to simulate the flow and sound pressure field in cooling tower based on CFD software FLUENT and analyzed the influence of different kinds noise, which affected by diverse factors, on the cooling tower noise. It can be concluded that the addition of cooling water can reduce the turbulence and vortex noise of the rotor fluid field in the cooling tower at some extent, but increase the impact noise of the liquid-gas two phase. In general, the cooling tower noise decreases with the velocity ratio of liquid to gas increasing, and reaches the lowest when the velocity ratio of liquid to gas is close to l.

Dual gauge field theory of quantum liquid crystals in three dimensions

NASA Astrophysics Data System (ADS)

Beekman, Aron J.; Nissinen, Jaakko; Wu, Kai; Zaanen, Jan

2017-10-01

The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emerge whenever translational symmetry is restored. We also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.

Antifouling booster biocide extraction from marine sediments: a fast and simple method based on vortex-assisted matrix solid-phase extraction.

PubMed

Caldas, Sergiane Souza; Soares, Bruno Meira; Abreu, Fiamma; Castro, Ítalo Braga; Fillmann, Gilberto; Primel, Ednei Gilberto

2018-03-01

This paper reports the development of an analytical method employing vortex-assisted matrix solid-phase dispersion (MSPD) for the extraction of diuron, Irgarol 1051, TCMTB (2-thiocyanomethylthiobenzothiazole), DCOIT (4,5-dichloro-2-n-octyl-3-(2H)-isothiazolin-3-one), and dichlofluanid from sediment samples. Separation and determination were performed by liquid chromatography tandem-mass spectrometry. Important MSPD parameters, such as sample mass, mass of C18, and type and volume of extraction solvent, were investigated by response surface methodology. Quantitative recoveries were obtained with 2.0 g of sediment sample, 0.25 g of C18 as the solid support, and 10 mL of methanol as the extraction solvent. The MSPD method was suitable for the extraction and determination of antifouling biocides in sediment samples, with recoveries between 61 and 103% and a relative standard deviation lower than 19%. Limits of quantification between 0.5 and 5 ng g -1 were obtained. Vortex-assisted MPSD was shown to be fast and easy to use, with the advantages of low cost and reduced solvent consumption compared to the commonly employed techniques for the extraction of booster biocides from sediment samples. Finally, the developed method was applied to real samples. Results revealed that the developed extraction method is effective and simple, thus allowing the determination of biocides in sediment samples.

Influence of columnar defects on the thermodynamic properties of BSCCO

NASA Astrophysics Data System (ADS)

van der Beek, C. J.; Indenbom, M. V.; Berseth, V.; Konczykowski, M.; Li, T. W.; Kes, P. H.; Benoit, W.

1996-03-01

Amorphous columnar defects strongly affect the reversible magnetization of Bi2Sr2CaCu2O8+δ single crystals both in the vortex solid, where the change reflects the change in vortex energy due to pinning, and in the vortex liquid, where the randomly positioned columns disrupt the interaction between superconducting fluctuations.

Vortex diode jet

DOEpatents

Houck, Edward D.

1994-01-01

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

Bragg-Berry mirrors: reflective broadband q-plates.

PubMed

Rafayelyan, Mushegh; Brasselet, Etienne

2016-09-01

We report on the experimental realization of flat mirrors enabling the broadband generation of optical vortices upon reflection. The effect is based on the geometric Berry phase associated with the circular Bragg reflection phenomenon from chiral uniaxial media. We show the reflective optical vortex generation from both diffractive and nondiffractive paraxial light beams using spatially patterned chiral liquid crystal films. The intrinsic spectrally broadband character of spin-orbit generation of optical phase singularities is demonstrated over the full visible domain. Our results do not rely on any birefringent retardation requirement and, consequently, foster the development of a novel generation of robust optical elements for spin-orbit photonic technologies.

Thermodynamic evidence for the Bose glass transition in twinned YBa 2 Cu 3 O 7 - δ crystals

DOE PAGES

Pérez-Morelo, D. J.; Osquiguil, E.; Kolton, A. B.; ...

2015-07-21

We used a micromechanical torsional o scillator to measure the magnetic response of a twinned YBaBa2Cu3O7-δ single crystal disk near the Bose glass transition. We observe an anomaly in the temperature dependence of the magnetization consistent with the appearance of a magnetic shielding perpendicular to the correlated pinning of the twin boundaries. This effect is related to the thermodynamic transition from the vortex liquid phase to a Bose glass state.

Simultaneous determination of seven phthalic acid esters in beverages using ultrasound and vortex-assisted dispersive liquid-liquid microextraction followed by high-performance liquid chromatography.

PubMed

Yılmaz, Pelin Köseoğlu; Ertaş, Abdulselam; Kolak, Ufuk

2014-08-01

A sensitive, rapid, and simple high-performance liquid chromatography with UV detection method was developed for the simultaneous determination of seven phthalic acid esters (dimethyl phthalate, dipropyl phthalate, di-n-butyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate, di-(2-ethylhexyl) phthalate, and di-n-octyl phthalate) in several kinds of beverage samples. Ultrasound and vortex-assisted dispersive liquid-liquid microextraction method was used. The separation was performed using an Intersil ODS-3 column (C18 , 250 × 4.6 mm, 5.0 μm) and a gradient elution with a mobile phase consisting of MeOH/ACN (50:50) and 0.2 M KH2 PO4 buffer. Analytes were detected by a UV detector at 230 nm. The developed method was validated in terms of linearity, limit of detection, limit of quantification, repeatability, accuracy, and recovery. Calibration equations and correlation coefficients (> 0.99) were calculated by least squares method with weighting factor. The limit of detection and quantification were in the range of 0.019-0.208 and 0.072-0.483 μg/L. The repeatability and intermediate precision were determined in terms of relative standard deviation to be within 0.03-3.93 and 0.02-4.74%, respectively. The accuracy was found to be in the range of -14.55 to 15.57% in terms of relative error. Seventeen different beverage samples in plastic bottles were successfully analyzed, and ten of them were found to be contaminated by different phthalic acid esters. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alternative solvent-based methyl benzoate vortex-assisted dispersive liquid-liquid microextraction for the high-performance liquid chromatographic determination of benzimidazole fungicides in environmental water samples.

PubMed

Santaladchaiyakit, Yanawath; Srijaranai, Supalax

2014-11-01

Vortex-assisted dispersive liquid-liquid microextraction using methyl benzoate as an alternative extraction solvent for extracting and preconcentrating three benzimidazole fungicides (i.e., carbendazim, thiabendazole, and fluberidazole) in environmental water samples before high-performance liquid chromatographic analysis has been developed. The selected microextraction conditions were 250 μL of methyl benzoate containing 300 μL of ethanol, 1.0% w/v sodium acetate, and vortex agitation speed of 2100 rpm for 30 s. Under optimum conditions, preconcentration factors were 14.5-39.0 for the target fungicides. Limits of detection were obtained in the range of 0.01-0.05 μg/L. The proposed method was then applied to surface water samples and the recovery evaluations at three spiked concentration levels of 5, 30, and 50 μg/L were obtained in the range of 77.4-110.9% with the relative standard deviation <7.4%. The present method was simple, rapid, low cost, sensitive, environmentally friendly, and suitable for the trace analysis of the studied fungicides in environmental water samples. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theoretical study on second-harmonic generation of focused vortex beams

NASA Astrophysics Data System (ADS)

Tang, Daolong; Wang, Jing; Ma, Jingui; Zhou, Bingjie; Yuan, Peng; Xie, Guoqiang; Zhu, Heyuan; Qian, Liejia

2018-03-01

Second-harmonic generation (SHG) provides a promising route for generating vortex beams of both short wavelength and large topological charge. Here we theoretically investigate the efficiency optimization and beam characteristics of focused vortex-beam SHG. Owing to the increasing beam divergence, vortex beams have distinct features in SHG optimization compared with a Gaussian beam. We show that, under the noncritical phase-matching condition, the Boyd and Kleinman prediction of the optimal focusing parameter for Gaussian-beam SHG remains valid for vortex-beam SHG. However, under the critical phase-matching condition, which is sensitive to the beam divergence, the Boyd and Kleinman prediction is no longer valid. In contrast, the optimal focusing parameter for maximizing the SHG efficiency strongly depends on the vortex order. We also investigate the effects of focusing and phase-matching conditions on the second-harmonic beam characteristics.

Preemptive vortex-loop proliferation in multicomponent interacting Bose-Einstein condensates

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

Dahl, E. K.; Kragset, S.; Sudboe, A.

2008-04-01

We use analytical arguments and large-scale Monte Carlo calculations to investigate the nature of the phase transitions between distinct complex superfluid phases in a two-component Bose-Einstein condensate when a nondissipative drag between the two components is being varied. We focus on understanding the role of topological defects in various phase transitions and develop vortex-matter arguments, allowing an analytical description of the phase diagram. We find the behavior of fluctuation induced vortex matter to be much more complex and substantially different from that of single-component superfluids. We propose and numerically investigate a drag-induced ''preemptive vortex loop proliferation'' scenario. Such a transitionmore » may be a quite generic feature in many multicomponent systems where symmetry is restored by a gas of several kinds of competing vortex loops.« less

Reconstruction phases in the planar three- and four-vortex problems

NASA Astrophysics Data System (ADS)

Hernández-Garduño, Antonio; Shashikanth, Banavara N.

2018-03-01

Pure reconstruction phases—geometric and dynamic—are computed in the N-point-vortex model in the plane, for the cases N=3 and N=4 . The phases are computed relative to a metric-orthogonal connection on appropriately defined principal fiber bundles. The metric is similar to the kinetic energy metric for point masses but with the masses replaced by vortex strengths. The geometric phases are shown to be proportional to areas enclosed by the closed orbit on the symmetry reduced spaces. More interestingly, simple formulae are obtained for the dynamic phases, analogous to Montgomery’s result for the free rigid body, which show them to be proportional to the time period of the symmetry reduced closed orbits. For the case N = 3 a non-zero total vortex strength is assumed. For the case N = 4 the vortex strengths are assumed equal.

Molecular shear heating and vortex dynamics in thermostatted two dimensional Yukawa liquids

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

Gupta, Akanksha; Ganesh, Rajaraman, E-mail: ganesh@ipr.res.in; Joy, Ashwin

2016-07-15

It is well known that two-dimensional macroscale shear flows are susceptible to instabilities leading to macroscale vortical structures. The linear and nonlinear fate of such a macroscale flow in a strongly coupled medium is a fundamental problem. A popular example of a strongly coupled medium is a dusty plasma, often modelled as a Yukawa liquid. Recently, laboratory experiments and molecular dynamics (MD) studies of shear flows in strongly coupled Yukawa liquids indicated the occurrence of strong molecular shear heating, which is found to reduce the coupling strength exponentially leading to the destruction of macroscale vorticity. To understand the vortex dynamicsmore » of strongly coupled molecular fluids undergoing macroscale shear flows and molecular shear heating, MD simulation has been performed, which allows the macroscopic vortex dynamics to evolve, while at the same time “removes” the microscopically generated heat without using the velocity degrees of freedom. We demonstrate that by using a configurational thermostat in a novel way, the microscale heat generated by shear flow can be thermostatted out efficiently without compromising the large scale vortex dynamics. In the present work, using MD simulations, a comparative study of shear flow evolution in Yukawa liquids in the presence and absence of molecular or microscopic heating is presented for a prototype shear flow, namely, Kolmogorov flow.« less

Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

NASA Astrophysics Data System (ADS)

Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

2017-10-01

Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

Overlap of two topological phases in the antiferromagnetic Potts model

NASA Astrophysics Data System (ADS)

Zhao, Ran; Ding, Chengxiang; Deng, Youjin

2018-05-01

By controlling the vortex core energy, the three-state ferromagnetic Potts model can exhibit two types of topological paradigms, including the quasi-long-range ordered phase and the vortex lattice phase [Phys. Rev. Lett. 116, 097206 (2016), 10.1103/PhysRevLett.116.097206]. Here, using Monte Carlo simulations using an efficient worm algorithm, we show that by controlling the vortex core energy, the antiferromagnetic Potts model can also exhibit the two topological phases, and, more interestingly, the two topological phases can overlap with each other.

Numerical Simulations of Vortex Shedding in Hydraulic Turbines

NASA Technical Reports Server (NTRS)

Dorney, Daniel; Marcu, Bogdan

2004-01-01

Turbomachines for rocket propulsion applications operate with many different working fluids and flow conditions. Oxidizer boost turbines often operate in liquid oxygen, resulting in an incompressible flow field. Vortex shedding from airfoils in this flow environment can have adverse effects on both turbine performance and durability. In this study the effects of vortex shedding in a low-pressure oxidizer turbine are investigated. Benchmark results are also presented for vortex shedding behind a circular cylinder. The predicted results are compared with available experimental data.

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

NASA Astrophysics Data System (ADS)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-03-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

NASA Astrophysics Data System (ADS)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-06-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Dynamics of levitated objects in acoustic vortex fields.

PubMed

Hong, Z Y; Yin, J F; Zhai, W; Yan, N; Wang, W L; Zhang, J; Drinkwater, Bruce W

2017-08-02

Acoustic levitation in gaseous media provides a tool to process solid and liquid materials without the presence of surfaces such as container walls and hence has been used widely in chemical analysis, high-temperature processing, drop dynamics and bioreactors. To date high-density objects can only be acoustically levitated in simple standing-wave fields. Here we demonstrate the ability of a small number of peripherally placed sources to generate acoustic vortex fields and stably levitate a wide range of liquid and solid objects. The forces exerted by these acoustic vortex fields on a levitated water droplet are observed to cause a controllable deformation of the droplet and/or oscillation along the vortex axis. Orbital angular momentum transfer is also shown to rotate a levitated object rapidly and the rate of rotation can be controlled by the source amplitude. We expect this research can increase the diversity of acoustic levitation and expand the application of acoustic vortices.

Vortex-assisted emulsification semimicroextraction for the analytical control of restricted ingredients in cosmetic products: determination of bronopol by liquid chromatography.

PubMed

Miralles, Pablo; Bellver, Raquel; Chisvert, Alberto; Salvador, Amparo

2016-03-01

Vortex-assisted emulsification semimicroextraction is proposed as a one-step solution-extraction procedure for sample preparation in cosmetic products. The procedure allows rapid preparation based on dispersion of the sample in a mixture of 1 mL of n-hexane and 0.5 mL of ethanol, followed by the addition of 0.5 mL of water and centrifugation to obtain two separated phases. This procedure provides good sample clean-up with minimum dilution and is very useful for the determination of ingredients with restricted concentrations, such as bronopol. The procedure was applied to the determination of bronopol by liquid chromatography with UV detection. The best chromatographic separation was obtained by using a C18 column set at 40 °C and performing a stepwise elution with a mixture of ethanol/aqueous 1 % acetic acid solution as mobile phase pumped at 0.5 mL min(-1). The detection wavelength was set at 250 nm and the total run time required was 12 min. The method was successfully applied to 18 commercial cosmetic samples including creams, shampoos, and bath gels. Good recoveries and repeatability were obtained, with a limit of detection of 0.9 μg mL(-1), which makes the method suitable for the analytical control of cosmetic products. Moreover, it could be considered environmentally friendly, because water, ethanol, and only a low volume of n-hexane are used as solvents.

Vectoring of parallel synthetic jets

NASA Astrophysics Data System (ADS)

Berk, Tim; Ganapathisubramani, Bharathram; Gomit, Guillaume

2015-11-01

A pair of parallel synthetic jets can be vectored by applying a phase difference between the two driving signals. The resulting jet can be merged or bifurcated and either vectored towards the actuator leading in phase or the actuator lagging in phase. In the present study, the influence of phase difference and Strouhal number on the vectoring behaviour is examined experimentally. Phase-locked vorticity fields, measured using Particle Image Velocimetry (PIV), are used to track vortex pairs. The physical mechanisms that explain the diversity in vectoring behaviour are observed based on the vortex trajectories. For a fixed phase difference, the vectoring behaviour is shown to be primarily influenced by pinch-off time of vortex rings generated by the synthetic jets. Beyond a certain formation number, the pinch-off timescale becomes invariant. In this region, the vectoring behaviour is determined by the distance between subsequent vortex rings. We acknowledge the financial support from the European Research Council (ERC grant agreement no. 277472).

Soot and liquid-phase fuel distributions in a newly designed optically accessible DI diesel engine

NASA Astrophysics Data System (ADS)

Dec, J. E.; Espey, C.

1993-10-01

Two-dimensional (2-D) laser-sheet imaging has been used to examine the soot and liquid-phase fuel distributions in a newly designed, optically accessible, direct-injection diesel engine of the heavy-duty size class. The design of this engine preserves the intake port geometry and basic dimensions of a Cummins N-series production engine. It also includes several unique features to provide considerable optical access. Liquid-phase fuel and soot distribution studies were conducted at a medium speed (1,200 rpm) using a Cummins closed-nozzle fuel injector. The scattering was used to obtain planar images of the liquid-phase fuel distribution. These images show that the leading edge of the liquid-phase portion of the fuel jet reaches a maximum length of 24 mm, which is about half the combustion bowl radius for this engine. Beyond this point virtually all the fuel has vaporized. Soot distribution measurements were made at a high load condition using three imaging diagnostics: natural flame luminosity, 2-D laser-induced incandescence, and 2-D elastic scattering. This investigation showed that the soot distribution in the combusting fuel jet develops through three stages. First, just after the onset of luminous combustion, soot particles are small and nearly uniformly distributed throughout the luminous region of the fuel jet. Second, after about 2 crank angle degrees a pattern develops of a higher soot concentration of larger sized particles in the head vortex region of the jet and a lower soot concentration of smaller sized particles upstream toward the injector. Third, after fuel injection ends, both the soot concentration and soot particle size increase rapidly in the upstream portion of the fuel jet.

Measuring Orbital Angular Momentum (OAM) States of Vortex Beams with Annular Gratings

PubMed Central

Zheng, Shuang; Wang, Jian

2017-01-01

Measuring orbital angular momentum (OAM) states of vortex beams is of great importance in diverse applications employing OAM-carrying vortex beams. We present a simple and efficient scheme to measure OAM states (i.e. topological charge values) of vortex beams with annular gratings. The magnitude of the topological charge value is determined by the number of dark fringes after diffraction, and the sign of the topological charge value is distinguished by the orientation of the diffraction pattern. We first theoretically study the diffraction patterns using both annular amplitude and phase gratings. The annular phase grating shows almost 10-dB better diffraction efficiency compared to the annular amplitude grating. We then experimentally demonstrate the OAM states measurement of vortex beams using annular phase grating. The scheme works well even for high-order vortex beams with topological charge value as high as ± 25. We also experimentally show the evolution of diffraction patterns when slightly changing the fractional topological charge value of vortex beam from 0.1 to 1.0. In addition, the proposed scheme shows potential large tolerance of beam alignment during the OAM states measurement of vortex beams. PMID:28094325

Measuring Orbital Angular Momentum (OAM) States of Vortex Beams with Annular Gratings.

PubMed

Zheng, Shuang; Wang, Jian

2017-01-17

Measuring orbital angular momentum (OAM) states of vortex beams is of great importance in diverse applications employing OAM-carrying vortex beams. We present a simple and efficient scheme to measure OAM states (i.e. topological charge values) of vortex beams with annular gratings. The magnitude of the topological charge value is determined by the number of dark fringes after diffraction, and the sign of the topological charge value is distinguished by the orientation of the diffraction pattern. We first theoretically study the diffraction patterns using both annular amplitude and phase gratings. The annular phase grating shows almost 10-dB better diffraction efficiency compared to the annular amplitude grating. We then experimentally demonstrate the OAM states measurement of vortex beams using annular phase grating. The scheme works well even for high-order vortex beams with topological charge value as high as ± 25. We also experimentally show the evolution of diffraction patterns when slightly changing the fractional topological charge value of vortex beam from 0.1 to 1.0. In addition, the proposed scheme shows potential large tolerance of beam alignment during the OAM states measurement of vortex beams.

Evaluation of Impinging Stream Vortex Chamber Concepts for Liquid Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Trinh, Huu; Kopicz, Charles; Bullard, Brad; Michaels, Scott

2003-01-01

NASA Marshall Space Flight Center (MSFC) and the U. S. Army are jointly investigating vortex chamber concepts for cryogenic oxygen/hydrocarbon fuel rocket engine applications. One concept, the Impinging Stream Vortex Chamber Concept (ISVC), has been tested with gel propellants at AMCOM at Redstone Arsenal, Alabama. A version of this concept for the liquid oxygen (LOX)/hydrocarbon fuel (RP-1) propellant system is derived from the one for the gel propellant. An unlike impinging injector is employed to deliver the propellants to the chamber. MSFC has also designed two alternative injection schemes, called the chasing injectors, associated with this vortex chamber concept. In these injection techniques, both propellant jets and their impingement point are in the same chamber cross-sectional plane. One injector has a similar orifice size with the original unlike impinging injector. The second chasing injector has small injection orifices. The team has achieved their objectives of demonstrating the self-cooled chamber wall benefits of ISVC and of providing the test data for validating computational fluids dynamics (CFD) models. These models, in turn, will be used to design the optimum vortex chambers in the future.

Vortex interaction with a leading-edge of finite thickness

NASA Technical Reports Server (NTRS)

Sohn, D.; Rockwell, Donald

1987-01-01

Vortex interaction with a thick elliptical leading-edge at zero relative offset produces a pronounced secondary vortes of opposite sense that travels with the same phase speed as the primaty vortex along the lower surface of the edge. The edge thickness (scale) relative to the incident vorticity field has a strong effect on the distortion of the incident primary vortex during the impingement processs. When the thickness is sufficiently small, there is a definite severing of the incident vortex and the portion of the incident vortex that travels along the upper part of the elliptical surface has a considerably larger phase speed than that along the lower surface; this suggests that the integrated loading along the upper surface is more strongly correlated. When the thickness becomes too large, then most, if not all, of the incident vortex passes below the leading-edge. On the other hand, the relative tranverse offset of the edge with respect to the center of the incident vortex has a significant effect on the secondary vortex formation.

Atmospheric study of the impact of Borneo vortex and Madden-Julian oscillation over Western Indonesian maritime area

NASA Astrophysics Data System (ADS)

Saragih, R. M.; Fajarianti, R.; Winarso, P. A.

2018-03-01

During the Asian winter Monsoon (November-March), the Indonesia Maritime Continent is an area of deep convection. In that period, there is a synoptic scale disturbance over Northwest of Borneo Island called Borneo vortex. In addition to the impact of Asian Winter Monsoon, Madden-Julian Oscillation (MJO) also have an impact on deep convection during an active period. This study aims to study the impact of interaction Borneo vortex and MJO (during MJO active period in phase 3, 4 and 5) and rainfall condition over the western part of Indonesia Maritime Continent using compositing technique in the period of November-March 2015/2016. The parameters used to identify the incidence of Borneo vortex, MJO, and its interaction is vertical velocity. When MJO is active, Borneo vortex occurs most often in phase 5 and at least in phase 3. However, Borneo vortex occurs most often when the MJO is inactive. The interaction between Borneo vortex and MJO seems may affect not so much rainfall occurrence in the western part of IMC.

Zero liquid carryover whole-body shower vortex liquid/gas separator

NASA Technical Reports Server (NTRS)

1975-01-01

The development and evaluation of a liquid/gas vortex type separator design eliminating liquid and semi-liquid (suds) carryover into air recirculating system were described. Consideration was given to a number of soaps other than the "Miranol JEM" which was the low sudsing soap used in previous test runs of the space shower. Analysis of test parameters and prototype testing resulted in a revised separator configuration and a better understanding of the suds generating mechanism in the wastewater collection system. The final design of the new separator provides for a wider choice of soaps without leading to the problem of "carryover". Furthermore, no changes in separator-to-shower interfaces were required. The new separator was retrofitted on the "space shower" and satisfactorily demonstrated in one-g testing.

Transmission Geometry Laser Ablation into a Non-Contact Liquid Vortex Capture Probe for Mass Spectrometry Imaging

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

Ovchinnikova, Olga S; Bhandari, Deepak; Lorenz, Matthias

2014-01-01

RATIONALE: Capture of material from a laser ablation plume into a continuous flow stream of solvent provides the means for uninterrupted sampling, transport and ionization of collected material for coupling with mass spectral analysis. Reported here is the use of vertically aligned transmission geometry laser ablation in combination with a new non-contact liquid vortex capture probe coupled with electrospray ionization for spot sampling and chemical imaging with mass spectrometry. Methods: A vertically aligned continuous flow liquid vortex capture probe was positioned directly underneath a sample surface in a transmission geometry laser ablation (355 nm, 10 Hz, 7 ns pulse width)more » setup to capture into solution the ablated material. The outlet of the vortex probe was coupled to the Turbo V ion source of an AB SCIEX TripleTOF 5600+ mass spectrometer. System operation and performance metrics were tested using inked patterns and thin tissue sections. Glass slides and slides designed especially for laser capture microdissection, viz., DIRECTOR slides and PEN 1.0 (polyethylene naphthalate) membrane slides, were used as sample substrates. Results: The estimated capture efficiency of laser ablated material was 24%, which was enabled by the use of a probe with large liquid surface area (~ 2.8 mm2) and with gravity to help direct ablated material vertically down towards the probe. The swirling vortex action of the liquid surface potentially enhanced capture and dissolution of not only particulates, but also gaseous products of the laser ablation. The use of DIRECTOR slides and PEN 1.0 (polyethylene naphthalate) membrane slides as sample substrates enabled effective ablation of a wide range of sample types (basic blue 7, polypropylene glycol, insulin and cyctochrome c) without photodamage using a UV laser. Imaging resolution of about 6 m was demonstrated for stamped ink on DIRECTOR slides based on the ability to distinguish features present both in the optical and in the chemical image. This imaging resolution was 20 times better than the previous best reported results with laser ablation/liquid sample capture mass spectrometry imaging. Using thin sections of brain tissue the chemical image of a selected lipid was obtained with an estimated imaging resolution of about 50 um. Conclusions: A vertically aligned, transmission geometry laser ablation liquid vortex capture probe, electrospray ionization mass spectrometry system provides an effective means for spatially resolved spot sampling and imaging with mass spectrometry.« less

Transmission geometry laser ablation into a non-contact liquid vortex capture probe for mass spectrometry imaging.

PubMed

Ovchinnikova, Olga S; Bhandari, Deepak; Lorenz, Matthias; Van Berkel, Gary J

2014-08-15

Capture of material from a laser ablation plume into a continuous flow stream of solvent provides the means for uninterrupted sampling, transport and ionization of collected material for coupling with mass spectral analysis. Reported here is the use of vertically aligned transmission geometry laser ablation in combination with a new non-contact liquid vortex capture probe coupled with electrospray ionization for spot sampling and chemical imaging with mass spectrometry. A vertically aligned continuous flow liquid vortex capture probe was positioned directly underneath a sample surface in a transmission geometry laser ablation (355 nm, 10 Hz, 7 ns pulse width) set up to capture into solution the ablated material. The outlet of the vortex probe was coupled to the Turbo V™ ion source of an AB SCIEX TripleTOF 5600+ mass spectrometer. System operation and performance metrics were tested using inked patterns and thin tissue sections. Glass slides and slides designed especially for laser capture microdissection, viz., DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides, were used as sample substrates. The estimated capture efficiency of laser-ablated material was 24%, which was enabled by the use of a probe with large liquid surface area (~2.8 mm(2) ) and with gravity to help direct ablated material vertically down towards the probe. The swirling vortex action of the liquid surface potentially enhanced capture and dissolution not only of particulates, but also of gaseous products of the laser ablation. The use of DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides as sample substrates enabled effective ablation of a wide range of sample types (basic blue 7, polypropylene glycol, insulin and cyctochrome c) without photodamage using a UV laser. Imaging resolution of about 6 µm was demonstrated for stamped ink on DIRECTOR(®) slides based on the ability to distinguish features present both in the optical and in the chemical image. This imaging resolution was 20 times better than the previous best reported results with laser ablation/liquid sample capture mass spectrometry imaging. Using thin sections of brain tissue the chemical image of a selected lipid was obtained with an estimated imaging resolution of about 50 µm. A vertically aligned, transmission geometry laser ablation liquid vortex capture probe, electrospray ionization mass spectrometry system provides an effective means for spatially resolved spot sampling and imaging with mass spectrometry. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA.

An H-band Vector Vortex Coronagraph for the Subaru Coronagraphic Extreme-adaptive Optics System

NASA Astrophysics Data System (ADS)

Kühn, J.; Serabyn, E.; Lozi, J.; Jovanovic, N.; Currie, T.; Guyon, O.; Kudo, T.; Martinache, F.; Liewer, K.; Singh, G.; Tamura, M.; Mawet, D.; Hagelberg, J.; Defrere, D.

2018-03-01

The vector vortex is a coronagraphic imaging mode of the recently commissioned Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) platform on the 8 m Subaru Telescope. This multi-purpose high-contrast visible and near-infrared (R- to K-band) instrument is not only intended to serve as a VLT-class “planet-imager” instrument in the northern hemisphere, but also to operate as a technology demonstration testbed ahead of the ELTs-era, with a particular emphasis on small inner-working angle (IWA) coronagraphic capabilities. The given priority to small-IWA imaging led to the early design choice to incorporate focal-plane phase-mask coronagraphs. In this context, a test H-band vector vortex liquid crystal polymer waveplate was provided to SCExAO, to allow a one-to-one comparison of different small-IWA techniques on the same telescope instrument, before considering further steps. Here we present a detailed overview of the vector vortex coronagraph, from its installation and performances on the SCExAO optical bench, to the on-sky results in the extreme AO regime, as of late 2016/early 2017. To this purpose, we also provide a few recent on-sky imaging examples, notably high-contrast ADI detection of the planetary-mass companion κ Andromedae b, with a signal-to-noise ratio above 100 reached in less than 10 mn exposure time.

Nonequilibrium dynamic phases in driven vortex lattices with periodic pinning

NASA Astrophysics Data System (ADS)

Reichhardt, Charles Michael

1998-12-01

We present the results of an extensive series of simulations of flux-gradient and current driven vortices interacting with either random or periodically arranged pinning sites. First, we consider flux-gradient-driven simulations of superconducting vortices interacting with strong randomly-distributed columnar pinning defects, as an external field H(t) is quasi-statically swept from zero through a matching field Bsb{phi}. Here, we find significant changes in the behavior of the local flux density B(x, y, H(t)), magnetization M(H(t)), critical current Jsb{c}(B(t)), and the individual vortex flow paths, as the local flux density crosses Bsb{phi}. Further, we find that for a given pin density, Jsb{c}(B) can be enhanced by maximizing the distance between the pins for B < Bsb{phi}. For the case of periodic pinning sites as a function of applied field, we find a rich variety of ordered and partially-ordered vortex lattice configurations. We present formulas that predict the matching fields at which commensurate vortex configurations occur and the vortex lattice orientation with respect to the pinning lattice. Our results are in excellent agreement with recent imaging experiments on square pinning arrays (K. Harada et al., Science 274, 1167 (1996)). For current driven simulations with periodic pinning we find a remarkable number of dynamical plastic flow phases. Signatures of the transitions between these different dynamical phases include sudden jumps in the current-voltage curves, hysteresis, as well as marked changes in the vortex trajectories and vortex lattice order. These phases are outlined in a series of dynamic phase diagrams. We show that several of these phases and their phase-boundaries can be understood in terms of analytical arguments. Finally, when the vortex lattice is driven at varying angles with respect to the underlying periodic pinning array, the transverse voltage-current V(I) curves show a series of mode-locked plateaus with the overall V(I) forming a devil's staircase structure.

Modeling of Quasi-Four-Phase Flow in Continuous Casting Mold Using Hybrid Eulerian and Lagrangian Approach

NASA Astrophysics Data System (ADS)

Liu, Zhongqiu; Sun, Zhenbang; Li, Baokuan

2017-04-01

Lagrangian tracking model combined with Eulerian multi-phase model is employed to predict the time-dependent argon-steel-slag-air quasi-four-phase flow inside a slab continuous casting mold. The Eulerian approach is used for the description of three phases (molten steel, liquid slag, and air at the top of liquid slag layer). The dispersed argon bubble injected from the SEN is treated in the Lagrangian way. The complex interfacial momentum transfers between various phases are considered. Validation is supported by the measurement data of cold model experiments and industrial practice. Close agreements were achieved for the gas volume fraction, liquid flow pattern, level fluctuation, and exposed slag eye phenomena. Many known phenomena and new predictions were successfully reproduced using this model. The vortex slag entrapment phenomenon at the slag-steel interface was obtained using this model, some small slag drops are sucked deep into the liquid pool of molten steel. Varying gas flow rates have a large effect on the steel flow pattern in the upper recirculation zone. Three typical flow patterns inside the mold with different argon gas flow rates have been obtained: double roll, three roll, and single roll. Effects of argon gas flow rate, casting speed, and slag layer thickness on the exposed slag eye and level fluctuation at the slag-steel interface were studied. A dimensionless value of H ave/ h was proposed to describe the time-averaged level fluctuation of slag-steel interface. The exposed slag eye near the SEN would be formed when the value of H ave/ h is larger than 0.4.

A simple, rapid and novel method based on salting-out assisted liquid-liquid extraction for ochratoxin A determination in beer samples prior to ultra-high performance liquid chromatography coupled to tandem mass spectrometry.

PubMed

Mariño-Repizo, Leonardo; Goicoechea, Hector; Raba, Julio; Cerutti, Soledad

2018-06-07

A novel, simple, easy and cheap sample treatment strategy based on salting-out assisted liquid-liquid extraction (SALLE) for ochratoxin A (OTA) ultra-trace analysis in beer samples using ultra-high performance liquid chromatography-tandem mass spectrometry determination was developed. The factors involved in the efficiency of pretreatment were studied employing factorial design in the screening phase and the optimal conditions of the significant variables on the analytical response were evaluated using a central composite face-centred design (CCF). Consequently, the amount of salt ((NH 4 ) 2 SO 4 ), together with the volumes of sample, hydrophilic (acetone) and nonpolar (toluene) solvents, and times of vortexing and centrifugation were optimized. Under optimized conditions, the limits of detection (LOD) and quantification (LOQ) were 0.02 µg l -1 and 0.08 µg l -1 respectively. OTA extraction recovery by SALLE was approximately 90% (0.2 µg l -1 ). Furthermore, the methodology was in agreement with EU Directive requirements and was successfully applied for analysis of beer samples.

Visualization of vortex structures and analysis of frequency of PVC

NASA Astrophysics Data System (ADS)

Gesheva, E. S.; Shtork, S. I.; Alekseenko, S. V.

2018-03-01

The paper presents the results of the study of large-scale vortex structures in a model chamber. Methods of forming quasi-stationary vortices of various shapes by changing the geometric parameters of the chamber have been proposed. In the model chamber with a tangential swirl of the flow, a rectilinear vortex, single helical and double helical vortices were obtained. The double helical structure of the vortex is unique due to its immovability around the axis of the chamber. The resulting structures slowly oscillate around their own axes, which is called the vortex core precession; while the oscillation frequency depends linearly on the liquid flow rate. The use of stationary vortex structures in power plants will increase the efficiency of combustion chambers and reduce slagging.

Evolution of diffraction and self-diffraction phenomena in thin films of Gelite Bloom/Hibiscus Sabdariffa

NASA Astrophysics Data System (ADS)

Cano-Lara, Miroslava; Severiano-Carrillo, Israel; Trejo-Durán, Mónica; Alvarado-Méndez, Edgar

2017-09-01

In this work, we present a study of non-linear optical response in thin films elaborated with Gelite Bloom and extract of Hibiscus Sabdariffa. Non-linear refraction and absorption effects were studied experimentally (Z-scan technique) and numerically, by considering the transmittance as non-linear absorption and refraction contribution. We observe large phase shifts to far field, and diffraction due to self-phase modulation of the sample. Diffraction and self-diffraction effects were observed as time function. The aim of studying non-linear optical properties in thin films is to eliminate thermal vortex effects that occur in liquids. This is desirable in applications such as non-linear phase contrast, optical limiting, optics switches, etc. Finally, we find good agreement between experimental and theoretical results.

The Nernst effect in layered superconductors under a magnetic field

NASA Astrophysics Data System (ADS)

Tinh, Bui Duc; Thu, Le Minh; Hoc, Nguyen Quang

2016-08-01

We calculated the Nernst signal eN, describing the Nernst effect in type-II superconductor in the vortex-liquid regime, by using the time-dependent Ginzburg-Landau (TDGL) equation with thermal noise. The nonlinear interaction term in the TDGL equation is treated within self-consistent Gaussian approximation. The expression of the Nernst signal eN including all the Landau levels is presented in explicit form which is applicable essentially to the whole phase. Our results are compared with the recent experimental data on high-Tc superconductor.

Creation of diffraction-limited non-Airy multifocal arrays using a spatially shifted vortex beam

NASA Astrophysics Data System (ADS)

Lin, Han; Gu, Min

2013-02-01

Diffraction-limited non-Airy multifocal arrays are created by focusing a phase-modulated vortex beam through a high numerical-aperture objective. The modulated phase at the back aperture of the objective resulting from the superposition of two concentric phase-modulated vortex beams allows for the generation of a multifocal array of cylindrically polarized non-Airy patterns. Furthermore, we shift the spatial positions of the phase vortices to manipulate the intensity distribution at each focal spot, leading to the creation of a multifocal array of split-ring patterns. Our method is experimentally validated by generating the predicted phase modulation through a spatial light modulator. Consequently, the spatially shifted circularly polarized vortex beam adopted in a dynamic laser direct writing system facilitates the fabrication of a split-ring microstructure array in a polymer material by a single exposure of a femtosecond laser beam.

Symmetry-broken states in a system of interacting bosons on a two-leg ladder with a uniform Abelian gauge field

NASA Astrophysics Data System (ADS)

Greschner, S.; Piraud, M.; Heidrich-Meisner, F.; McCulloch, I. P.; Schollwöck, U.; Vekua, T.

2016-12-01

We study the quantum phases of bosons with repulsive contact interactions on a two-leg ladder in the presence of a uniform Abelian gauge field. The model realizes many interesting states, including Meissner phases, vortex fluids, vortex lattices, charge density waves, and the biased-ladder phase. Our work focuses on the subset of these states that breaks a discrete symmetry. We use density matrix renormalization group simulations to demonstrate the existence of three vortex-lattice states at different vortex densities and we characterize the phase transitions from these phases into neighboring states. Furthermore, we provide an intuitive explanation of the chiral-current reversal effect that is tied to some of these vortex lattices. We also study a charge-density-wave state that exists at 1/4 particle filling at large interaction strengths and flux values close to half a flux quantum. By changing the system parameters, this state can transition into a completely gapped vortex-lattice Mott-insulating state. We elucidate the stability of these phases against nearest-neighbor interactions on the rungs of the ladder relevant for experimental realizations with a synthetic lattice dimension. A charge-density-wave state at 1/3 particle filling can be stabilized for flux values close to half a flux quantum and for very strong on-site interactions in the presence of strong repulsion on the rungs. Finally, we analytically describe the emergence of these phases in the low-density regime, and, in particular, we obtain the boundaries of the biased-ladder phase, i.e., the phase that features a density imbalance between the legs. We make contact with recent quantum-gas experiments that realized related models and discuss signatures of these quantum states in experimentally accessible observables.

Origin and dynamics of vortex rings in drop splashing

DOE PAGES

Lee, Ji San; Park, Su Ji; Lee, Jun Ho; ...

2015-09-04

A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row ofmore » vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.« less

Origin and dynamics of vortex rings in drop splashing.

PubMed

Lee, Ji San; Park, Su Ji; Lee, Jun Ho; Weon, Byung Mook; Fezzaa, Kamel; Je, Jung Ho

2015-09-04

A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row of vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.

Origin and dynamics of vortex rings in drop splashing

PubMed Central

Lee, Ji San; Park, Su Ji; Lee, Jun Ho; Weon, Byung Mook; Fezzaa, Kamel; Je, Jung Ho

2015-01-01

A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row of vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing. PMID:26337704

Phase and vortex correlations in superconducting Josephson-junction arrays at irrational magnetic frustration.

PubMed

Granato, Enzo

2008-07-11

Phase coherence and vortex order in a Josephson-junction array at irrational frustration are studied by extensive Monte Carlo simulations using the parallel-tempering method. A scaling analysis of the correlation length of phase variables in the full equilibrated system shows that the critical temperature vanishes with a power-law divergent correlation length and critical exponent nuph, in agreement with recent results from resistivity scaling analysis. A similar scaling analysis for vortex variables reveals a different critical exponent nuv, suggesting that there are two distinct correlation lengths associated with a decoupled zero-temperature phase transition.

Dual gauge field theory of quantum liquid crystals in three dimensions

DOE PAGES

Beekman, Aron J.; Nissinen, Jaakko; Wu, Kai; ...

2017-10-09

The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emergemore » whenever translational symmetry is restored. Lastly, we also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.« less

Dual gauge field theory of quantum liquid crystals in three dimensions

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

Beekman, Aron J.; Nissinen, Jaakko; Wu, Kai

The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emergemore » whenever translational symmetry is restored. Lastly, we also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.« less

Exact results for the star lattice chiral spin liquid

NASA Astrophysics Data System (ADS)

Kells, G.; Mehta, D.; Slingerland, J. K.; Vala, J.

2010-03-01

We examine the star lattice Kitaev model whose ground state is a chiral spin liquid. We fermionize the model such that the fermionic vacua are toric-code states on an effective Kagome lattice. This implies that the Abelian phase of the system is inherited from the fermionic vacua and that time-reversal symmetry is spontaneously broken at the level of the vacuum. In terms of these fermions we derive the Bloch-matrix Hamiltonians for the vortex-free sector and its time-reversed counterpart and illuminate the relationships between the sectors. The phase diagram for the model is shown to be a sphere in the space of coupling parameters around the triangles of the lattices. The Abelian phase lies inside the sphere and the critical boundary between topologically distinct Abelian and non-Abelian phases lies on the surface. Outside the sphere the system is generically gapped except in the planes where the coupling parameters between the vertices on triangles are zero. These cases correspond to bipartite lattice structures and the dispersion relations are similar to that of the original Kitaev honeycomb model. In a further analysis we demonstrate the threefold non-Abelian ground-state degeneracy on a torus by explicit calculation.

Selective equal spin Andreev reflection at vortex core center in magnetic semiconductor-superconductor heterostructure.

PubMed

Li, Chuang; Hu, Lun-Hui; Zhou, Yi; Zhang, Fu-Chun

2018-05-18

Sau, Lutchyn, Tewari and Das Sarma (SLTD) proposed a heterostructure consisting of a semiconducting thin film sandwiched between an s-wave superconductor and a magnetic insulator and showed possible Majorana zero mode. Here we study spin polarization of the vortex core states and spin selective Andreev reflection at the vortex center of the SLTD model. In the topological phase, the differential conductance at the vortex center contributed from the Andreev reflection, is spin selective and has a quantized value [Formula: see text] at zero bias. In the topological trivial phase, [Formula: see text] at the lowest quasiparticle energy of the vortex core is spin selective due to the spin-orbit coupling (SOC). Unlike in the topological phase, [Formula: see text] is suppressed in the Giaever limit and vanishes exactly at zero bias due to the quantum destruction interference.

Vortex mass in a superfluid

NASA Astrophysics Data System (ADS)

Simula, Tapio

2018-02-01

We consider the inertial mass of a vortex in a superfluid. We obtain a vortex mass that is well defined and is determined microscopically and self-consistently by the elementary excitation energy of the kelvon quasiparticle localized within the vortex core. The obtained result for the vortex mass is found to be consistent with experimental observations on superfluid quantum gases and vortex rings in water. We propose a method to measure the inertial rest mass and Berry phase of a vortex in superfluid Bose and Fermi gases.

Phase coexistence and electric-field control of toroidal order in oxide superlattices.

PubMed

Damodaran, A R; Clarkson, J D; Hong, Z; Liu, H; Yadav, A K; Nelson, C T; Hsu, S-L; McCarter, M R; Park, K-D; Kravtsov, V; Farhan, A; Dong, Y; Cai, Z; Zhou, H; Aguado-Puente, P; García-Fernández, P; Íñiguez, J; Junquera, J; Scholl, A; Raschke, M B; Chen, L-Q; Fong, D D; Ramesh, R; Martin, L W

2017-10-01

Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO 3 /SrTiO 3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a 1 /a 2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities.

Phase coexistence and electric-field control of toroidal order in oxide superlattices

NASA Astrophysics Data System (ADS)

Damodaran, A. R.; Clarkson, J. D.; Hong, Z.; Liu, H.; Yadav, A. K.; Nelson, C. T.; Hsu, S.-L.; McCarter, M. R.; Park, K.-D.; Kravtsov, V.; Farhan, A.; Dong, Y.; Cai, Z.; Zhou, H.; Aguado-Puente, P.; García-Fernández, P.; Íñiguez, J.; Junquera, J.; Scholl, A.; Raschke, M. B.; Chen, L.-Q.; Fong, D. D.; Ramesh, R.; Martin, L. W.

2017-10-01

Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO3/SrTiO3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a1/a2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities.

Customised spatiotemporal temperature gradients created by a liquid metal enabled vortex generator.

PubMed

Zhu, Jiu Yang; Thurgood, Peter; Nguyen, Ngan; Ghorbani, Kamran; Khoshmanesh, Khashayar

2017-11-07

Generating customised temperature gradients in miniaturised flow-free liquid chambers is challenging due to the dominance of diffusion. Inducing internal flows in the form of vortices is an effective strategy for overcoming the limitations of diffusion in such environments. Vortices can be produced by applying pressure, temperature and electric potential gradients via miniaturised actuators. However, the difficulties associated with the fabrication, integration, maintenance and operation of such actuators hinder their utility. Here, we utilise liquid metal enabled pumps to induce vortices inside a miniaturised liquid chamber. The configuration and rotational velocity of these vortices can be controlled by tuning the polarity and frequency of the energising electrical signal. This allows creation of customised spatial temperature gradients inside the chamber. The absence of conventional moving elements in the pumps facilitates the rapid reconfiguration of vortices. This enables quick transition from one temperature profile to another, and creates customised spatiotemporal temperature gradients. This allows temperature oscillation from 35 to 62 °C at the hot spot, and from 25 to 27 °C at the centre of the vortex within 15 seconds. Our liquid metal enabled vortex generator can be fabricated, integrated and operated easily, and offers opportunities for studying thermo-responsive materials and biological samples.

BKT phase transition in a 2D system with long-range dipole-dipole interaction

NASA Astrophysics Data System (ADS)

Fedichev, P. O.; Men'shikov, L. I.

2012-01-01

We consider phase transitions in 2D XY-like systems with long-range dipole-dipole interactions and demonstrate that BKT-type phase transition always occurs separating the ordered (ferroelectric) and the disordered (paraelectric) phases. The low-temperature phase corresponds to a thermal state with bound vortex-antivortex pairs characterized by linear attraction at large distances. Using the Maier-Schwabl topological charge model, we show that bound vortex pairs polarize and screen the vortex-antivortex interaction, leaving only the logarithmic attraction at sufficiently large separations between the vortices. At higher temperatures the pairs dissociate and the phase transition similar to BKT occurs, though at a larger temperature than in a system without the dipole-dipole interaction.

Generation of high-order Bessel vortex beam carrying orbital angular momentum using multilayer amplitude-phase-modulated surfaces in radiofrequency domain

NASA Astrophysics Data System (ADS)

Kou, Na; Yu, Shixing; Li, Long

2017-01-01

A high-order Bessel vortex beam carrying orbital angular momentum (OAM) is generated by using multilayer amplitude-phase-modulated surfaces (APMSs) at 10 GHz. The APMS transmitarray is composed of four-layer conformal square-loop (FCSL) surfaces with both amplitude and phase modulation. The APMS can transform a quasi-spherical wave emitted from the feeding source into a pseudo non-diffractive high-order Bessel vortex beam with OAM. The APMS for a second-order Bessel beam carrying OAM in the n = 2 mode is designed, fabricated, and measured. Full-wave simulation and measurement results confirm that Bessel vortex beams with OAM can be effectively generated using the proposed APMS transmitarray.

Force balance on two-dimensional superconductors with a single moving vortex

NASA Astrophysics Data System (ADS)

Chung, Chun Kit; Arahata, Emiko; Kato, Yusuke

2014-03-01

We study forces on two-dimensional superconductors with a single moving vortex based on a recent fully self-consistent calculation of DC conductivity in an s-wave superconductor (E. Arahata and Y. Kato, arXiv:1310.0566). By considering momentum balance of the whole liquid, we attempt to identify various contributions to the total transverse force on the vortex. This provides an estimation of the effective Magnus force based on the quasiclassical theory generalized by Kita [T. Kita, Phys. Rev. B, 64, 054503 (2001)], which allows for the Hall effect in vortex states.

RANS computations of tip vortex cavitation

NASA Astrophysics Data System (ADS)

Decaix, Jean; Balarac, Guillaume; Dreyer, Matthieu; Farhat, Mohamed; Münch, Cécile

2015-12-01

The present study is related to the development of the tip vortex cavitation in Kaplan turbines. The investigation is carried out on a simplified test case consisting of a NACA0009 blade with a gap between the blade tip and the side wall. Computations with and without cavitation are performed using a R ANS modelling and a transport equation for the liquid volume fraction. Compared with experimental data, the R ANS computations turn out to be able to capture accurately the development of the tip vortex. The simulations have also highlighted the influence of cavitation on the tip vortex trajectory.

Highly intense monocycle terahertz vortex generation by utilizing a Tsurupica spiral phase plate

PubMed Central

Miyamoto, Katsuhiko; Kang, Bong Joo; Kim, Won Tae; Sasaki, Yuta; Niinomi, Hiromasa; Suizu, Koji; Rotermund, Fabian; Omatsu, Takashige

2016-01-01

Optical vortex, possessing an annular intensity profile and an orbital angular momentum (characterized by an integer termed a topological charge) associated with a helical wavefront, has attracted great attention for diverse applications due to its unique properties. In particular for terahertz (THz) frequency range, several approaches for THz vortex generation, including molded phase plates consisting of metal slit antennas, achromatic polarization elements and binary-diffractive optical elements, have been recently proposed, however, they are typically designed for a specific frequency. Here, we demonstrate highly intense broadband monocycle vortex generation near 0.6 THz by utilizing a polymeric Tsurupica spiral phase plate in combination with tilted-pulse-front optical rectification in a prism-cut LiNbO3 crystal. A maximum peak power of 2.3 MW was obtained for THz vortex output with an expected topological charge of 1.15. Furthermore, we applied the highly intense THz vortex beam for studying unique nonlinear behaviors in bilayer graphene towards the development of nonlinear super-resolution THz microscopy and imaging system. PMID:27966595

Assessment of swirl spray interaction in lab scale combustor using time-resolved measurements

NASA Astrophysics Data System (ADS)

Rajamanickam, Kuppuraj; Jain, Manish; Basu, Saptarshi

2017-11-01

Liquid fuel injection in highly turbulent swirling flows becomes common practice in gas turbine combustors to improve the flame stabilization. It is well known that the vortex bubble breakdown (VBB) phenomenon in strong swirling jets exhibits complicated flow structures in the spatial domain. In this study, the interaction of hollow cone liquid sheet with such coaxial swirling flow field has been studied experimentally using time-resolved measurements. In particular, much attention is focused towards the near field breakup mechanism (i.e. primary atomization) of liquid sheet. The detailed swirling gas flow field characterization is carried out using time-resolved PIV ( 3.5 kHz). Furthermore, the complicated breakup mechanisms and interaction of the liquid sheet are imaged with the help of high-speed shadow imaging system. Subsequently, proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) is implemented over the instantaneous data sets to retrieve the modal information associated with the interaction dynamics. This helps to delineate more quantitative nature of interaction process between the liquid sheet and swirling gas phase flow field.

Vortex and half-vortex dynamics in a nonlinear spinor quantum fluid

PubMed Central

Dominici, Lorenzo; Dagvadorj, Galbadrakh; Fellows, Jonathan M.; Ballarini, Dario; De Giorgi, Milena; Marchetti, Francesca M.; Piccirillo, Bruno; Marrucci, Lorenzo; Bramati, Alberto; Gigli, Giuseppe; Szymańska, Marzena H.; Sanvitto, Daniele

2015-01-01

Vortices are archetypal objects that recur in the universe across the scale of complexity, from subatomic particles to galaxies and black holes. Their appearance is connected with spontaneous symmetry breaking and phase transitions. In Bose-Einstein condensates and superfluids, vortices are both point-like and quantized quasiparticles. We use a two-dimensional (2D) fluid of polaritons, bosonic particles constituted by hybrid photonic and electronic oscillations, to study quantum vortex dynamics. Polaritons benefit from easiness of wave function phase detection, a spinor nature sustaining half-integer vorticity, strong nonlinearity, and tuning of the background disorder. We can directly generate by resonant pulsed excitations a polariton condensate carrying either a full or half-integer vortex as initial condition and follow their coherent evolution using ultrafast imaging on the picosecond scale. The observations highlight a rich phenomenology, such as the spiraling of the half-vortex and the joint path of the twin charges of a full vortex, until the moment of their splitting. Furthermore, we observe the ordered branching into newly generated secondary couples, associated with the breaking of radial and azimuthal symmetries. This allows us to devise the interplay of nonlinearity and sample disorder in shaping the fluid and driving the vortex dynamics. In addition, our observations suggest that phase singularities may be seen as fundamental particles whose quantized events span from pair creation and recombination to 2D+t topological vortex strings. PMID:26665174

Vortex and half-vortex dynamics in a nonlinear spinor quantum fluid.

PubMed

Dominici, Lorenzo; Dagvadorj, Galbadrakh; Fellows, Jonathan M; Ballarini, Dario; De Giorgi, Milena; Marchetti, Francesca M; Piccirillo, Bruno; Marrucci, Lorenzo; Bramati, Alberto; Gigli, Giuseppe; Szymańska, Marzena H; Sanvitto, Daniele

2015-12-01

Vortices are archetypal objects that recur in the universe across the scale of complexity, from subatomic particles to galaxies and black holes. Their appearance is connected with spontaneous symmetry breaking and phase transitions. In Bose-Einstein condensates and superfluids, vortices are both point-like and quantized quasiparticles. We use a two-dimensional (2D) fluid of polaritons, bosonic particles constituted by hybrid photonic and electronic oscillations, to study quantum vortex dynamics. Polaritons benefit from easiness of wave function phase detection, a spinor nature sustaining half-integer vorticity, strong nonlinearity, and tuning of the background disorder. We can directly generate by resonant pulsed excitations a polariton condensate carrying either a full or half-integer vortex as initial condition and follow their coherent evolution using ultrafast imaging on the picosecond scale. The observations highlight a rich phenomenology, such as the spiraling of the half-vortex and the joint path of the twin charges of a full vortex, until the moment of their splitting. Furthermore, we observe the ordered branching into newly generated secondary couples, associated with the breaking of radial and azimuthal symmetries. This allows us to devise the interplay of nonlinearity and sample disorder in shaping the fluid and driving the vortex dynamics. In addition, our observations suggest that phase singularities may be seen as fundamental particles whose quantized events span from pair creation and recombination to 2D+t topological vortex strings.

Equilibrium vortex structures of type-II/1 superconducting films with washboard pinning landscapes

NASA Astrophysics Data System (ADS)

Wei, C. A.; Xu, X. B.; Xu, X. N.; Wang, Z. H.; Gu, M.

2018-05-01

We numerically study the equilibrium vortex structures of type-II/1 superconducting films with a periodic quasi-one-dimensional corrugated substrate. We show as a function of substrate period and pinning strength that, the vortex system displays a variety of vortex phases including arrays consisted of vortex clumps with different morphologies, ordered vortex stripes parallel and perpendicular to pinning troughs, and ordered one-dimensional vortex chains. Our simulations are helpful in understanding the structural modulations for extensive systems with both competing interactions and competing periodicities.

Size-Induced Depression of First-Order Transition Lines and Entropy Jump in Extremely Layered Nanocrystalline Vortex Matter

NASA Astrophysics Data System (ADS)

Dolz, M. I.; Fasano, Y.; Cejas Bolecek, N. R.; Pastoriza, H.; Mosser, V.; Li, M.; Konczykowski, M.

2015-09-01

We detect the persistence of the solidification and order-disorder first-order transition lines in the phase diagram of nanocrystalline Bi2 Sr2 CaCu2 O8 vortex matter down to a system size of less than one hundred vortices. The temperature location of the vortex solidification transition line is not altered by decreasing the sample size although there is a depletion of the entropy jump at the transition with respect to macroscopic vortex matter. The solid order-disorder phase transition field moves upward on decreasing the system size due to the increase of the surface-to-volume ratio of vortices entailing a decrease on the average vortex binding energy.

Size-Induced Depression of First-Order Transition Lines and Entropy Jump in Extremely Layered Nanocrystalline Vortex Matter.

PubMed

Dolz, M I; Fasano, Y; Cejas Bolecek, N R; Pastoriza, H; Mosser, V; Li, M; Konczykowski, M

2015-09-25

We detect the persistence of the solidification and order-disorder first-order transition lines in the phase diagram of nanocrystalline Bi_{2}Sr_{2}CaCu_{2}O_{8} vortex matter down to a system size of less than one hundred vortices. The temperature location of the vortex solidification transition line is not altered by decreasing the sample size although there is a depletion of the entropy jump at the transition with respect to macroscopic vortex matter. The solid order-disorder phase transition field moves upward on decreasing the system size due to the increase of the surface-to-volume ratio of vortices entailing a decrease on the average vortex binding energy.

Research on aircraft trailing vortex detection based on laser's multiplex information echo

NASA Astrophysics Data System (ADS)

Zhao, Nan-xiang; Wu, Yong-hua; Hu, Yi-hua; Lei, Wu-hu

2010-10-01

Airfoil trailing vortex is an important reason for the crash, and vortex detection is the basic premise for the civil aeronautics boards to make the flight measures and protect civil aviation's security. So a new method of aircraft trailing vortex detection based on laser's multiplex information echo has been proposed in this paper. According to the classical aerodynamics theories, the formation mechanism of the trailing vortex from the airfoil wingtip has been analyzed, and the vortex model of Boeing 737 in the taking-off phase has also been established on the FLUENT software platform. Combining with the unique morphological structure characteristics of trailing vortex, we have discussed the vortex's possible impact on the frequency, amplitude and phase information of laser echo, and expounded the principle of detecting vortex based on fusing this information variation of laser echo. In order to prove the feasibility of this detecting technique, the field experiment of detecting the vortex of civil Boeing 737 by laser has been carried on. The experimental result has shown that the aircraft vortex could be found really in the laser scanning area, and its diffusion characteristic has been very similar to the previous simulation result. Therefore, this vortex detection means based on laser's multiplex information echo was proved to be practicable relatively in this paper. It will provide the detection and identification of aircraft's trailing vortex a new way, and have massive research value and extensive application prospect as well.

Random center vortex lines in continuous 3D space-time

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

Höllwieser, Roman; Institute of Atomic and Subatomic Physics, Vienna University of Technology, Operngasse 9, 1040 Vienna; Altarawneh, Derar

2016-01-22

We present a model of center vortices, represented by closed random lines in continuous 2+1-dimensional space-time. These random lines are modeled as being piece-wise linear and an ensemble is generated by Monte Carlo methods. The physical space in which the vortex lines are defined is a cuboid with periodic boundary conditions. Besides moving, growing and shrinking of the vortex configuration, also reconnections are allowed. Our ensemble therefore contains not a fixed, but a variable number of closed vortex lines. This is expected to be important for realizing the deconfining phase transition. Using the model, we study both vortex percolation andmore » the potential V(R) between quark and anti-quark as a function of distance R at different vortex densities, vortex segment lengths, reconnection conditions and at different temperatures. We have found three deconfinement phase transitions, as a function of density, as a function of vortex segment length, and as a function of temperature. The model reproduces the qualitative features of confinement physics seen in SU(2) Yang-Mills theory.« less

Structured caustic vector vortex optical field: manipulating optical angular momentum flux and polarization rotation.

PubMed

Chen, Rui-Pin; Chen, Zhaozhong; Chew, Khian-Hooi; Li, Pei-Gang; Yu, Zhongliang; Ding, Jianping; He, Sailing

2015-05-29

A caustic vector vortex optical field is experimentally generated and demonstrated by a caustic-based approach. The desired caustic with arbitrary acceleration trajectories, as well as the structured states of polarization (SoP) and vortex orders located in different positions in the field cross-section, is generated by imposing the corresponding spatial phase function in a vector vortex optical field. Our study reveals that different spin and orbital angular momentum flux distributions (including opposite directions) in different positions in the cross-section of a caustic vector vortex optical field can be dynamically managed during propagation by intentionally choosing the initial polarization and vortex topological charges, as a result of the modulation of the caustic phase. We find that the SoP in the field cross-section rotates during propagation due to the existence of the vortex. The unique structured feature of the caustic vector vortex optical field opens the possibility of multi-manipulation of optical angular momentum fluxes and SoP, leading to more complex manipulation of the optical field scenarios. Thus this approach further expands the functionality of an optical system.

Interplay between topological phase and self-acceleration in a vortex symmetric Airy beam.

PubMed

Fang, Zhao-Xiang; Chen, Yue; Ren, Yu-Xuan; Gong, Lei; Lu, Rong-De; Zhang, An-Qi; Zhao, Hong-Ze; Wang, Pei

2018-03-19

Photons in an optical vortex usually carry orbital angular momentum, which boosts the application of the micro-rotation of absorbing particles and quantum information encoding. Such photons propagate along a straight line in free space or follow a curved trace once guided by an optical fiber. Teleportation of an optical vortex using a beam with non-diffraction and self-healing is quite challenging. We demonstrate the manipulation of the propagation trace of an optical vortex with a symmetric Airy beam (SAB) and found that the SAB experiences self-rotation with the implementation of a topological phase structure of coaxial vortex. Slight misalignment of the vortex and the SAB enables the guiding of the vortex into one of the self-accelerating channels. Multiple off-axis vortices embedded in SAB are also demonstrated to follow the trajectory of the major lobe for the SAB beam. The Poynting vector for the beams proves the direction of the energy flow corresponding to the intensity distribution. Hence, we anticipate that the proposed vortex symmetric Airy beam (VSAB) will provide new possibilities for optical manipulation and optical communication.

Vectorial diffraction properties of THz vortex Bessel beams.

PubMed

Wu, Zhen; Wang, Xinke; Sun, Wenfeng; Feng, Shengfei; Han, Peng; Ye, Jiasheng; Yu, Yue; Zhang, Yan

2018-01-22

A vortex Bessel beam combines the merits of an optical vortex and a Bessel beam, including a spiral wave front and a non-diffractive feature, which has immense application potentials in optical trapping, optical fabrication, optical communications, and so on. Here, linearly and circularly polarized vortex Bessel beams in the terahertz (THz) frequency range are generated by utilizing a THz quarter wave plate, a spiral phase plate, and Teflon axicons with different opening angles. Taking advantage of a THz focal-plane imaging system, vectorial diffraction properties of the THz vortex Bessel beams are comprehensively characterized and discussed, including the transverse (Ex, Ey) and longitudinal (Ez) polarization components. The experimental phenomena are accurately simulated by adopting the vectorial Rayleigh diffraction integral. By varying the opening angle of the axicon, the characteristic parameters of these THz vortex Bessel beams are exhibited and compared, including the light spot size, the diffraction-free range, and the phase evolution process. This work provides the precise experimental and theoretical bases for the comprehension and application of a THz vortex Bessel beam.

Ultrasound assisted extraction combined with dispersive liquid-liquid microextraction (US-DLLME)-a fast new approach to measure phthalate metabolites in nails.

PubMed

Alves, Andreia; Vanermen, Guido; Covaci, Adrian; Voorspoels, Stefan

2016-09-01

A new, fast, and environmentally friendly method based on ultrasound assisted extraction combined with dispersive liquid-liquid microextraction (US-DLLME) was developed and optimized for assessing the levels of seven phthalate metabolites (including the mono(ethyl hexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (5-OH-MEHP), mono(2-ethyl-5-oxohexyl) phthalate (5-oxo-MEHP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), monoethyl phthalate (MEP), and mono-benzyl phthalate (MBzP)) in human nails by UPLC-MS/MS. The optimization of the US-DLLME method was performed using a Taguchi combinatorial design (L9 array). Several parameters such as extraction solvent, solvent volume, extraction time, acid, acid concentration, and vortex time were studied. The optimal extraction conditions achieved were 180 μL of trichloroethylene (extraction solvent), 2 mL trifluoroacetic acid in methanol (2 M), 2 h extraction and 3 min vortex time. The optimized method had a good precision (6-17 %). The accuracy ranged from 79 to 108 % and the limit of method quantification (LOQm) was below 14 ng/g for all compounds. The developed US-DLLME method was applied to determine the target metabolites in 10 Belgian individuals. Levels of the analytes measured in nails ranged between <12 and 7982 ng/g. The MEHP, MBP isomers, and MEP were the major metabolites and detected in every sample. Miniaturization (low volumes of organic solvents used), low costs, speed, and simplicity are the main advantages of this US-DLLME based method. Graphical Abstract Extraction and phase separation of the US-DLLME procedure.

Multiple orbital angular momentum generated by dielectric hybrid phase element

NASA Astrophysics Data System (ADS)

Wang, Xuewen; Kuchmizhak, Aleksandr; Hu, Dejiao; Li, Xiangping

2017-09-01

Vortex beam carrying multiple orbital angular momentum provides a new degree of freedom to manipulate light leading to the various exciting applications as trapping, quantum optics, information multiplexing, etc. Helical wavefront can be generated either via the geometric or the dynamic phase arising from a space-variant birefringence (q-plate) or from phase accumulation through propagation (spiral-phase-plate), respectively. Using fast direct laser writing technique we fabricate and characterize novel hybrid q-plate generating vortex beam simultaneously carrying two different high-order topological charges, which arise from the spin-orbital conversion and the azimuthal height variation of the recorded structures. We approve the versatile concept to generate multiple-OAM vortex beams combining the spin-orbital interaction and the phase accumulation in a single micro-scale device, a hybrid dielectric phase plate.

Phase locking of vortex cores in two coupled magnetic nanopillars

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

Zhu, Qiyuan; Liu, Xianyin; Zheng, Qi

2014-11-15

Phase locking dynamics of the coupled vortex cores in two identical magnetic spin valves induced by spin-polarized current are studied by means of micromagnetic simulations. Our results show that the available current range of phase locking can be expanded significantly by the use of constrained polarizer, and the vortices undergo large orbit motions outside the polarization areas. The effects of polarization areas and dipolar interaction on the phase locking dynamics are studied systematically. Phase locking parameters extracted from simulations are discussed by theoreticians. The dynamics of vortices influenced by spin valve geometry and vortex chirality are discussed at last. Thismore » work provides deeper insights into the dynamics of phase locking and the results are important for the design of spin-torque nano-oscillators.« less

Disappearance of the force-free current configuration at the first order vortex lattice phase transition in YBa 2Cu 3O 7-δ single crystals

NASA Astrophysics Data System (ADS)

van der Beek, C. J.; Indenbom, M. V.; Berseth, V.; Benoit, W.; Erb, A.; Flükiger, R.

1997-08-01

The anisotropy in the transverse AC susceptibility of YBa2Cu3O7-δ single crystals, induced by the periodic appearance of a force-free current configuration upon rotation of a superimposed DC field in the crystal plane, disappears at the vortex phase transition, indicating the loss of the vortex lines' stability against mutual cutting.

An Organic Vortex Laser.

PubMed

Stellinga, Daan; Pietrzyk, Monika E; Glackin, James M E; Wang, Yue; Bansal, Ashu K; Turnbull, Graham A; Dholakia, Kishan; Samuel, Ifor D W; Krauss, Thomas F

2018-03-27

Optical vortex beams are at the heart of a number of novel research directions, both as carriers of information and for the investigation of optical activity and chiral molecules. Optical vortex beams are beams of light with a helical wavefront and associated orbital angular momentum. They are typically generated using bulk optics methods or by a passive element such as a forked grating or a metasurface to imprint the required phase distribution onto an incident beam. Since many applications benefit from further miniaturization, a more integrated yet scalable method is highly desirable. Here, we demonstrate the generation of an azimuthally polarized vortex beam directly by an organic semiconductor laser that meets these requirements. The organic vortex laser uses a spiral grating as a feedback element that gives control over phase, handedness, and degree of helicity of the emitted beam. We demonstrate vortex beams up to an azimuthal index l = 3 that can be readily multiplexed into an array configuration.

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

Lee, Ji San; Park, Su Ji; Lee, Jun Ho

A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row ofmore » vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.« less

Vortex Formation and Acceleration of a Fish-Inspired Robot Performing Starts from Rest

NASA Astrophysics Data System (ADS)

Devoria, Adam; Bapst, Jonathan; Ringuette, Matthew

2009-11-01

We investigate the unsteady flow of a fish-inspired robot executing starts from rest, with the objective of understanding the connection among the kinematics, vortex formation, and acceleration performance. Several fish perform ``fast starts,'' where the body bends into a ``C'' or ``S'' shape while turning (phase I), followed by a straightening of the body and caudal fin and a linear acceleration (phase II). The resulting highly 3-D, unsteady vortex formation and its relationship to the acceleration are not well understood. The self-propelled robotic model contains motor-driven joints with programmable motion to emulate phase II of a simplified C-start. The experiments are conducted in a water tank, and the model is constrained to 1 direction along rails. The velocity is measured using digital particle image velocimetry (DPIV) in multiple planes. Vortex boundaries are identified using the finite-time Lyapunov exponent, then the unsteady vortex circulation is computed. The thrust is estimated from the identified vortices, and correlated with the circulation and model acceleration for different kinematics.

A Carbon Dioxide Bubble-Induced Vortex Triggers Co-Assembly of Nanotubes with Controlled Chirality.

PubMed

Zhang, Ling; Zhou, Laicheng; Xu, Na; Ouyang, Zhenjie

2017-07-03

It is challenging to prepare co-organized nanotube systems with controlled nanoscale chirality in an aqueous liquid flow field. Such systems are responsive to a bubbled external gas. A liquid vortex induced by bubbling carbon dioxide (CO 2 ) gas was used to stimulate the formation of nanotubes with controlled chirality; two kinds of achiral cationic building blocks were co-assembled in aqueous solution. CO 2 -triggered nanotube formation occurs by formation of metastable intermediate structures (short helical ribbons and short tubules) and by transition from short tubules to long tubules in response to chirality matching self-assembly. Interestingly, the chirality sign of these assemblies can be selected for by the circulation direction of the CO 2 bubble-induced vortex during the co-assembly process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of vortex-assisted MSPD and LC-MS/MS using alternative solid supports for pharmaceutical extraction from marketed fish.

PubMed

Hertzog, Gabriel I; Soares, Karina L; Caldas, Sergiane S; Primel, Ednei G

2015-06-01

A procedure based on vortex-assisted matrix solid-phase dispersion (MSPD) for the extraction of 15 pharmaceuticals from fish samples with determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was validated. Florisil, C18, diatomaceous earth, chitin, and chitosan were evaluated as solid supports. Best results were obtained with 0.5 g of diatomaceous earth, 0.5 g of sodium sulfate, and 5 mL of methanol. Analytical recoveries ranged from 58 to 128 % with relative standard deviation (RSD) lower than 15 %. Limit of quantification (LOQ) values for the 15 compounds ranged from 5 to 1000 ng g(-1). The method under investigation has shown to be a simple and fast extraction tool with minimum instrumentation and low amount of reagent, resulting in method low cost. Besides, alternative materials, such as chitin and chitosan, which were applied to the dispersion step for the first time, were found to be interesting alternatives.

Determination of alternative preservatives in cosmetic products by chromophoric derivatization followed by vortex-assisted liquid-liquid semimicroextraction and liquid chromatography.

PubMed

Miralles, Pablo; Vrouvaki, Ilianna; Chisvert, Alberto; Salvador, Amparo

2016-07-01

An analytical method for the simultaneous determination of phenethyl alcohol, methylpropanediol, phenylpropanol, caprylyl glycol, and ethylhexylglycerin, which are used as alternative preservatives in cosmetic products, has been developed. The method is based on liquid chromatography with UV spectrophotometric detection after chromophoric derivatization with benzoyl chloride and vortex-assisted liquid-liquid semimicroextraction. Different chromatographic parameters, derivatization conditions, and sample preparation variables were studied. Under optimized conditions, the limits of detection values for the analytes ranged from 0.02 to 0.06µgmL(-1). The method was validated with good recovery values (84-118%) and precision values (3.9-9.5%). It was successfully applied to 10 commercially available cosmetic samples. The good analytical features of the proposed method besides of its environmentally-friendly characteristics, make it useful to carry out the quality control of cosmetic products containing the target compounds as preservative agents. Copyright © 2016 Elsevier B.V. All rights reserved.

Demonstration of a terahertz pure vector beam by tailoring geometric phase.

PubMed

Wakayama, Toshitaka; Higashiguchi, Takeshi; Sakaue, Kazuyuki; Washio, Masakazu; Otani, Yukitoshi

2018-06-06

We demonstrate the creation of a vector beam by tailoring geometric phase of left- and right- circularly polarized beams. Such a vector beam with a uniform phase has not been demonstrated before because a vortex phase remains in the beam. We focus on vortex phase cancellation to generate vector beams in terahertz regions, and measure the geometric phase of the beam and its spatial distribution of polarization. We conduct proof-of-principle experiments for producing a vector beam with radial polarization and uniform phase at 0.36 THz. We determine the vortex phase of the vector beam to be below 4%, thus highlighting the extendibility and availability of the proposed concept to the super broadband spectral region from ultraviolet to terahertz. The extended range of our proposed techniques could lead to breakthroughs in the fields of microscopy, chiral nano-materials, and quantum information science.

Combined dispersive solid-phase extraction-dispersive liquid-liquid microextraction-derivatization for gas chromatography-mass spectrometric determination of aliphatic amines on atmospheric fine particles.

PubMed

Majedi, Seyed Mohammad; Lee, Hian Kee

2017-02-24

Short-chain aliphatic amines are ubiquitous in the atmospheric environment. They play an important role in the formation and growth of atmospheric particles. As such, there is a pressing need to monitor these particle-bound compounds present at trace quantities. The present work describes an efficient, one-step microextraction technique for the preconcentration and detection of trace levels of 10 aliphatic amines on fine particles (particulate matter of 2.5μm or less (PM 2.5 )) in the atmosphere. After extraction of amines from particles in acidified water samples, carbon-based sorbents (in dispersive solid-phase extraction mode), and vortex agitation were utilized for simultaneous derivatization-extraction and dispersive liquid-liquid microextraction. The approach significantly increased the recoveries and enrichment of the amine derivatives. This one-step, combined technique is proposed for the first time. Several influential factors including type and concentration of derivatization reagent (for gas chromatographic separation), type of buffer, sample pH, types and volumes of extraction and disperser solvents, type and amount of sorbent, vortex time and temperature, desorption solvent type and volume, and salt content were investigated and optimized. Under the optimum conditions, high enrichment factors (in the range of between 307 and 382) and good reproducibility (relative standard deviations, below 7.0%, n=5) were achieved. The linearity ranged from 0.1μg/L-100μg/L, and from 0.5μg/L-100μg/L, depending on the analytes. The limits of detection were between 0.02μg/L (corresponding to ∼0.01ng/m 3 in air) and 0.09μg/L (corresponding to ∼0.04ng/m 3 in air). The developed method was successfully applied to the analysis of PM 2.5 samples collected by air sampling through polytetrafluoroethylene filters. The concentration levels of amines ranged from 1.04 to 4.16ng/m 3 in the air sampled. Copyright © 2016 Elsevier B.V. All rights reserved.

The physics of transverse mode instability-induced nonlinear phase distortions in large area optical fiber amplifiers and their mitigation with applications in scaling of pulsed and continuous wave high-energy lasers

DTIC Science & Technology

2016-12-13

plate and novel all-fiber fused coupler. Such work has laid the platform to demonstrate the mitigation of thermal mode instability through vortex beam...at IIT Madras to experimentally validate the above results as well as to explore the generation of vortex modes through a spiral phase plate and...modes through spiral phase plates and novel all-fiber fused couplers. We have demonstrated the excitation of a vortex mode with charge 1 through a

Topological charge algebra of optical vortices in nonlinear interactions.

PubMed

Zhdanova, Alexandra A; Shutova, Mariia; Bahari, Aysan; Zhi, Miaochan; Sokolov, Alexei V

2015-12-28

We investigate the transfer of orbital angular momentum among multiple beams involved in a coherent Raman interaction. We use a liquid crystal light modulator to shape pump and Stokes beams into optical vortices with various integer values of topological charge, and cross them in a Raman-active crystal to produce multiple Stokes and anti-Stokes sidebands. We measure the resultant vortex charges using a tilted-lens technique. We verify that in every case the generated beams' topological charges obey a simple relationship, resulting from angular momentum conservation for created and annihilated photons, or equivalently, from phase-matching considerations for multiple interacting beams.

Optical and physical requirements for fluid particles marking trailing vortices from aircraft

NASA Technical Reports Server (NTRS)

Back, L. H.

1976-01-01

A theoretical study of the optical and physical requirements of marking trailing vortices that emanate from aircraft wings was carried out by considering particulate light-scattering properties, ability of particles to follow trailing vortices, and survival time of particles to vortex dissipation. Liquid droplets undergoing evaporation and molecular dispersion were investigated. Droplets should have lifetimes of about 300 sec. Droplet size should be about 1 micron to maximize light scattering with the minimum mass of liquid required. Droplets of this small size would spiral outward very slowly and essentially remain in the vortex cores. Nontoxic hygroscopic liquids, having an affinity for moisture in the air, have been identified. These liquids have relatively low vapor pressures of order 10 to the -5 mm Hg that would insure droplet persistence long enough to mark trailing vortices.

Holographic optical tweezers for object manipulations at an air-liquid surface.

PubMed

Jesacher, Alexander; Fürhapter, Severin; Maurer, Christian; Bernet, Stefan; Ritsch-Marte, Monika

2006-06-26

We investigate holographic optical tweezers manipulating micro-beads at a suspended air-liquid interface. Axial confinement of the particles in the two-dimensional interface is maintained by the interplay between surface tension and gravity. Therefore, optical trapping of the micro-beads is possible even with a long distance air objective. Efficient micro-circulation of the liquid can be induced by fast rotating beads, driven by the orbital angular momentum transfer of incident Laguerre-Gaussian (doughnut) laser modes. Our setup allows various ways of creating a tailored dynamic flow of particles and liquid within the surface. We demonstrate examples of surface manipulations like efficient vortex pumps and mixers, interactive particle flow steering by arrays of vortex pumps, the feasibility of achieving a "clocked" traffic of micro beads, and size-selective guiding of beads along optical "conveyor belts".

Three-Phased Wake Vortex Decay

NASA Technical Reports Server (NTRS)

Proctor, Fred H.; Ahmad, Nashat N.; Switzer, George S.; LimonDuparcmeur, Fanny M.

2010-01-01

A detailed parametric study is conducted that examines vortex decay within turbulent and stratified atmospheres. The study uses a large eddy simulation model to simulate the out-of-ground effect behavior of wake vortices due to their interaction with atmospheric turbulence and thermal stratification. This paper presents results from a parametric investigation and suggests improvements for existing fast-time wake prediction models. This paper also describes a three-phased decay for wake vortices. The third phase is characterized by a relatively slow rate of circulation decay, and is associated with the ringvortex stage that occurs following vortex linking. The three-phased decay is most prevalent for wakes imbedded within environments having low-turbulence and near-neutral stratification.

The Effect of the Air-Delivery Method on Parameters of the Precessing Vortex Core in a Hydrodynamic Vortex Chamber

NASA Astrophysics Data System (ADS)

Alekseenko, S. V.; Shtork, S. I.; Yusupov, R. R.

2018-03-01

The effect of the method of gas-phase injection into a swirled fluid flow on parameters of a precessing vortex core is studied experimentally. Conditions of the appearance of the vortex-core precession effect were modeled in a hydrodynamic sudden expansion vortex chamber. The dependences of the vortexcore precession frequency, flow-pulsation level, and full pressure differential in the vortex chamber on the consumption gas content in the flow have been obtained. The results of measurements permit one to determine optimum conditions for the most effective control of vortex-core precession.

Vector vortex beam generation with dolphin-shaped cell meta-surface.

PubMed

Yang, Zhuo; Kuang, Deng-Feng; Cheng, Fang

2017-09-18

We present a dolphin-shaped cell meta-surface, which is a combination of dolphin-shaped metallic cells and dielectric substrate, for vector vortex beam generation with the illumination of linearly polarized light. Surface plasmon polaritons are excited at the boundary of the metallic cells, then guided by the metallic structures, and finally squeezed to the tips to form highly localized strong electromagnetic fields, which generate the intensity of vector vortex beams at z component. Synchronously, the abrupt phase change produced by the meta-surface is utilized to explain the vortex phase generated by elements. The new kind of structure can be utilized for communication, bioscience, and materiality.

ProFile Vortex and Vortex Blue Nickel-Titanium Rotary Instruments after Clinical Use.

PubMed

Shen, Ya; Zhou, Huimin; Coil, Jeffrey M; Aljazaeri, Bassim; Buttar, Rene; Wang, Zhejun; Zheng, Yu-feng; Haapasalo, Markus

2015-06-01

The aim of this study was to analyze the incidence and mode of ProFile Vortex and Vortex Blue instrument defects after clinical use in a graduate endodontic program and to examine the impact of clinical use on the instruments' metallurgical properties. A total of 330 ProFile Vortex and 1136 Vortex Blue instruments from the graduate program were collected after each had been used in 3 teeth. The incidence and type of instrument defects were analyzed. The lateral surfaces and fracture surfaces of the fractured files were examined by using scanning electron microscopy. Unused and used instruments were examined by full and partial differential scanning calorimetry. No fractures were observed in the 330 ProFile Vortex instruments, whereas 20 (6.1%) revealed bent or blunt defects. Only 2 of the 1136 Vortex Blue files fractured during clinical use. The cause of fracture was shear stress. The fractures occurred at the tip end of the spirals. Only 1.8% (21 of 1136) of the Vortex Blue files had blunt tips. Austenite-finish temperatures were very similar for unused and used ProFile Vortex files and were all greater than 50°C. The austenite-finish temperatures of used and unused Vortex Blue files (38.5°C) were lower than those in ProFile Vortex instruments (P < .001). However, the transformation behavior of Vortex Blue files had an obvious 2-stage transformation, martensite-to-R phase and R-to-austenite phase. The trends of differential scanning calorimetry plots of unused Vortex Blue instruments and clinically used instruments were very similar. The risk of ProFile Vortex and Vortex Blue instrument fracture is very low when instruments are discarded after clinical use in the graduate endodontic program. The Vortex Blue files have metallurgical behavior different from ProFile Vortex instruments. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Glycoalkaloid content in pet food by UPLC-tandem mass spectrometry.

PubMed

Sheridan, Robert S; Kemnah, Jennifer L

2010-11-01

The glycoalkaloid content of pet food containing potatoes is investigated using a liquid-liquid solvent extraction followed by analysis by ultra-high pressure liquid chromatography tandem mass spectrometry (UPLC-MS-MS). Pet food samples are homogenized and extracted with a solution of 50:50 (v/v) acetonitrile-deionized water containing 5% acetic acid. Following vortexing and centrifugation, 3 mL of the supernatant is filtered and diluted in deionized water. The extract is injected onto a reverse phase C18 UPLC column with an initial mobile phase composed of 0.15% acetic acid in water (A) and 0.15% acetic acid in methanol (B) in a ratio of 70:30, respectively. The mobile phase reaches a final concentration of 15% A and 85% B over 10 min, at which point it is returned to the initial conditions. α-Solanine is measured by monitoring transitions m/z = 868.50 → 398.40 and 868.50 → 722.50, while α-chaconine is measure by monitoring transitions m/z = 852.60 → 97.80 and 852.60 → 706.50. Each analyte is measured and combined to determine total glycoalkaloid content (TGA). The results of the analysis of 52 pet food samples indicate both glycoalkaloids are present in all samples and two pet foods were found to contain > 100 μg/g total glycoalkaloid.

Deep eutectic solvent based gas-assisted dispersive liquid-phase microextraction combined with gas chromatography and flame ionization detection for the determination of some pesticide residues in fruit and vegetable samples.

PubMed

Farajzadeh, Mir Ali; Sattari Dabbagh, Masoumeh; Yadeghari, Adeleh

2017-05-01

In this study, a gas-assisted dispersive liquid-phase microextraction method using a deep eutectic solvent as the extraction solvent combined with gas chromatography and flame ionization detection was developed for the extraction and determination of some pesticide residues in vegetable and fruit juice samples. In this method, choline chloride and 4-chlorophenol at a molar ratio of 1:2 were mixed. By heating and vortexing, a clear, water-immiscible, and homogeneous liquid was formed. The obtained deep eutectic solvent was added to an aqueous solution of the analytes in a conical test tube. Air was bubbled into the aqueous solution and a cloudy solution was obtained. During this step, the analytes were extracted into the fine droplets of the extraction solvent. After centrifugation, an aliquot of the settled phase was injected into the separation system. Under the optimum extraction conditions, enrichment factors, and extraction recoveries were obtained in the ranges of 247-355 and 49-71%, respectively. The obtained values for the limits of detection and quantification were in the ranges of 0.24-1.4 and 0.71-4.2 μg/L, respectively. The proposed method is simple, fast, efficient, and inexpensive. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generation and characterization of a perfect vortex beam with a large topological charge through a digital micromirror device.

PubMed

Chen, Yue; Fang, Zhao-Xiang; Ren, Yu-Xuan; Gong, Lei; Lu, Rong-De

2015-09-20

Optical vortices are associated with a spatial phase singularity. Such a beam with a vortex is valuable in optical microscopy, hyper-entanglement, and optical levitation. In these applications, vortex beams with a perfect circle shape and a large topological charge are highly desirable. But the generation of perfect vortices with high topological charges is challenging. We present a novel method to create perfect vortex beams with large topological charges using a digital micromirror device (DMD) through binary amplitude modulation and a narrow Gaussian approximation. The DMD with binary holograms encoding both the spatial amplitude and the phase could generate fast switchable, reconfigurable optical vortex beams with significantly high quality and fidelity. With either the binary Lee hologram or the superpixel binary encoding technique, we were able to generate the corresponding hologram with high fidelity and create a perfect vortex with topological charge as large as 90. The physical properties of the perfect vortex beam produced were characterized through measurements of propagation dynamics and the focusing fields. The measurements show good consistency with the theoretical simulation. The perfect vortex beam produced satisfies high-demand utilization in optical manipulation and control, momentum transfer, quantum computing, and biophotonics.

NUMERICAL SIMULATIONS OF KELVIN–HELMHOLTZ INSTABILITY: A TWO-DIMENSIONAL PARAMETRIC STUDY

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

Tian, Chunlin; Chen, Yao, E-mail: chunlin.tian@sdu.edu.cn

2016-06-10

Using two-dimensional simulations, we numerically explore the dependences of Kelvin–Helmholtz (KH) instability upon various physical parameters, including viscosity, the width of the sheared layer, flow speed, and magnetic field strength. In most cases, a multi-vortex phase exists between the initial growth phase and the final single-vortex phase. The parametric study shows that the evolutionary properties, such as phase duration and vortex dynamics, are generally sensitive to these parameters, except in certain regimes. An interesting result is that for supersonic flows, the phase durations and saturation of velocity growth approach constant values asymptotically as the sonic Mach number increases. We confirmmore » that the linear coupling between magnetic field and KH modes is negligible if the magnetic field is weak enough. The morphological behavior suggests that the multi-vortex coalescence might be driven by the underlying wave–wave interaction. Based on these results, we present a preliminary discussion of several events observed in the solar corona. The numerical models need to be further improved to perform a practical diagnostic of the coronal plasma properties.« less

Vortex Ring Interaction with a Heated Screen

NASA Astrophysics Data System (ADS)

Smith, Jason; Krueger, Paul S.

2008-11-01

Previous examinations of vortex rings impinging on porous screens has shown the reformation of the vortex ring with a lower velocity after passing through the screen, the creation of secondary vortices, and mixing. A heated screen could, in principle, alter the vortex-screen interaction by changing the local liquid viscosity and density. In the present investigation, a mechanical piston-cylinder vortex ring generator was used to create vortex rings in an aqueous sucrose solution. The rings impinged on a screen of horizontal wires that were heated using electrical current. The flow was visualized with food color and video imaging. Tests with and without heat were conducted at a piston stroke-to-jet diameter ratio of 4 and a jet Reynolds number (Re) of 1000. The vortex rings slowed after passing through the screen, but in tests with heat, they maintained a higher fraction of their before-screen velocity due to reduction in fluid viscosity near the wires. In addition, small ``fingers'' that developed on the front of the vortex rings as they passed through the screen exhibited positive buoyancy effects in the heated case.

Model of random center vortex lines in continuous 2 +1 -dimensional spacetime

NASA Astrophysics Data System (ADS)

Altarawneh, Derar; Engelhardt, Michael; Höllwieser, Roman

2016-12-01

A picture of confinement in QCD based on a condensate of thick vortices with fluxes in the center of the gauge group (center vortices) is studied. Previous concrete model realizations of this picture utilized a hypercubic space-time scaffolding, which, together with many advantages, also has some disadvantages, e.g., in the treatment of vortex topological charge. In the present work, we explore a center vortex model which does not rely on such a scaffolding. Vortices are represented by closed random lines in continuous 2 +1 -dimensional space-time. These random lines are modeled as being piecewise linear, and an ensemble is generated by Monte Carlo methods. The physical space in which the vortex lines are defined is a torus with periodic boundary conditions. Besides moving, growing, and shrinking of the vortex configurations, also reconnections are allowed. Our ensemble therefore contains not a fixed but a variable number of closed vortex lines. This is expected to be important for realizing the deconfining phase transition. We study both vortex percolation and the potential V (R ) between the quark and antiquark as a function of distance R at different vortex densities, vortex segment lengths, reconnection conditions, and at different temperatures. We find three deconfinement phase transitions, as a function of density, as a function of vortex segment length, and as a function of temperature.

The modified swirl sedimentation tanks for water purification.

PubMed

Ochowiak, Marek; Matuszak, Magdalena; Włodarczak, Sylwia; Ancukiewicz, Małgorzata; Krupińska, Andżelika

2017-03-15

This paper discusses design, evaluation, and application for the use of swirl/vortex technologies as liquid purification system. A study was performed using modified swirl sedimentation tanks. The vortex separators (OW, OWK, OWR and OWKR) have been studied under laboratory conditions at liquid flow rate from 2.8⋅10 -5 to 5.1⋅10 -4 [m 3 /s]. The pressure drop and the efficiency of purification of liquid stream were analyzed. The suspended particles of different diameters were successfully removed from liquid with the application of swirl chambers of proposed constructions. It was found that damming of liquid in the tank increases alongside liquid stream at the inlet and depends on the tank construction. The efficiency of the sedimentation tanks increases alongside the diameters of solid particles and decrease in the liquid flow rate. The best construction proved to be the OWR sedimentation tank due to smallest liquid damming, even at high flow rates, and the highest efficiency of the purification liquid stream for solid particles of the smallest diameter. The proposed solution is an alternative to the classical constructions of sedimentation tanks. Copyright © 2016 Elsevier Ltd. All rights reserved.

Efficient Nonlinear Atomization Model for Thin 3D Free Liquid Films

NASA Astrophysics Data System (ADS)

Mehring, Carsten

2007-03-01

Reviewed is a nonlinear reduced-dimension thin-film model developed by the author and aimed at the prediction of spray formation from thin films such as those found in gas-turbine engines (e.g., prefilming air-blast atomizers), heavy-fuel-oil burners (e.g., rotary-cup atomizers) and in the paint industry (e.g., flat-fan atomizers). Various implementations of the model focusing on different model-aspects, i.e., effect of film geometry, surface tension, liquid viscosity, coupling with surrounding gas-phase flow, influence of long-range intermolecular forces during film rupture are reviewed together with a validation of the nonlinear wave propagation characteristics predicted by the model for inviscid planar films using a two-dimensional vortex- method. An extension and generalization of the current nonlinear film model for implementation into a commercial flow- solver is outlined.

Ultrashort vortex from a Gaussian pulse - An achromatic-interferometric approach.

PubMed

Naik, Dinesh N; Saad, Nabil A; Rao, D Narayana; Viswanathan, Nirmal K

2017-05-24

The more than a century old Sagnac interferometer is put to first of its kind use to generate an achromatic single-charge vortex equivalent to a Laguerre-Gaussian beam possessing orbital angular momentum (OAM). The interference of counter-propagating polychromatic Gaussian beams of beam waist ω λ with correlated linear phase (ϕ 0  ≥ 0.025 λ) and lateral shear (y 0  ≥ 0.05 ω λ ) in orthogonal directions is shown to create a vortex phase distribution around the null interference. Using a wavelength-tunable continuous-wave laser the entire range of visible wavelengths is shown to satisfy the condition for vortex generation to achieve a highly stable white-light vortex with excellent propagation integrity. The application capablitiy of the proposed scheme is demonstrated by generating ultrashort optical vortex pulses, its nonlinear frequency conversion and transforming them to vector pulses. We believe that our scheme for generating robust achromatic vortex (implemented with only mirrors and a beam-splitter) pulses in the femtosecond regime, with no conceivable spectral-temporal range and peak-power limitations, can have significant advantages for a variety of applications.

Frequency characteristics of liquid hydrogen cavitating flow over a NACA0015 hydrofoil

NASA Astrophysics Data System (ADS)

Zhu, Jiakai; Wang, Shunhao; Qiu, Limin; Zhi, Xiaoqin; Zhang, Xiaobin

2018-03-01

Large eddy simulation on unsteady cavitating flow of liquid hydrogen over a three-dimensional NACA0015 hydrofoil with the attack angle (α) of 6° are carried out to investigate the dynamic features of cavity with the existence of thermal effects. The numerical model considers the compressibility of both liquid and vapor phase, and is validated by comparing the results with the available experimental data. Special emphasis is put on analyzing the frequency characteristics of cavitation cloud. Strouhal number (St) is plotted against σ/2α (σ is cavitation number), and the water cavitation data reported by Andrt et al. are also used as a reference. It is found that the St number for LH2 cavitation is much smaller than the water, in which the thermal effects are generally not considered, at the same σ/2α value when it is greater than about 2.0, while it returns to the same level as water when σ/2α decreases to below 2.0. The reason is primarily ascribed to the thermal effects, and the detailed explanations are given based on the recognitions that the shedding mechanism of cavitation clouds is predominated by the combined action of the vortex flow and thermal effects. While, when σ/2α decreases to a critical value, the relative effect of the thermal effects on the cavitation dynamics is greatly weakened compared with the mechanism due to the vortex flow, like those in isothermal cavitation flow in traditional fluids. The results provide a deeper understanding of the cryogenic fluid cavitation flow.

Partially filled Landau level at even denominators: A vortex metal with a Berry phase

NASA Astrophysics Data System (ADS)

You, Yizhi

2018-04-01

We develop a vortex metal theory for a partially filled Landau level at ν =1/2 n whose ground state contains a composite Fermi surface formed by the vortex of electrons. In the projected Landau-level limit, the composite Fermi surface contains a -π/n Berry phase. Such a fractional Berry phase is a consequence of Landau-level projection which produces the Girvin-MacDonald-Platzman [S. M. Girvin, A. H. MacDonald, and P. M. Platzman, Phys. Rev. B 33, 2481 (1986), 10.1103/PhysRevB.33.2481] guiding center algebra and embellishes an anomalous velocity to the equation of motion for the vortex metal. Further, we investigate a particle-hole symmetric bilayer system with ν1=1/2 n and ν2=1 -1/2 n at each layer, and demonstrate that the -π/n Berry phase on the composite Fermi surface leads to the suppression of 2 kf backscattering between the particle-hole partner bilayer, which could be a smoking gun to detect the fractional Berry phase. We also mention various instabilities and competing orders in such bilayer systems, including a Z4 n topological order phase driven by quantum criticality.

Beam shaping with vectorial vortex beams under low numerical aperture illumination condition

NASA Astrophysics Data System (ADS)

Dai, Jianning; Zhan, Qiwen

2008-08-01

In this paper we propose and demonstrate a novel beam shaping method using vectorial vortex beam. A vectorial vortex beam is laser beam with polarization singularity in the beam cross section. This type of beams can be decomposed into two orthogonally polarized components. Each of the polarized components could have different vortex characteristics, and consequently, different intensity distribution when focused by lens. Beam shaping in the far field can be achieved by adjusting the relative weighing of these two components. As one example, we study the vectorial vortex that consists of a linearly polarized Gaussian component and a vortex component polarized orthogonally. When such a vectorial vortex beam is focus by low NA lens, the Gaussian component gives rise to a focal intensity distribution with a solid centre while the vortex component gives rise to a donut distribution with hollow dark center. The shape of the focus can be continuously varied by continuously adjusting the relative weight of the two components. Under appropriate conditions, flat top focusing can be obtained. We experimentally demonstrate the creation of such beams with a liquid crystal spatial light modulator. Flattop focus obtained by vectorial vortex beams with topological charge of +1 has been obtained.

Simulation and phases of macroscopic particles in vortex flow

NASA Astrophysics Data System (ADS)

Rice, Heath Eric

Granular materials are an interesting class of media in that they exhibit many disparate characteristics depending on conditions. The same set of particles may behave like a solid, liquid, gas, something in-between, or something completely unique depending on the conditions. Practically speaking, granular materials are used in many aspects of manufacturing, therefore any new information gleaned about them may help refine these techniques. For example, learning of a possible instability may help avoid it in practical application, saving machinery, money, and even personnel. To that end, we intend to simulate a granular medium under tornado-like vortex airflow by varying particle parameters and observing the behaviors that arise. The simulation itself was written in Python from the ground up, starting from the basic simulation equations in Poschel [1]. From there, particle spin, viscous friction, and vertical and tangential airflow were added. The simulations were then run in batches on a local cluster computer, varying the parameters of radius, flow force, density, and friction. Phase plots were created after observing the behaviors of the simulations and the regions and borders were analyzed. Most of the results were as expected: smaller particles behaved more like a gas, larger particles behaved more like a solid, and most intermediate simulations behaved like a liquid. A small subset formed an interesting crossover region in the center, and under moderate forces began to throw a few particles at a time upward from the center in a fountain-like effect. Most borders between regions appeared to agree with analysis, following a parabolic critical rotational velocity at which the parabolic surface of the material dips to the bottom of the mass of particles. The fountain effects seemed to occur at speeds along and slightly faster than this division. [1] Please see thesis for references.

Detection of Second Order Melting Transitions in the HTSC's by Specific Heat Measurements?

NASA Astrophysics Data System (ADS)

Pierson, Stephen W.; Valls, Oriol T.

1997-03-01

The finite magnetic field phase transition in the high-temperature superconductors from the solid vortex lattice to the liquid has been under intense study recently. Detection of this melting is difficult but has been seen in magnetization and resistivity measurements. It has also been reported recently in specific heat measurements. In particular, in one case, evidence for a second order melting phase transition has been presented based on specific heat measurements.(M. Roulin, A. Junod, and E. Walker. Science 273), 1210 (1996). However, we present evidence that the feature in the specific heat data can be explained using a theory derived using the lowest-Landau-level approximation(Z. Tes)anović and A. V. Andreev, Phys. Rev. B 49, 4064 (1994) that does not invoke flux lattice melting arguments.

Superfluid Boundary Layer.

PubMed

Stagg, G W; Parker, N G; Barenghi, C F

2017-03-31

We model the superfluid flow of liquid helium over the rough surface of a wire (used to experimentally generate turbulence) profiled by atomic force microscopy. Numerical simulations of the Gross-Pitaevskii equation reveal that the sharpest features in the surface induce vortex nucleation both intrinsically (due to the raised local fluid velocity) and extrinsically (providing pinning sites to vortex lines aligned with the flow). Vortex interactions and reconnections contribute to form a dense turbulent layer of vortices with a nonclassical average velocity profile which continually sheds small vortex rings into the bulk. We characterize this layer for various imposed flows. As boundary layers conventionally arise from viscous forces, this result opens up new insight into the nature of superflows.

Effects of a modulated vortex structure on the diffraction dynamics of ring Airy Gaussian beams.

PubMed

Huang, Xianwei; Shi, Xiaohui; Deng, Zhixiang; Bai, Yanfeng; Fu, Xiquan

2017-09-01

The evolution of the ring Airy Gaussian beams with a modulated vortex in free space is numerically investigated. Compared with the unmodulated vortex, the unique property is that the beam spots first break up, and then gather. The evolution of the beams is influenced by the parameters of the vortex modulation, and the splitting phenomenon gets enhanced with multiple rings becoming light spots if the modulation depth increases. The symmetric branch pattern of the beam spots gets changed when the number of phase folds increases, and the initial modulation phase only impacts the angle of the beam spots. Moreover, a large distribution factor correlates to a hollow Gaussian vortex shape and weakens the splitting and gathering trend. By changing the initial parameters of the vortex modulation and the distribution factor, the peak intensity is greatly affected. In addition, the energy flow and the angular momentum are elucidated with the beam evolution features being confirmed.

Atomic Josephson Vortex

NASA Astrophysics Data System (ADS)

Kaurov, Vitaliy; Kuklov, Anatoly

2006-03-01

We show that atomic Josephson vortices [1] in a quasi-1D atomic junction can be controllably manipulated by imposing a tunneling bias current created by a difference of chemical potentials on the atomic BEC waveguides forming the junction. This effect, which has its origin in the Berry phase structure of a vortex, turns out to be very robust in the whole range of the parameters where such vortices can exist [2]. Acceleration of the vortex up to a certain threshold speed, determined by the strength of the Josephson coupling, results in the phase slip causing switching of the vorticity. This effect is directly related to the interconversion [1], when slow variation of the coupling can cause transformation of the vortex into the dark soliton and vice verse. We also propose that a Josephson vortex can be created by the phase imprinting technique and can be identified by a specific tangential feature in the interference picture produced by expanding clouds released from the waveguides [2]. [1] V. M. Kaurov , A. B. Kuklov, Phys. Rev. A 71, 11601(R) (2005). [2] V. M. Kaurov , A. B. Kuklov cond-mat/0508342

Second harmonic generation of off axial vortex beam in the case of walk-off effect

NASA Astrophysics Data System (ADS)

Chen, Shunyi; Ding, Panfeng; Pu, Jixiong

2016-07-01

Process of off axial vortex beam propagating in negative uniaxial crystal is investigated in this work. Firstly, we get the formulae of the normalized electric field and calculate the location of vortices for second harmonic beam in two type of phase matching. Then, numerical analysis verifies that the intensity distribution and location of vortices of the first order original vortex beam depend on the walk-off angle and off axial magnitude. It is shown that, in type I phase matching, the distribution of vortices is symmetrical about the horizontal axis, the separation distance increases as the off axial magnitude increases or the off axial magnitude deceases. However, in type II phase matching, the vortices are symmetrical along with some vertical axis, and increase of the walk-off angle or off axial magnitude leads to larger separation distance. Finally, the case of high order original off axial vortex beam is also investigated.

Ultra-thin optical vortex phase plate based on the metasurface and the angular momentum transformation

NASA Astrophysics Data System (ADS)

Wang, Wei; Li, Yan; Guo, Zhongyi; Li, Rongzhen; Zhang, Jingran; Zhang, Anjun; Qu, Shiliang

2015-04-01

The ultra-thin optical vortex phase plate (VPP) has been designed and investigated based on the metasurface of the metal rectangular split-ring resonators (MRSRRs) array. The circularly polarized incident light can convert into corresponding cross-polarization transmission light, and the phase and the amplitude of cross-polarization transmission light can be simultaneously governed by modulating two arms of the MRSRR. The MRSRR has been arranged in a special order for forming an ultra-thin optical VPP that can covert a plane wave into a vortex beam with a variety of the topological charges, and the transformation between spin angular momentum (SAM) and orbital angular momentum (OAM) has been discussed in detail. The multi-spectral characteristics of the VPP have also been investigated, and the operating bandwidth of the designed VPP is 190 nm (in the range of 710-900 nm), which enable a potential implication for integrated optics and vortex optics.

Continuous Photo-Oxidation in a Vortex Reactor: Efficient Operations Using Air Drawn from the Laboratory

PubMed Central

2017-01-01

We report the construction and use of a vortex reactor which uses a rapidly rotating cylinder to generate Taylor vortices for continuous flow thermal and photochemical reactions. The reactor is designed to operate under conditions required for vortex generation. The flow pattern of the vortices has been represented using computational fluid dynamics, and the presence of the vortices can be easily visualized by observing streams of bubbles within the reactor. This approach presents certain advantages for reactions with added gases. For reactions with oxygen, the reactor offers an alternative to traditional setups as it efficiently draws in air from the lab without the need specifically to pressurize with oxygen. The rapid mixing generated by the vortices enables rapid mass transfer between the gas and the liquid phases allowing for a high efficiency dissolution of gases. The reactor has been applied to several photochemical reactions involving singlet oxygen (1O2) including the photo-oxidations of α-terpinene and furfuryl alcohol and the photodeborylation of phenyl boronic acid. The rotation speed of the cylinder proved to be key for reaction efficiency, and in the operation we found that the uptake of air was highest at 4000 rpm. The reactor has also been successfully applied to the synthesis of artemisinin, a potent antimalarial compound; and this three-step synthesis involving a Schenk-ene reaction with 1O2, Hock cleavage with H+, and an oxidative cyclization cascade with triplet oxygen (3O2), from dihydroartemisinic acid was carried out as a single process in the vortex reactor. PMID:28781513

Vortices in rotating superfluid 3He.

PubMed

Lounasmaa, O V; Thuneberg, E

1999-07-06

In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe.

Vortices in rotating superfluid 3He

PubMed Central

Lounasmaa, Olli V.; Thuneberg, Erkki

1999-01-01

In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe. PMID:10393895

Laboratory experiments on liquid fragmentation during Earth's core formation

NASA Astrophysics Data System (ADS)

Landeau, M.; Deguen, R.; Olson, P.

2013-12-01

Buoyancy-driven fragmentation of one liquid in another immiscible liquid likely occurred on a massive scale during the formation of the Earth, when dense liquid metal blobs were released within deep molten silicate magma oceans. Another example of this phenomenon is the sudden release of petroleum into the ocean during the Deepwater Horizon disaster (Gulf of Mexico, 2010). We present experiments on the instability and fragmentation of blobs of a heavy liquid released into a lighter immiscible liquid. During the fragmentation process, we observe deformation of the released fluid, formation of filamentary structures, capillary instability, and eventually drop formation. We find that, at low and intermediate Weber numbers (which measures the importance of inertia versus surface tension), the fragmentation regime mainly results from the competition between a Rayleigh-Taylor instability and the roll-up of a vortex ring. At sufficiently high Weber numbers (the relevant regime for core formation), the fragmentation process becomes turbulent. The large-scale flow then behaves as a turbulent vortex ring or a turbulent thermal: it forms a coherent structure whose shape remains self-similar during the fall and which grows by turbulent entrainment of ambient fluid. An integral model based on the entrainment assumption, and adapted to buoyant vortex rings with initial momentum, is consistent with our experimental data. This indicates that the concept of turbulent entrainment is valid for non-dispersed immiscible fluids at large Weber and Reynolds numbers. Series of photographs, turbulent fragmentation regime, time intervals of about 0.2 s. Portions (red boxes) have been magnified (on the right).

Mathematical Modeling of Fluid Flow in a Water Physical Model of an Aluminum Degassing Ladle Equipped with an Impeller-Injector

NASA Astrophysics Data System (ADS)

Gómez, Eudoxio Ramos; Zenit, Roberto; Rivera, Carlos González; Trápaga, Gerardo; Ramírez-Argáez, Marco A.

2013-04-01

In this work, a 3D numerical simulation using a Euler-Euler-based model implemented into a commercial CFD code was used to simulate fluid flow and turbulence structure in a water physical model of an aluminum ladle equipped with an impeller for degassing treatment. The effect of critical process parameters such as rotor speed, gas flow rate, and the point of gas injection (conventional injection through the shaft vs a novel injection through the bottom of the ladle) on the fluid flow and vortex formation was analyzed with this model. The commercial CFD code PHOENICS 3.4 was used to solve all conservation equations governing the process for this two-phase fluid flow system. The mathematical model was reasonably well validated against experimentally measured liquid velocity and vortex sizes in a water physical model built specifically for this investigation. From the results, it was concluded that the angular speed of the impeller is the most important parameter in promoting better stirred baths and creating smaller and better distributed bubbles in the liquid. The pumping effect of the impeller is increased as the impeller rotation speed increases. Gas flow rate is detrimental to bath stirring and diminishes the pumping effect of the impeller. Finally, although the injection point was the least significant variable, it was found that the "novel" injection improves stirring in the ladle.

Numerical investigation of tip clearance cavitation in Kaplan runners

NASA Astrophysics Data System (ADS)

Nikiforova, K.; Semenov, G.; Kuznetsov, I.; Spiridonov, E.

2016-11-01

There is a gap between the Kaplan runner blade and the shroud that makes for a special kind of cavitation: cavitation in the tip leakage flow. Two types of cavitation caused by the presence of clearance gap are known: tip vortex cavitation that appears at the core of the rolled up vortex on the blade suction side and tip clearance cavitation that appears precisely in the gap between the blade tip edge and the shroud. In the context of this work numerical investigation of the model Kaplan runner has been performed taking into account variable tip clearance for several cavitation regimes. The focus is put on investigation of structure and origination of mechanism of cavitation in the tip leakage flow. Calculations have been performed with the help of 3-D unsteady numerical model for two-phase medium. Modeling of turbulent flow in this work has been carried out using full equations of Navier-Stokes averaged by Reynolds with correction for streamline curvature and system rotation. For description of this medium (liquid-vapor) simplification of Euler approach is used; it is based on the model of interpenetrating continuums, within the bounds of this two- phase medium considered as a quasi-homogeneous mixture with the common velocity field and continuous distribution of density for both phases. As a result, engineering techniques for calculation of cavitation conditioned by existence of tip clearance in model turbine runner have been developed. The detailed visualization of the flow was carried out and vortex structure on the suction side of the blade was reproduced. The range of frequency with maximum value of pulsation was assigned and maximum energy frequency was defined; it is based on spectral analysis of the obtained data. Comparison between numerical computation results and experimental data has been also performed. The location of cavitation zone has a good agreement with experiment for all analyzed regimes.

On angled bounce-off impact of a drop impinging on a flowing soap film

NASA Astrophysics Data System (ADS)

Basu, Saikat; Yawar, Ali; Concha, Andres; Bandi, M. M.

2017-12-01

Small drops impinging obliquely on thin flowing soap films frequently demonstrate the rare emergence of bulk elastic effects working in-tandem with the more commonplace hydrodynamic interactions. Three collision regimes are observable: (a) drop piercing through the film, (b) it coalescing with the flow, and (c) it bouncing off the film surface. During impact, the drop deforms along with a bulk elastic deformation of the film. For impacts that are close-to-tangential, the bounce-off regime predominates. We outline a reduced order analytical framework assuming a deformable drop and a deformable three-dimensional film, and the idealization invokes a phase-based parametric study. Angular inclination of the film and the ratio of post and pre-impact drop sizes entail the phase parameters. We also perform experiments with vertically descending droplets (constituted from deionized water) impacting against an inclined soap film, flowing under constant pressure head. Model-predicted phase domain for bounce-off compares well to our experimental findings. Additionally, the experiments exhibit momentum transfer to the film in the form of shed vortex dipoles, along with propagation of free surface waves. On consulting prior published work, we note that for locomotion of water-walking insects using an impulsive action, the momentum distribution to the shed vortices and waves are both significant, taking up respectively 2/3 and 1/3 of the imparted streamwise momentum. Considering the visually similar impulse actions, this theory, despite its assumption of a quiescent liquid bath of infinite depth, is applied to the drop bounce-off experiments, and the resultant shed vortex dipole momenta are compared to the momenta of the coherent vortex structures computed from particle imaging velocimetry data. The magnitudes reveal identical order (10-7 N s), suggesting that notwithstanding the disparities, the bounce-off regime may be tapped as a toy analog for impulse-based interfacial biolocomotion.

Liquid Fuels: Pyrolytic Degradation and Fire Spread Behavior as Influenced by Buoyancy

NASA Technical Reports Server (NTRS)

Yeboah, Yaw D.; Malbrue, Courtney; Savage, Melane; Liao, Bo; Ross, Howard D. (Technical Monitor)

2001-01-01

This work is being conducted by the Combustion and Emission Control Lab in the Engineering Department at Clark Atlanta University under NASA Grant No. NCC3-707. The work aims at providing data to supplement the ongoing NASA research activities on fire spread across liquid pools by providing flow visualization and velocity measurements especially in the gas phase and gas-liquid interface. The fabrication, installation, and testing were completed during this reporting period. The system shakedown and detailed quantitative measurements with High Speed Video and Particle Image Velocimetry (PIV) systems using butanol as fuel were performed. New and interesting results, not previously reported in the literature, were obtained from the experiments using a modified NASA tray and butanol as fuel. Three distinct flame spread regimes, as previously reported, were observed. These were the pseudo-uniform regime below 20 C, the pulsating regime between 22 and 30 C and the uniform regime above about 31 C. In the pulsating regime the jump velocity appeared to be independent of the pool temperature. However, the retreat velocity between jumps appeared to depend on the initial pool temperature. The flame retreated before surging forwards with increasing brightness. Previous literature reported this phenomenon only under microgravity conditions. However, we observed such behavior in our normal gravity experiments. Mini-pulsations behind the flame front were also observed. Two or three of these pulsations were observed within a single flame front pulsating time period. The velocity vector maps of the gas and liquid phases ahead, during, and behind the flame front were characterized. At least one recirculation cell was observed right below the flame front.The size of the liquid phase vortex (recirculation cell) below the flame front appeared to decrease with increasing initial pool temperature. The experiments also showed how multiple vortices developed in the liquid phase. A large recirculation cell, which generally spins counterclockwise as the flame spread from right to left, was observed ahead of and near the flame front in the gas phase. Detailed quantitative measurements will be undertaken with the LDV and PIV systems using the modified NASA tray and propanol.

Vortex depinning as a nonequilibrium phase transition phenomenon: Scaling of current-voltage curves near the low and the high critical-current states in 2 H -Nb S2 single crystals

NASA Astrophysics Data System (ADS)

Bag, Biplab; Sivananda, Dibya J.; Mandal, Pabitra; Banerjee, S. S.; Sood, A. K.; Grover, A. K.

2018-04-01

The vortex depinning phenomenon in single crystals of 2 H -Nb S2 superconductors is used as a prototype for investigating properties of the nonequilibrium (NEQ) depinning phase transition. The 2 H -Nb S2 is a unique system as it exhibits two distinct depinning thresholds, viz., a lower critical current Icl and a higher one Ich. While Icl is related to depinning of a conventional, static (pinned) vortex state, the state with Ich is achieved via a negative differential resistance (NDR) transition where the velocity abruptly drops. Using a generalized finite-temperature scaling ansatz, we study the scaling of current (I)-voltage (V) curves measured across Icl and Ich. Our analysis shows that for I >Icl , the moving vortex state exhibits Arrhenius-like thermally activated flow behavior. This feature persists up to a current value where an inflexion in the IV curves is encountered. While past measurements have often reported similar inflexion, our analysis shows that the inflexion is a signature of a NEQ phase transformation from a thermally activated moving vortex phase to a free flowing phase. Beyond this inflection in IV, a large vortex velocity flow regime is encountered in the 2 H -Nb S2 system, wherein the Bardeen-Stephen flux flow limit is crossed. In this regime the NDR transition is encountered, leading to the high Ich state. The IV curves above Ich we show do not obey the generalized finite-temperature scaling ansatz (as obeyed near Icl). Instead, they scale according to the Fisher's scaling form [Fisher, Phys. Rev. B 31, 1396 (1985), 10.1103/PhysRevB.31.1396] where we show thermal fluctuations do not affect the vortex flow, unlike that found for depinning near Icl.

A Computational Fluid Dynamics Study of Swirling Flow Reduction by using Anti-vortex Baffle

NASA Technical Reports Server (NTRS)

Yang, H. Q.; Peugeot, John W.; West, Jeff S..

2013-01-01

An anti-vortex baffle is a liquid propellant management device placed adjacent to an outlet of the propellant tank. Its purpose is to substantially reduce or eliminate the formation of free surface dip and vortex, as well as prevent vapor ingestion into the outlet, as the liquid drains out through the flight. To design an effective anti-vortex baffle, Computational Fluid Dynamic (CFD) simulations were undertaken for the NASA Ares I vehicle LOX tank subjected to the simulated flight loads with and without the anti-vortex baffle. The Six Degree-Of-Freedom (6- DOF) dynamics experienced by the Crew Launch Vehicle (CLV) during ascent were modeled by modifying the momentum equations in a CFD code to accommodate the extra body forces from the maneuvering in a non-inertial frame. The present analysis found that due to large moments, the CLV maneuvering has significant impact on the vortical flow generation inside the tank. Roll maneuvering and side loading due to pitch and yaw are shown to induce swirling flow. The vortical flow due to roll is symmetrical with respect to the tank centerline, while those induced by pitch and yaw maneuverings showed two vortices side by side. The study found that without the anti-vortex baffle, the swirling flow caused surface dip during the late stage of drainage and hence early vapor ingestion. The flow can also be non-uniform in the drainage pipe as the secondary swirling flow velocity component can be as high as 10% of the draining velocity. An analysis of the vortex dynamics shows that the swirling flow in the drainage pipe during the Upper Stage burn is mainly the result of residual vortices inside the tank due to conservation of angular momentum. The study demonstrated that the swirling flow in the drainage pipe can be effectively suppressed by employing the anti-vortex baffle.

A Computational Fluid Dynamics Study of Swirling Flow Reduction by Using Anti-Vortex Baffle

NASA Technical Reports Server (NTRS)

Yang, H. Q.; Peugeot, John W.; West, Jeff S.

2017-01-01

An anti-vortex baffle is a liquid propellant management device placed adjacent to an outlet of the propellant tank. Its purpose is to substantially reduce or eliminate the formation of free surface dip and vortex, as well as prevent vapor ingestion into the outlet, as the liquid drains out through the flight. To design an effective anti-vortex baffle, Computational Fluid Dynamic (CFD) simulations were undertaken for the NASA Ares I vehicle LOX tank subjected to the simulated flight loads with and without the anti-vortex baffle. The Six Degree-Of-Freedom (6-DOF) dynamics experienced by the Crew Launch Vehicle (CLV) during ascent were modeled by modifying the momentum equations in a CFD code to accommodate the extra body forces from the maneuvering in a non-inertial frame. The present analysis found that due to large moments, the CLV maneuvering has a significant impact on the vortical flow generation inside the tank. Roll maneuvering and side loading due to pitch and yaw are shown to induce swirling flow. The vortical flow due to roll is symmetrical with respect to the tank centerline, while those induced by pitch and yaw maneuverings showed two vortices side by side. The study found that without the anti-vortex baffle, the swirling flow caused surface dip during the late stage of drainage and hence early vapor ingestion. The flow can also be non-uniform in the drainage pipe as the secondary swirling flow velocity component can be as high as 10% of the draining velocity. An analysis of the vortex dynamics shows that the swirling flow in the drainage pipe during the Upper Stage burn is mainly the result of residual vortices inside the tank due to the conservation of angular momentum. The study demonstrated that the swirling flow in the drainage pipe can be effectively suppressed by employing the anti-vortex baffle.

Magneto-optical observation of twisted vortices in type-II superconductors

NASA Astrophysics Data System (ADS)

Indenbom, M. V.; van der Beek, C. J.; Berseth, V.; Benoit, W.; D'Anna, G.; Erb, A.; Walker, E.; Flükiger, R.

1997-02-01

When magnetic flux penetrates a type-II superconductor, it does so as quantized flux lines or vortex lines, so called because each is surrounded by a supercurrent vortex. Interactions between such vortices lead to a very rich and well characterized phenomenology for this 'mixed state'. But an outstanding question remains: are individual vortex lines 'strong', or can they easily be cut and made to pass through one another? The concept of vortex cutting was originally proposed to account for dissipation observed in superconducting wires oriented parallel to an applied magnetic field, where the vortex lines and transport current should be in a force-free configuration1-6. Previous experiments, however, have been unable to establish the vortex topology in the force-free configuration or the size of the energy barrier for vortex cutting. Here we report magneto-optical images of YBa2Cu3O7-δ samples in the force-free configuration which show that thousands of vortex lines can twist together to form highly stable structures. In some cases, these 'vortex twisters' interact with one another to produce wave-like dynamics. Our measurements also determine directly the current required to initiate vortex cutting, and show that it is much higher than that needed to overcome the pinning of vortices by material defects. This implies that thermodynamic phases of entangled vortices7-10 are intrinsically stable and may occupy a significant portion of the mixed-state phase diagram for type-II superconductors.

Modeling the quasi-biennial oscillation's effect on the winter stratospheric circulation

NASA Technical Reports Server (NTRS)

O'Sullivan, Donal; Young, Richard E.

1992-01-01

The influence of the equatorial quasi-biennial oscillation (QBO) on the winter middle atmosphere is modeled with a mechanistic global primitive equation model. The model's polar vortex evolution is sensitive to the lower stratosphere's tropical winds, with the polar vortex becoming more (less) disturbed as the lower stratospheric winds are more easterly (westerly). This agrees with the observed relationship between wintertime polar circulation strength and the phase of the QBO in the lower stratosphere. In these experiments it is the extratropical planetary Rossby waves that provide the tropical-extratropical coupling mechanism. More easterly tropical winds in the lower stratosphere act to confine the extratropical Rossby waves farther north and closer to the vortex at the QBO altitudes, weakening the vortex relative to the case of westerly QBO phase. While the QBO winds occur in the lower stratosphere, the anomaly in the polar vortex strength is strongest at higher levels.

Intra-seasonal variability of extreme boreal stratospheric polar vortex events and their precursors

NASA Astrophysics Data System (ADS)

Díaz-Durán, Adelaida; Serrano, Encarna; Ayarzagüena, Blanca; Abalos, Marta; de la Cámara, Alvaro

2017-11-01

The dynamical variability of the boreal stratospheric polar vortex has been usually analysed considering the extended winter as a whole or only focusing on December, January and February. Yet recent studies have found intra-seasonal differences in the boreal stratospheric dynamics. In this study, the intra-seasonal variability of anomalous wave activity preceding polar vortex extremes in the Northern Hemisphere is examined using ERA-Interim reanalysis data. Weak (WPV) and strong (SPV) polar vortex events are grouped into early, mid- or late winter sub-periods depending on the onset date. Overall, the strongest (weakest) wave-activity anomalies preceding polar vortex extremes are found in mid- (early) winter. Most of WPV (SPV) events in early winter occur under the influence of east (west) phase of the Quasi-Biennial Oscillation (QBO) and an enhancement (inhibition) of wavenumber-1 wave activity (WN1). Mid- and late winter WPV events are preceded by a strong vortex and an enhancement of WN1 and WN2, but the spatial structure of the anomalous wave activity and the phase of the QBO are different. Prior to mid-winter WPVs the enhancement of WN2 is related to the predominance of La Niña and linked to blockings over Siberia. Mid-winter SPV events show a negative phase of the Pacific-North America pattern that inhibits WN1 injected into the stratosphere. This study suggests that dynamical features preceding extreme polar vortex events in mid-winter should not be generalized to other winter sub-periods.

Ultra-broadband tunable (0.67-2.57 µm) optical vortex parametric oscillator

NASA Astrophysics Data System (ADS)

Araki, Shungo; Suzuki, Kensuke; Nishida, Shigeki; Mamuti, Roukuya; Miyamoto, Katsuhiko; Omatsu, Takashige

2017-10-01

We demonstrate an ultra-broadband (>2-octave band) tunable optical vortex laser comprising an optical-vortex-pumped optical parametric oscillator by employing a nanosecond pulse (˜10 ns) green laser and cascaded non-critical phase-matching LiB3O5 crystals (45 mm long each). With this system, an optical vortex output was produced over an extremely wide wavelength range of 0.67-2.57 µm.

Mixing device for materials with large density differences

DOEpatents

Gregg, David W.

1994-01-01

An auger-tube pump mixing device for mixing materials with large density differences while maintaining low stirring RPM and low power consumption. The mixing device minimizes the formation of vortexes and minimizes the incorporation of small bubbles in the liquid during mixing. By avoiding the creation of a vortex the device provides efficient stirring of full containers without spillage over the edge. Also, the device solves the problem of effective mixing in vessels where the liquid height is large compared to the diameter. Because of the gentle stirring or mixing by the device, it has application for biomedical uses where cell damage is to be avoided.

Mixing device for materials with large density differences

DOEpatents

Gregg, D.W.

1994-08-16

An auger-tube pump mixing device is disclosed for mixing materials with large density differences while maintaining low stirring RPM and low power consumption. The mixing device minimizes the formation of vortexes and minimizes the incorporation of small bubbles in the liquid during mixing. By avoiding the creation of a vortex the device provides efficient stirring of full containers without spillage over the edge. Also, the device solves the problem of effective mixing in vessels where the liquid height is large compared to the diameter. Because of the gentle stirring or mixing by the device, it has application for biomedical uses where cell damage is to be avoided. 2 figs.

Broadband and high efficiency all-dielectric metasurfaces for wavefront steering with easily obtained phase shift

NASA Astrophysics Data System (ADS)

Yang, Hui; Deng, Yan

2017-12-01

All-dielectric metasurfaces for wavefront deflecting and optical vortex generating with broadband and high efficiency are demonstrated. The unit cell of the metasurfaces is optimized to function as a half wave-plate with high polarization conversion efficiency (94%) and transmittance (94.5%) at the telecommunication wavelength. Under such a condition, we can get rid of the complicated parameter sweep process for phase shift selecting. Hence, a phase coverage ranges from 0 to 2 π can be easily obtained by introducing the Pancharatnam-Berry phase. Metasurfaces composed of the two pre-designed super cells are demonstrated for optical beam deflecting and vortex beam generating. It is found that the metasurfaces with more phase shift sampling points (small phase shift increment) exhibit better performance. Moreover, optical vortex beams can be generated by the designed metasurfaces within a wavelength range of 200 nm. These results will provide a viable route for designing broadband and high efficiency devices related to phase modulation.

Uranium droplet core nuclear rocket

NASA Technical Reports Server (NTRS)

Anghaie, Samim

1991-01-01

Uranium droplet nuclear rocket is conceptually designed to utilize the broad temperature range ofthe liquid phase of metallic uranium in droplet configuration which maximizes the energy transfer area per unit fuel volume. In a baseline system dissociated hydrogen at 100 bar is heated to 6000 K, providing 2000 second of Isp. Fission fragments and intense radian field enhance the dissociation of molecular hydrogen beyond the equilibrium thermodynamic level. Uranium droplets in the core are confined and separated by an axisymmetric vortex flow generated by high velocity tangential injection of hydrogen in the mid-core regions. Droplet uranium flow to the core is controlled and adjusted by a twin flow nozzle injection system.

Propagation of optical vortices with fractional topological charge in free space

NASA Astrophysics Data System (ADS)

Ali, Tamelia; Kreminska, Liubov; Golovin, Andrii B.; Crouse, David T.

2014-10-01

The behavior of the optical vortices with fractional topological charges in the far-field is assessed through numerical modeling and confirmed by experimental results. The generation of fractional topological charge variations of the phase within a Gaussian beam was achieved by using a liquid crystal spatial light modulator (LCoS SLM). It is shown that a laser beam carrying an optical vortex with a fractional topological charge evolves into a beam with a topological charge of integer value, specifically an integer value closer to the fractional number in the far field. A potential application of this work is for data transmission within optical telecommunication systems.

Generating broadband vortex modes in ring-core fiber by using a plasmonic q-plate.

PubMed

Ye, Jingfu; Li, Yan; Han, Yanhua; Deng, Duo; Su, Xiaoya; Song, He; Gao, Jianmin; Qu, Shiliang

2017-08-15

A mode convertor was proposed and investigated for generating vortex modes in a ring-core fiber based on a plasmonic q-plate (PQP), which is composed of specially organized L-shaped resonator (LSR) arrays. A multicore fiber was used to transmit fundamental modes, and the LSR arrays were used to modulate phases of these fundamental modes. Behind the PQP, the transmitted fundamental modes with gradient phase distribution can be considered as the incident lights for generating broadband vortex modes in the ring-core fiber filter. The topological charges of generated vortex modes can be various by using an optical PQP with different q, and the chirality of the generated vortex mode can be controlled by the sign of q and handedness of the incident circularly polarized light. The operation bandwidth is 800 nm in the range of 1200-2000 nm, which covers six communication bands from the O band to the U band. The separation of vortex modes also was addressed by using a dual ring-core fiber. The mode convertor is of potential interest for connecting a traditional network and vortex communication network.

Spatially resolved resistivity near the vortex lattice phase transition in Bi 2Sr 2CaCu 2O 8+δ single crystals

NASA Astrophysics Data System (ADS)

Berseth, V.; Indenbom, M. V.; van der Beek, C. J.; D'Anna, G.; Benoit, W.

1997-08-01

Using a multiterminal contact configuration, we investigate the local variations of the resistivity drop near the vortex lattice first order phase transition in a very homogeneous Bi2Sr2CaCu2O8+δ (BSCCO) single crystal.

Laboratory demonstration of an optical vortex mask coronagraph using photonic crystal

NASA Astrophysics Data System (ADS)

Murakami, N.; Baba, N.; Ise, A.; Sakamoto, M.; Oka, K.

2010-10-01

Photonic crystal, artificial periodic nanostructure, is an attractive device for constructing focal-plane phase-mask coronagraphs such as segmented phase masks (four-quadrant, eight-octant, and 4N-segmented ones) and an optical vortex mask (OVM), because of its extremely small manufacturing defect. Recently, speckle-noise limited contrast has been demonstrated for two monochromatic lasers by using the eight-octant phase-mask made of the photonic crystal (Murakami et al. 2010, ApJ, 714, 772). We applied the photonic-crystal device to the OVM coronagraph. The OVM is more advantageous over the segmented phase masks because it does not have discontinuities other than a central singular point and provides a full on-sky field of view. For generating an achromatic optical vortex, we manufactured an axially-symmetric half-wave plate (ASHWP). It is expected that a size of the manufacturing defect due to the central singularity is an order of several hundreds nanometers. The ASHWP is placed between two circular polarizers for modulating a Pancharatnam phase. A continuous spiral phase modulation is then implemented achromatically. We carried out preliminary laboratory demonstration of the OVM coronagraph using two monochromatic lasers as a model star (wavelengths of 532 nm and 633 nm). We report a principle of the achromatic optical-vortex generation, and results of the laboratory demonstration of the OVM coronagraph.

Development of the Technology of Vortex Diagnostics to Improve the Safety of Operation of Nuclear Reactors

NASA Astrophysics Data System (ADS)

Mitrofanova, O. V.; Ivlev, O. A.; Pozdeeva, I. G.; Urtenov, D. S.

2017-11-01

The results of studies are aimed at developing theoretical foundations and instrumentation system to ensure a technology of vortex diagnostics of the state of flows of fluids for nuclear power installations with power water reactors and fast neutrons reactors with liquid-metal coolants. The technology of vortex diagnostics is based on the study of acoustic, magneto-hydrodynamic and resonant effects related to the formation of stable vortex structures. For creation a system of monitoring and diagnostics of the crisis phenomena due to hydrodynamics of the flow, it is proposed to use acoustic method to record the radiation of elastic waves in the fluids caused by the dynamic local rearrangement of its structure.

Optical vortex beams: Generation, propagation and applications

NASA Astrophysics Data System (ADS)

Cheng, Wen

An optical vortex (also known as a screw dislocation or phase singularity) is one type of optical singularity that has a spiral phase wave front around a singularity point where the phase is undefined. Optical vortex beams have a lot of applications in areas such as optical communications, LADAR (laser detection and ranging) system, optical tweezers, optical trapping and laser beam shaping. The concepts of optical vortex beams and methods of generation are briefly discussed. The properties of optical vortex beams propagating through atmospheric turbulence have been studied. A numerical modeling is developed and validated which has been applied to study the high order properties of optical vortex beams propagating though a turbulent atmosphere. The simulation results demonstrate the advantage that vectorial vortex beams may be more stable and maintain beam integrity better when they propagate through turbulent atmosphere. As one important application of optical vortex beams, the laser beam shaping is introduced and studied. We propose and demonstrate a method to generate a 2D flat-top beam profile using the second order full Poincare beams. Its applications in two-dimensional flat-top beam shaping with spatially variant polarization under low numerical aperture focusing have been studied both theoretically and experimentally. A novel compact flat-top beam shaper based on the proposed method has been designed, fabricated and tested. Experimental results show that high quality flat-top profile can be obtained with steep edge roll-off. The tolerance to different input beam sizes of the beam shaper is also verified in the experimental demonstration. The proposed and experimentally verified LC beam shaper has the potential to become a promising candidate for compact and low-cost flat-top beam shaping in areas such as laser processing/machining, lithography and medical treatment.

Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

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

Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.

2015-06-27

Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

Direct observation of the flux-line vortex glass phase in a type II superconductor.

PubMed

Divakar, U; Drew, A J; Lee, S L; Gilardi, R; Mesot, J; Ogrin, F Y; Charalambous, D; Forgan, E M; Menon, G I; Momono, N; Oda, M; Dewhurst, C D; Baines, C

2004-06-11

The order of the vortex state in La1.9Sr0.1CuO4 is probed using muon-spin rotation and small-angle neutron scattering. A transition from a Bragg glass to a vortex glass is observed, where the latter is composed of disordered vortex lines. In the vicinity of the transition the microscopic behavior reflects a delicate interplay of thermally induced and pinning-induced disorder.

Large-Scale Coherent Vortex Formation in Two-Dimensional Turbulence

NASA Astrophysics Data System (ADS)

Orlov, A. V.; Brazhnikov, M. Yu.; Levchenko, A. A.

2018-04-01

The evolution of a vortex flow excited by an electromagnetic technique in a thin layer of a conducting liquid was studied experimentally. Small-scale vortices, excited at the pumping scale, merge with time due to the nonlinear interaction and produce large-scale structures—the inverse energy cascade is formed. The dependence of the energy spectrum in the developed inverse cascade is well described by the Kraichnan law k -5/3. At large scales, the inverse cascade is limited by cell sizes, and a large-scale coherent vortex flow is formed, which occupies almost the entire area of the experimental cell. The radial profile of the azimuthal velocity of the coherent vortex immediately after the pumping was switched off has been established for the first time. Inside the vortex core, the azimuthal velocity grows linearly along a radius and reaches a constant value outside the core, which agrees well with the theoretical prediction.

Film-Cooling Heat-Transfer Measurements Using Liquid Crystals

NASA Technical Reports Server (NTRS)

Hippensteele, Steven A.

1997-01-01

The following topics are discussed: (1) The Transient Liquid-Crystal Heat-Transfer Technique; (2) 2-D Film-Cooling Heat-Transfer on an AlliedSignal Vane; and (3) Effects of Tab Vortex Generators on Surface Heat Transfer. Downstream of a Jet in Crossflow.

Poincare oscillations and geostrophic adjustment in a rotating paraboloid

NASA Astrophysics Data System (ADS)

Kalashnik, M.; Kakhiani, V.; Patarashvili, K.; Tsakadze, S.

2009-10-01

Free liquid oscillations (Poincare oscillations) in a rotating paraboloid are investigated theoretically and experimentally. Within the framework of shallow-water theory, with account for the centrifugal force, expressions for the free oscillation frequencies are obtained and corrections to the frequencies related with the finiteness of the liquid depth are found. It is shown that in the rotating liquid, apart from the wave modes of free oscillations, a stationary vortex mode is also generated, that is, a process of geostrophic adjustment takes place. Solutions of the shallow-water equations which describe the wave dynamics of the adjustment process are presented. In the experiments performed the wave and vortex modes were excited by removing a previously immersed hemisphere from the central part of the paraboloid. Good agreement between theory and experiment was obtained. Address: alex_gaina@yahoo.com Database: phy

Birth and evolution of an optical vortex.

PubMed

Vallone, Giuseppe; Sponselli, Anna; D'Ambrosio, Vincenzo; Marrucci, Lorenzo; Sciarrino, Fabio; Villoresi, Paolo

2016-07-25

When a phase singularity is suddenly imprinted on the axis of an ordinary Gaussian beam, an optical vortex appears and starts to grow radially, by effect of diffraction. This radial growth and the subsequent evolution of the optical vortex under focusing or imaging can be well described in general within the recently introduced theory of circular beams, which generalize the hypergeometric-Gaussian beams and which obey novel kinds of ABCD rules. Here, we investigate experimentally these vortex propagation phenomena and test the validity of circular-beam theory. Moreover, we analyze the difference in radial structure between the newly generated optical vortex and the vortex obtained in the image plane, where perfect imaging would lead to complete closure of the vortex core.

Mathematical investigation of tsunami-like long waves interaction with submerge dike of different thickness

NASA Astrophysics Data System (ADS)

Zhiltsov, Konstantin; Kostyushin, Kirill; Kagenov, Anuar; Tyryshkin, Ilya

2017-11-01

This paper presents a mathematical investigation of the interaction of a long tsunami-type wave with a submerge dike. The calculations were performed by using the freeware package OpenFOAM. Unsteady two-dimensional Navier-Stokes equations were used for mathematical modeling of incompressible two-phase medium. The Volume of Fluid (VOF) method is used to capture the free surface of a liquid. The effects caused by long wave of defined amplitude motion through a submerged dike of varying thickness were discussed in detail. Numerical results show that after wave passing through the barrier, multiple vortex structures were formed behind. Intensity of vortex depended on the size of the barrier. The effectiveness of the submerge barrier was estimated by evaluating the wave reflection and transmission coefficients using the energy integral method. Then, the curves of the dependences of the reflection and transmission coefficients were obtained for the interaction of waves with the dike. Finally, it was confirmed that the energy of the wave could be reduced by more than 50% when it passed through the barrier.

Simultaneous determination of organophosphorus pesticides and phthalates in baby food samples by ultrasound-vortex-assisted liquid-liquid microextraction and GC-IT/MS.

PubMed

Notardonato, Ivan; Salimei, Elisabetta; Russo, Mario Vincenzo; Avino, Pasquale

2018-05-01

Baby foods are either a soft, liquid paste or an easily chewed food since babies lack developed muscles and teeth to chew effectively. Babies typically move to consuming baby food once nursing or formula is not sufficient for the child's appetite. Some commercial baby foods have been criticized for their contents. This article focuses on the simultaneous determination of organophosphorus pesticides and phthalates by means of a method based on ultrasound-vortex-assisted liquid-liquid microextraction coupled with gas chromatography-ion trap mass spectrometry (GC-IT/MS). The protocol developed allowed the determination of six phthalates [dimethyl phthalate, diethyl phthalate, dibutyl phthalate, isobutyl cyclohexyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate] and 19 organophosphorus pesticides. Freeze-dried product samples (0.1-0.2 g) were dissolved in 10 mL of warm distilled water along with 5 μL of an internal standard (anthracene at 10 mg mL -1 in acetone): the choice of extraction solvent was studied, with the most suitable being n-heptane, which is used for phthalate determination in similar matrices. The solution, held for 5 min in a vortex mixer and for 6 min in a 100-W ultrasonic bath to favor solvent dispersion and consequently analyte extraction, was centrifuged at 4000 rpm for 30 min. Then 1 μL was injected into the GC-IT/MS system (SE-54 capillary column; length 30 m, inner diameter 250 μm, film thickness 0.25 μm). All analytical parameters investigated are discussed in depth. The method was applied to real commercial freeze-dried samples: significant contaminant concentrations were not found. Graphical abstract Simultaneous and sensitive determination of organophosphorus pesticides and phthalates in baby foods by the ultrasound-vortex-assisted liquid-liquid microextraction ֪gas chromatography-ion trap mass spectrometry procedure. 1 methacrifos, 2 pirofos, 3 phorate, 4 seraphos, 5 diazinon, 6 etrimphos, 7 dichlofenthion, 8 chlorpyrifos-methyl, 9 pirimiphos-methyl, 10 malathion, 11 chlorpyrifos, 12 parathion-ethyl, 13 pirimiphos-ethyl, 14 bromophos, 15 chlorfenvinphos, 16 bromophos-ethyl, 17 stirophos, 18 diethion, 19 coumaphos, A dimethyl phthalate, B diethyl phthalate, C dibutyl phthalate, D butyl cyclohexyl phthalate, E benzyl butyl phthalate, F bis(2-ethylhexyl) phthalate, IS internal standard.

Scattering of a vortex pair by a single quantum vortex in a Bose–Einstein condensate

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

Smirnov, L. A., E-mail: smirnov-lev@allp.sci-nnov.ru; Smirnov, A. I., E-mail: smirnov@appl.sci-nnov.ru; Mironov, V. A.

We analyze the scattering of vortex pairs (the particular case of 2D dark solitons) by a single quantum vortex in a Bose–Einstein condensate with repulsive interaction between atoms. For this purpose, an asymptotic theory describing the dynamics of such 2D soliton-like formations in an arbitrary smoothly nonuniform flow of a ultracold Bose gas is developed. Disregarding the radiation loss associated with acoustic wave emission, we demonstrate that vortex–antivortex pairs can be put in correspondence with quasiparticles, and their behavior can be described by canonical Hamilton equations. For these equations, we determine the integrals of motion that can be used tomore » classify various regimes of scattering of vortex pairs by a single quantum vortex. Theoretical constructions are confirmed by numerical calculations performed directly in terms of the Gross–Pitaevskii equation. We propose a method for estimating the radiation loss in a collision of a soliton-like formation with a phase singularity. It is shown by direct numerical simulation that under certain conditions, the interaction of vortex pairs with a core of a single quantum vortex is accompanied by quite intense acoustic wave emission; as a result, the conditions for applicability of the asymptotic theory developed here are violated. In particular, it is visually demonstrated by a specific example how radiation losses lead to a transformation of a vortex–antivortex pair into a vortex-free 2D dark soliton (i.e., to the annihilation of phase singularities).« less

Determination of ochratoxin A in fruit juice by high-performance liquid chromatography after vortex-assisted emulsification microextraction based on solidification of floating organic drop.

PubMed

Asadi, Mohammad

2018-03-01

A rapid, simple, and green vortex-assisted emulsification microextraction method based on solidification of floating organic drop was developed for the extraction and determination of ochratoxin A (OTA) with high-performance liquid chromatography. Some factors influencing the extraction efficiency of OTA such as the type and volume of extraction solvent, sample pH, salt concentration, vortex time, and sample volume were optimized. Under optimized conditions, the calibration curve exhibited linearity in the range of 50.0-500 ng L -1 with a coefficient of determination higher than 0.999. The limit of detection was 15.0 ng L -1 . The inter- and intra-assays relative standard deviations were in a range of 4.7-8.7%. The accuracy of the developed method was investigated through recovery experiments, and it was successfully used for the quantification of OTA in 40 samples of fruit juice.

Flame Stability in a Trapped-Vortex Spray-Combustor

NASA Astrophysics Data System (ADS)

Chakka, P.; Mancilla, P. C.; Acharya, S.

1999-11-01

Flame stabilization mechanisms in a Trapped-Vortex (TV) cavity is investigated experimentally and computationally in the current research. The TV-cavity is placed coaxially in the combustor and the flame is maintained through injection of liquid fuel spray and air from the inside face of the afterbody. This concept was introduced by Roquemore and company of Wright-Patterson AFB for gaseous fuel injection into the cavity and is extended for liquid fuel sprays in the current research. The flame holding capability of the TV-cavity is studied for different equivalence ratios of the secondary injection and overall Lean Blow-Out (LBO) limits are presented for different primary and secondary flow rates. The interaction and mixing of the main flow with the secondary vortex flow is investigated through the Laser Doppler Velocimetry measurements taken through a quartz window near the cavity. Also, temperature distribution through IR measurements and pressure fluctuations inside the chamber are presented for complete performance analysis of the TV cavity combustor.

Ionic liquid based vortex assisted liquid-liquid microextraction combined with liquid chromatography mass spectrometry for the determination of bisphenols in thermal papers with the aid of response surface methodology.

PubMed

Asati, Ankita; Satyanarayana, G N V; Panchal, Smita; Thakur, Ravindra Singh; Ansari, Nasreen G; Patel, Devendra K

2017-08-04

A sensitive, rapid and efficient ionic liquid-based vortex assisted liquid-liquid microextraction (IL-VALLME) with Liquid Chromatography Mass spectrometry (LC-MS/MS) method is proposed for the determination of bisphenols in thermal paper. Extraction factors were systematically optimized by response surface methodology. Experimental factors showing significant effects on the analytical responses were evaluated using design of experiment. The limit of detection for Bisphenol-A (BPA) and Bisphenol-S (BPS) in thermal paper were 1.25 and 0.93μgkg -1 respectively. The dynamic linearity range for BPA was between 4 and 100μgkg -1 and the determination of coefficient (R 2 ) was 0.996. The values of the same parameters were 3-100μgkg -1 and 0.998 for BPS. The extraction recoveries of BPA and BPS in thermal paper were 101% and 99%. Percent relative standard deviation (% RSD) for matrix effect and matrix match effects were not more than 10%, for both bisphenols. The proposed method uses a statistical approach for the analysis of bisphenols in environmental samples, and is easy, rapid, requires minimum organic solvents and efficient. Copyright © 2017 Elsevier B.V. All rights reserved.

A Facile Vortex-Assisted Dispersive Liquid-Liquid Microextraction Method for the Determination of Uranyl Ion at Low Levels by Spectrophotometry.

PubMed

Corazza, Marcela Zanetti; Pires, Igor Matheus Ruiz; Diniz, Kristiany Moreira; Segatelli, Mariana Gava; Tarley, César Ricardo Teixeira

2015-08-01

A facile and reliable UV-Vis spectrophotometric method associated with vortex-assisted dispersive liquid-liquid microextraction has been developed and applied to the determination of U(VI) at low levels in water samples. It was based on preconcentration of 24.0 mL sample at pH 8.0 in the presence of 7.4 µmol L(-1) 1-(2-pyridylazo)-2-naphthol, 1.0 mL of methanol as disperser solvent and 1.0 mL of chloroform as extraction solvent. A high preconcentration factor was achieved (396 times), thus providing a wide analytical curve from 6.9 up to 75.9 µg L(-1) (r=0.9982) and limits of detection and quantification of 0.40 and 1.30 µg L(-1), respectively. When necessary, EDTA or KCN can be used to remove interferences of foreign ions. The method was applied to the analysis of real water samples, such as tap, mineral and lake waters with good recovery values.

Jet Simulation in a Diesel Engine

NASA Astrophysics Data System (ADS)

Xu, Zhiliang

2005-03-01

We present a numerical study of the jet breakup and spray formation in a diesel engine by the Front Tracking method. The mechanisms of jet breakup and spray formation of a high speed diesel jet injected through a circular nozzle are the key to design a fuel efficient, nonpolluting diesel engine. We conduct the simulations for the jet breakup within a 2D axis-symmetric geometry. Our goal is to model the spray at a micro-physical level, with the creation of individual droplets. The problem is multiscale. The droplets are a few microns in size. The nozzle is about 0.2 mm in diameter and 1 mm in length. To resolve various physical patterns such as vortex, shock waves, vacuum and track droplets and spray, the Burger-Colella adaptive mesh refinement technique is used. To simulate the spray formation, we model mixed vapor-liquid region through a heterogeneous model with dynamic vapor bubble insertion. The formation of the cavitation is represented by the dynamic creation of vapor bubbles. On the liquid/vapor interface, a phase transition problem is solved numerically. The phase transition is governed by the compressible Euler equations with heat diffusion. Our solution is a new description for the Riemann problem associated with a phase transition in a fully compressible fluid.

Oscillation of an isolated liquid plug inside a dry capillary

NASA Astrophysics Data System (ADS)

Srinivasan, Vyas; Kumar, Siddhartha; Asfer, Mohammed; Khandekar, Sameer

2017-11-01

The present work reports an experimental study on the dynamics of partially wetting isolated liquid plug (DI water), which is made to oscillate inside a square, glass capillary tube (1 mm × 1 mm; 60 mm length). The liquid plug is made to oscillate pneumatically at two different frequencies (0.25 and 0.35 Hz), using a cam-follower mechanism. Bright field imaging is used to visualize the three-phase contact line behavior, while, micro-Particle Imaging Velocimetry (PIV) apparatus is used to discern the nature of flow inside the oscillating liquid plug. During a cycle, due to the partial wetting nature of DI water, the three-phase contact line at the menisci gets pinned at the extreme end of each stroke, where the dynamic apparent contact angle gets drastically altered before the initiation of the next stroke. The difference between the apparent contact angle of the front and rear meniscus are seen to be a function of the oscillating frequency; the difference increasing with increasing frequency. The flow inside the liquid plug reveals unique non-Poiseuille flow features near the meniscus, due to free-slip boundary condition, which leads to formation of distinct vortex pairs behind it. The vortices too change their direction during each stroke of the oscillation, eventually leading to an alternating recirculation pattern inside the plug. The results clearly indicate that improved mathematical models are required for predicting transport parameters in such flows, which are important in engineering systems such as pulsating heat pipes, lab-on-chip devices and PEM fuel cells.

New techniques for experimental generation of two-dimensional blade-vortex interaction at low Reynolds numbers

NASA Technical Reports Server (NTRS)

Booth, E., Jr.; Yu, J. C.

1986-01-01

An experimental investigation of two dimensional blade vortex interaction was held at NASA Langley Research Center. The first phase was a flow visualization study to document the approach process of a two dimensional vortex as it encountered a loaded blade model. To accomplish the flow visualization study, a method for generating two dimensional vortex filaments was required. The numerical study used to define a new vortex generation process and the use of this process in the flow visualization study were documented. Additionally, photographic techniques and data analysis methods used in the flow visualization study are examined.

Three-wave electron vortex lattices for measuring nanofields.

PubMed

Dwyer, C; Boothroyd, C B; Chang, S L Y; Dunin-Borkowski, R E

2015-01-01

It is demonstrated how an electron-optical arrangement consisting of two electron biprisms can be used to generate three-wave vortex lattices with effective lattice spacings between 0.1 and 1 nm. The presence of vortices in these lattices was verified by using a third biprism to perform direct phase measurements via off-axis electron holography. The use of three-wave lattices for nanoscale electromagnetic field measurements via vortex interferometry is discussed, including the accuracy of vortex position measurements and the interpretation of three-wave vortex lattices in the presence of partial spatial coherence. Copyright © 2014 Elsevier B.V. All rights reserved.

Topological dynamics of vortex-line networks in hexagonal manganites

NASA Astrophysics Data System (ADS)

Xue, Fei; Wang, Nan; Wang, Xueyun; Ji, Yanzhou; Cheong, Sang-Wook; Chen, Long-Qing

2018-01-01

The two-dimensional X Y model is the first well-studied system with topological point defects. On the other hand, although topological line defects are common in three-dimensional systems, the evolution mechanism of line defects is not fully understood. The six domains in hexagonal manganites converge to vortex lines in three dimensions. Using phase-field simulations, we predicted that during the domain coarsening process, the vortex-line network undergoes three types of basic topological changes, i.e., vortex-line loop shrinking, coalescence, and splitting. It is shown that the vortex-antivortex annihilation controls the scaling dynamics.

Phase coexistence and electric-field control of toroidal order in oxide superlattices

DOE PAGES

Damodaran, A. R.; Clarkson, J. D.; Hong, Z.; ...

2017-08-07

Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO 3/SrTiO 3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a 1/a 2 phase. At room temperature, the coexisting vortexmore » and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Here, our findings suggest new cross-coupled functionalities.« less

Effect of a crystal-melt interface on Taylor-vortex flow

NASA Technical Reports Server (NTRS)

Mcfadden, G. B.; Coriell, S. R.; Murray, B. T.; Glicksman, M. E.; Selleck, M. E.

1990-01-01

The linear stability of circular Couette flow between concentric infinite cylinders is considered for the case that the stationary outer cylinder is a crystal-melt interface rather than a rigid surface. A radial temperature difference is maintained across the liquid gap, and equations for heat transport in the crystal and melt phases are included to extend the ordinary formulation of this problem. The stability of this two-phase system depends on the Prandtl number. For small Prandtl number the linear stability of the two-phase system is given by the classical results for a rigid-walled system. For increasing values of the Prandtl number, convective heat transport becomes significant and the system becomes increasingly less stable. Previous results in a narrow-gap approximation are extended to the case of a finite gap, and both axisymmetric and nonaxisymmetric disturbance modes are considered. The two-phase system becomes less stable as the finite gap tends to the narrow-gap limit. The two-phase system is more stable to nonaxisymmetric modes with azimuthal wavenumber n = 1; the stability of these n = 1 modes is sensitive to the latent heat of fusion.

Noncontact manipulation using a transversely magnetized rolling robot

NASA Astrophysics Data System (ADS)

Tung, Hsi-Wen; Peyer, Kathrin E.; Sargent, David F.; Nelson, Bradley J.

2013-09-01

A type of magnetic, wireless microrobot has been designed for non-contact manipulation of micro-objects in liquids. The agent, named the RodBot, has typical dimensions of 300 μm × 60 μm × 50 μm. The RodBot is transversely magnetized and rolls around its long axis on a surface in a rotating external magnetic field. In liquid environments, the RodBot generates a rising flow in front of it and a vortex above its body. The flow and vortex are efficient for picking-up and trapping micro-objects of sizes ranging from microns to one millimeter. In viscous solutions, a RodBot can transport objects many times its own size and weight.

Vortex dynamics during blade-vortex interactions

NASA Astrophysics Data System (ADS)

Peng, Di; Gregory, James W.

2015-05-01

Vortex dynamics during parallel blade-vortex interactions (BVIs) were investigated in a subsonic wind tunnel using particle image velocimetry (PIV). Vortices were generated by applying a rapid pitch-up motion to an airfoil through a pneumatic system, and the subsequent interactions with a downstream, unloaded target airfoil were studied. The blade-vortex interactions may be classified into three categories in terms of vortex behavior: close interaction, very close interaction, and collision. For each type of interaction, the vortex trajectory and strength variation were obtained from phase-averaged PIV data. The PIV results revealed the mechanisms of vortex decay and the effects of several key parameters on vortex dynamics, including separation distance (h/c), Reynolds number, and vortex sense. Generally, BVI has two main stages: interaction between vortex and leading edge (vortex-LE interaction) and interaction between vortex and boundary layer (vortex-BL interaction). Vortex-LE interaction, with its small separation distance, is dominated by inviscid decay of vortex strength due to pressure gradients near the leading edge. Therefore, the decay rate is determined by separation distance and vortex strength, but it is relatively insensitive to Reynolds number. Vortex-LE interaction will become a viscous-type interaction if there is enough separation distance. Vortex-BL interaction is inherently dominated by viscous effects, so the decay rate is dependent on Reynolds number. Vortex sense also has great impact on vortex-BL interaction because it changes the velocity field and shear stress near the surface.

Studies of the generation mechanisms of steady vortex formations in the channels of nuclear-power installations for purposes of improving the reliability and safety of their work

NASA Astrophysics Data System (ADS)

Mitrofanova, O.

2017-01-01

The analysis of the results of experimental researches on revealing the mechanisms of vortex formation in channels of complex geometry in the neutral and conductive media is carried out. The directions of researches related to the study of mechanisms of vortex generation and accumulation of energy by large-scale vortex structures are considered for the possibility of predictions of the man-made accidents and catastrophic natural phenomena. The main goal of ongoing investigations is the solution of the task aimed at improving the safety of nuclear power installations and, in particular, of the fast neutron reactors with liquid-metal coolants, and the prevention of emergency modes arising from acoustic, magnetic and hydrodynamic resonance effects.

Vortex with fourfold defect lines in a simple model of self-propelled particles

NASA Astrophysics Data System (ADS)

Seyed-Allaei, Hamid; Ejtehadi, Mohammad Reza

2016-03-01

We study the formation of a vortex with fourfold symmetry in a minimal model of self-propelled particles, confined inside a squared box, using computer simulations and also theoretical analysis. In addition to the vortex pattern, we observe five other regimes in the system: a homogeneous gaseous phase, band structures, moving clumps, moving clusters, and vibrating rings. All six regimes emerge from controlling the strength of noise and from the contribution of repulsion and alignment interactions. We study the shape of the vortex and its symmetry in detail. The pattern shows exponential defect lines where incoming and outgoing flows of particles collide. We show that alignment and repulsion interactions between particles are necessary to form such patterns. We derive hydrodynamical equations with an introduction of the "small deviation" technique to describe the vortex phase. The method is applicable to other systems as well. Finally, we compare the theory with the results of both computer simulations and an experiment using Quincke rotors. A good agreement between the three is observed.

Aircraft Wake Vortex Measurements at Denver International Airport

NASA Technical Reports Server (NTRS)

Dougherty, Robert P.; Wang, Frank Y.; Booth, Earl R.; Watts, Michael E.; Fenichel, Neil; D'Errico, Robert E.

2004-01-01

Airport capacity is constrained, in part, by spacing requirements associated with the wake vortex hazard. NASA's Wake Vortex Avoidance Project has a goal to establish the feasibility of reducing this spacing while maintaining safety. Passive acoustic phased array sensors, if shown to have operational potential, may aid in this effort by detecting and tracking the vortices. During August/September 2003, NASA and the USDOT sponsored a wake acoustics test at the Denver International Airport. The central instrument of the test was a large microphone phased array. This paper describes the test in general terms and gives an overview of the array hardware. It outlines one of the analysis techniques that is being applied to the data and gives sample results. The technique is able to clearly resolve the wake vortices of landing aircraft and measure their separation, height, and sinking rate. These observations permit an indirect estimate of the vortex circulation. The array also provides visualization of the vortex evolution, including the Crow instability.

Vortex-assisted magnetic β-cyclodextrin/attapulgite-linked ionic liquid dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography for the fast determination of four fungicides in water samples.

PubMed

Yang, Miyi; Xi, Xuefei; Wu, Xiaoling; Lu, Runhua; Zhou, Wenfeng; Zhang, Sanbing; Gao, Haixiang

2015-02-13

A novel microextraction technique combining magnetic solid-phase microextraction (MSPME) with ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) to determine four fungicides is presented in this work for the first time. The main factors affecting the extraction efficiency were optimized by the one-factor-at-a-time approach and the impacts of these factors were studied by an orthogonal design. Without tedious clean-up procedure, analytes were extracted from the sample to the adsorbent and organic solvent and then desorbed in acetonitrile prior to chromatographic analysis. Under the optimum conditions, good linearity and high enrichment factors were obtained for all analytes, with correlation coefficients ranging from 0.9998 to 1.0000 and enrichment factors ranging 135 and 159 folds. The recoveries for proposed approach were between 98% and 115%, the limits of detection were between 0.02 and 0.04 μg L(-1) and the RSDs changed from 2.96 to 4.16. The method was successfully applied in the analysis of four fungicides (azoxystrobin, chlorothalonil, cyprodinil and trifloxystrobin) in environmental water samples. The recoveries for the real water samples ranged between 81% and 109%. The procedure proved to be a time-saving, environmentally friendly, and efficient analytical technique. Copyright © 2015 Elsevier B.V. All rights reserved.

Relationship between lunar tidal enhancements in the equatorial electrojet and tropospheric eddy heat flux during stratospheric sudden warmings

NASA Astrophysics Data System (ADS)

Siddiqui, T. A.; Yamazaki, Y.; Stolle, C.; Lühr, H.; Matzka, J.

2017-12-01

A number of studies in recent years have reported about the lunar tidal enhancements in the equatorial electrojet (EEJ) from ground- and space-based magnetometer measurements during stratospheric sudden warming (SSW) events. In this study, we make use of the ground magnetometer recordings at Huancayo observatory in Peru for the years 1978 - 2013 to derive a relationship between the lunar tidal enhancements in the EEJ and tropospheric eddy heat fluxes at 100 hPa during the SSW events. Tropospheric eddy heat fluxes are used to quantify the amount of wave activity entering the stratosphere. Anomalously large upward wave activity is known to precede the polar vortex breakdown during SSWs. We make use of the superposed epoch analysis method to determine the temporal relations between lunar tidal enhancements and eddy heat flux anomalies during SSWs, in order to demonstrate the causal relationship between these two phenomena. We also compare the lunar tidal enhancements and eddy heat flux anomalies for vortex split and for vortex displaced SSWs. It is found that larger lunar tidal enhancements are recorded for vortex split events, as compared to vortex displaced events. This confirms earlier observation; larger heat flux anomalies are recorded during vortex split SSW events than the heat flux anomalies during vortex displaced SSW events. Further, the temporal relations of lunar tidal enhancements in the EEJ have been compared separately for both the QBO phases and with the phases of the moon with respect to the central epoch of SSWs by means of the superposed epoch analysis approach. The EEJ lunar tidal enhancements in the east phase of QBO are found to be larger than the lunar tidal enhancements in the west phase of QBO. The phase of moon relative to the central SSW epoch also affects the lunar tidal enhancement in the EEJ. It is found that the lunar tidal enhancements are significantly larger when the day of new or full moon lies near the central SSW epoch, as compared to cases when new or full moon occur further away from the central SSW epoch.

Vortex via process: analysis and mask fabrication for contact CDs <80 nm

NASA Astrophysics Data System (ADS)

Levenson, Marc D.; Tan, Sze M.; Dai, Grace; Morikawa, Yasutaka; Hayashi, Naoya; Ebihara, Takeaki

2003-06-01

In an optical vortex, the wavefront spirals like a corkscrew, rather than forming planes or spheres. Since any nonzero optical amplitude must have a well-defined phase, the axis of a vortex is always dark. Printed in negative resist at 248nm and NA=0.63, 250nm pitch vortex arrays would produce contact holes with 80nm0.6 can be patterned using a chromeless phase-edge mask composed of rectangles with nominal phases of 0°, 90°, 180° and 270°. Analytic and numerical calculations have been performed to characterize the aerial images projected from such vortex masks using the Kirchhoff-approximation and rigorous EMF methods. Combined with resist simulations, these analyses predict process windows with ~10%Elat and >200nm DOF for 80nm CDs on pitches greater than or equal to 250nm at σ greater than or equal to 0.15. Smaller CDs and pitches are possible with shorter wavelength and larger NA while larger pitches give rise to larger CDs. At pitch >0.8μm, the vortices begin to print independently for σ greater than or equal to 0.3. Such "independent" vortices have a quasi-isofocal dose that gives rise to 100nm contacts with Elat>9% and DOF>500nm at σ=0.3. The extra darkness of the nominal 270° phase step can be accommodated by fine-tuning the etch depth. A reticle fabrication process that achieves the required alignment and vertical wall profiles has been exercised and test masks analyzed. In an actual chip design, unwanted vortices and phase step images would be erased from the resist pattern by exposing the wafer with a second, more conventional trim mask. Vortex via placement is consistent with the coarse-gridded grating design paradigms which would - if widely exercised - lower the cost of the required reticles. Compared to other ways of producing deep sub-wavelength contacts, the vortex via process requires fewer masks and reduces the overlay and process control challenges. A high resolution negative-working resist process is essential, however.

Quench dynamics of the three-dimensional U(1) complex field theory: Geometric and scaling characterizations of the vortex tangle.

PubMed

Kobayashi, Michikazu; Cugliandolo, Leticia F

2016-12-01

We present a detailed study of the equilibrium properties and stochastic dynamic evolution of the U(1)-invariant relativistic complex field theory in three dimensions. This model has been used to describe, in various limits, properties of relativistic bosons at finite chemical potential, type II superconductors, magnetic materials, and aspects of cosmology. We characterize the thermodynamic second-order phase transition in different ways. We study the equilibrium vortex configurations and their statistical and geometrical properties in equilibrium at all temperatures. We show that at very high temperature the statistics of the filaments is the one of fully packed loop models. We identify the temperature, within the ordered phase, at which the number density of vortex lengths falls off algebraically and we associate it to a geometric percolation transition that we characterize in various ways. We measure the fractal properties of the vortex tangle at this threshold. Next, we perform infinite rate quenches from equilibrium in the disordered phase, across the thermodynamic critical point, and deep into the ordered phase. We show that three time regimes can be distinguished: a first approach toward a state that, within numerical accuracy, shares many features with the one at the percolation threshold; a later coarsening process that does not alter, at sufficiently low temperature, the fractal properties of the long vortex loops; and a final approach to equilibrium. These features are independent of the reconnection rule used to build the vortex lines. In each of these regimes we identify the various length scales of the vortices in the system. We also study the scaling properties of the ordering process and the progressive annihilation of topological defects and we prove that the time-dependence of the time-evolving vortex tangle can be described within the dynamic scaling framework.

Synchronized vortex shedding and sound radiation from two side-by-side rectangular cylinders of different cross-sectional aspect ratios

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

Octavianty, Ressa, E-mail: ressa-octavianty@ed.tmu.ac.jp; Asai, Masahito, E-mail: masai@tmu.ac.jp

Synchronized vortex shedding from two side-by-side cylinders and the associated sound radiation were examined experimentally at Reynolds numbers of the order of 10{sup 4} 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 squaremore » 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.« less

Vortex circulation and polarity patterns in closely packed cap arrays

DOE PAGES

Streubel, Robert; Kronast, Florian; Reiche, Christopher F.; ...

2016-01-25

For this work, we studied curvature-driven modifications to the magnetostatic coupling of vortex circulation and polarity in soft-magnetic closely packed cap arrays. A phase diagram for the magnetic remanent/transition states at room temperature as a function of diameter and thickness was assembled. For specimens with vortex remanent state (40 nm-thick Permalloy on 330 nm spherical nanoparticles), both vortex circulation and polarity were visualized. Intercap coupling upon vortex nucleation leads to the formation of vortex circulation patterns in closely packed arrays. The remanent circulation pattern can be tailored choosing the direction of the applied magnetic field with respect to the symmetrymore » axis of the hexagonal array. An even and random distribution of vortex polarity indicates the absence of any circulation-polarity coupling.« less

Phase-Field Simulations of Topological Structures and Topological Phase Transitions in Ferroelectric Oxide Heterostructures

NASA Astrophysics Data System (ADS)

Zijian Hong

Ferroelectrics are materials that exhibit spontaneous electric polarization which can be switched between energy-degenerated states by external stimuli (e.g., mechanical force and electric field) that exceeds a critical value. They have wide potential applications in memories, capacitors, piezoelectric and pyroelectric sensors, and nanomechanical systems. Topological structures and topological phase transitions have been introduced to the condensed matter physics in the past few decades and have attracted broad attentions in various disciplines due to the rich physical insights and broad potential applications. Ferromagnetic topological structures such as vortex and skyrmion are known to be stabilized by the antisymmetric chiral interaction (e.g., Dzyaloshinskii-Moriya interaction). Without such interaction, ferroelectric topological structures (i.e., vortex, flux-closure, skyrmions, and merons) have been studied only recently with other designing strategies, such as reducing the dimension of the ferroelectrics. The overarching goal of this dissertation is to investigate the topological structures in ferroelectric oxide perovskites as well as the topological phase transitions under external applied forces. Pb(Zr,Ti)O3 (PZT) with morphotropic phase boundary is widely explored for high piezoelectric and dielectric properties. The domain structure of PZT tetragonal/rhombohedral (T/R) bilayer is investigated. Strong interfacial coupling is shown, with large polarization rotation to a lower symmetry phase near the T/R interface. Interlayer domain growth can also be captured, with T-domains in the R layer and R-domains in the T layer. For thin PZT bilayer with 5nm of T-layer and 20 nm of R-layer, the a1/a 2 twin domain structure is formed in the top T layer, which could be fully switched to R domains under applied bias. While a unique flux-closure pattern is observed both theoretically and experimentally in the thick bilayer film with 50 nm of thickness for both T and R layers. It is revealed that the bilayer system could facilitate the motion of the ferroelastic adomain in the top T-layer since the a-domain is not directly embedded in the substrate with high density of defects which can pin the domain wall. Excellent dielectric and piezoelectric responses are demonstrated due to the large polarization rotation and the highly mobile domain walls in both the thick and thin bilayer systems. density of defects which can pin the domain wall. Excellent dielectric and piezoelectric responses are demonstrated due to the large polarization rotation and the highly mobile domain walls in both the thick and thin bilayer systems. The long-range ordered polar vortex array is observed in the (PbTiO 3)n/(SrTiO3)n (PTOn/STOn with n=10˜20) superlattices with combined experimental and theoretical studies. Phase-field simulations reveal the three-dimensional textures of the polar vortex arrays. The neighboring vortices rotate in the opposite directions, which extended into tube-like vortex lines perpendicular to the vortex plane. The thickness-dependent phase diagram is predicted and verified by experimental observations. The energetics (the contributions from elastic, electrostatic, gradient and Landau chemical energies) accompanying the phase transitions are analyzed in details. The dominating depolarization energy at short periodicity (n<10) favors a1/ a2 twin domain, while the large elastic relaxation and Landau energy reduction at large periodicity (n>20) leads to the formation of flux-closure domain with both 90° a/c domain walls and 180° c+/c - domain walls, counterbalancing of the individual energies at intermediate periodicities (n=10˜20) gives rise to the formation of exotic vortex structure with continuous polarization rotation surrounding a singularity-like vortex core. Analytical calculations are performed, showing that the stability of the polar vortex structure is directly related to the length of Pi times bulk domain wall width, where vortex structure can be expected when the geometric length scale of the ferroelectrics is close to this value. The role of insulating STO is further revealed, which shows that a rich phase diagram can be formed by simply tuning the thickness of this layer. Wave-like polar spiral phase is simulated by substituting part of the PTO with BiFeO3 (BFO) in the PTO/STO superlattice (i.e., in a (PTO) 4/(BFO)4/(PTO)4/(STO)12 tricolor system) which has demonstrate ordered polar vortex lattice. This spiral phase is made up of semi-vortex cores that are floating up-down in the ferroelectric PTO layers, giving rise to a net in-plane polarization. An increase of Curie temperature and topological to regular domain transition temperature (over 200 K) is observed, due to the higher Curie temperature and larger spontaneous polarization in BFO layers. This unidirectional spiral state can be reversibly switched by experimentally feasible in-plane field, which evolves into a metastable vortex structure in-between two spiral phases with opposite in-plane directions. (Abstract shortened by ProQuest.).

Correlation matching method for high-precision position detection of optical vortex using Shack-Hartmann wavefront sensor.

PubMed

Huang, Chenxi; Huang, Hongxin; Toyoda, Haruyoshi; Inoue, Takashi; Liu, Huafeng

2012-11-19

We propose a new method for realizing high-spatial-resolution detection of singularity points in optical vortex beams. The method uses a Shack-Hartmann wavefront sensor (SHWS) to record a Hartmanngram. A map of evaluation values related to phase slope is then calculated from the Hartmanngram. The position of an optical vortex is determined by comparing the map with reference maps that are calculated from numerically created spiral phases having various positions. Optical experiments were carried out to verify the method. We displayed various spiral phase distribution patterns on a phase-only spatial light modulator and measured the resulting singularity point using the proposed method. The results showed good linearity in detecting the position of singularity points. The RMS error of the measured position of the singularity point was approximately 0.056, in units normalized to the lens size of the lenslet array used in the SHWS.

Berry phase from vortex dynamics in BCS superconductors revisited

NASA Astrophysics Data System (ADS)

Tanaka, Akihiro; Machida, Masahiko

1999-02-01

Motivated by a recent series of papers by Ao et al., we reconsider the Berry phase produced by an adiabatic motion of a vortex in an s-wave BCS superconductor. Avoiding the use of the gradient expansion approach which may give rise to ambiguity in the presence of vortices, we make certain assumptions which enable us to extend the methods of Goff, Gaitan and Stone, originally used in the context of superfluid dynamics of 3He, to our vortex problem. Using the pseudo-spin representation of the BCS Hamiltonian, contributions to the Berry phase coming from each quasiparticle state constituting the ground state are added together to give a total phase proportional to n- C0, where n≡ {1}/{2}∑ pσ(1-ɛ/ ɛ 2+|Δ| 2) and C 0≡∑ pσΘ(-ɛ)=p 3F/3π 2 are the superconducting and normal electron densities, respectively. We consider this to be a clear counterexample to Ao's claim that the only possible hydrodynamic transverse force exerted on a vortex is a Magnus force proportional to n. Relations to the spectral-flow phenomenology of Volovik, and a brief discussion on possible extension to the cuprate superconductors, are suggested.

Combustion Science

NASA Image and Video Library

2003-04-01

This photograph depicts one of over thirty tests conducted on the Vortex Combustion Chamber Engine at Marshall Space Flight Center's (MSFC) test stand 115, a joint effort between NASA's MSFC and the U.S. Army AMCOM of Redstone Arsenal. The engine tests were conducted to evaluate an irnovative, "self-cooled", vortex combustion chamber, which relies on tangentially injected propellants from the chamber wall producing centrifugal forces that keep the relatively cold liquid propellants near the wall.

Investigation on filter method for smoothing spiral phase plate

NASA Astrophysics Data System (ADS)

Zhang, Yuanhang; Wen, Shenglin; Luo, Zijian; Tang, Caixue; Yan, Hao; Yang, Chunlin; Liu, Mincai; Zhang, Qinghua; Wang, Jian

2018-03-01

Spiral phase plate (SPP) for generating vortex hollow beams has high efficiency in various applications. However, it is difficult to obtain an ideal spiral phase plate because of its continuous-varying helical phase and discontinued phase step. This paper describes the demonstration of continuous spiral phase plate using filter methods. The numerical simulations indicate that different filter method including spatial domain filter, frequency domain filter has unique impact on surface topography of SPP and optical vortex characteristics. The experimental results reveal that the spatial Gaussian filter method for smoothing SPP is suitable for Computer Controlled Optical Surfacing (CCOS) technique and obtains good optical properties.

The Influence of Low-frequency Oscillation Propagation of the Tibetan Plateau Vortex on Rainstorm Downstream

NASA Astrophysics Data System (ADS)

Xiao, Tiangui; Wang, Chao; La, Jia; Du, Jun; Zhang, Kairong

2017-04-01

Based on Tibetan Plateau vortex data, ERA-Interim and NCEP/NCAR reanalysis data, the characteristics of Tibetan Plateau vortex and the relationship with Low-Frequency Oscillation (LFO) from 2003 to 2012 were investigated. The heavy rainstorm occurred in Sichuan from June 29th to July 2nd in 2013, caused by the LFO, was studied. Besides, the signal of LFO, energy transmission and those influence to rainstorm were also investigate. The main conclusions are as follows: (1)Most of Tibetan Plateau vortex generate in eastern plateau, located at Tanggula Mountains, Zaduo, Dege, Qumalai and Qaidam. The moving-out Tibetan Plateau vortex mainly generate in Qumalai and most vortex occurrences during April to September. There are three directions of moving-out vortex paths: northeast, southeast and east. The areas which plateau vortex moving into are mainly distributed in Gansu, Sichuan, Shaanxi and Ningxia. (2)The zonal wind at 500hPa in plateau key region has a significant main 10-30d oscillation, with the secondly significant oscillation in 30-50d and the third in 70-90d. The relative vorticity at 500hPa in plateau key region has a significant main 30-50d oscillations, with the secondly significant oscillation in 10-30d. The 30-50d oscillation phase zone with weak westerly oscillation zone of 500hPa, and the 10-30d oscillation positive phase zone with weak oscillation zone of 500hPa are benefit to vortex generation. The 30-50d oscillation of zonal wind at 500hPa provides necessary circulation background for generation of plateau vortex, and positive phase region of 10-30d oscillation of relative vorticity at 500hPa provide necessary dynamic background conditions for it. (3) Comparing with the high frequency oscillation vortex, 10-25d low-frequency vortex is not significant at 500hPa before merging into the basin vortex. However, after merging into the basin vortex, there is a significant relationship between low-frequency vortex and the process of development, weakening and disappearance during the basin rainstorm. A typical heavy rainstorm occurred in Sichuan was studied. In the horizontal direction，atmospheric disturbance energy transmit from the west Sichuan plateau to heavy rainfall areas in basin, that is indicating the low-frequency atmospheric disturbance energy transmission. In the vertical direction, the disturbance energy transfer to the downstream is probably the major reason caused this heavy rainstorm. The value of wave packet and disturbance energy indicates the difference stages of rainstorm. Key words: the tibetan plateau; plateau vortex; FLO; rainstorm; wave-packet Acknowledgements This study was supported by National Natural Science Foundation of China Fund Project (91337215, 41575066), National Key Basic Research Program (2013CB733206), Special Fund for Meteorological Research in the Public Interest (GYHY201406015), and Risk Assessment System of Significant Climate Events in Tibet (14H046).

Development of fast, efficient and ecological method employing vortex-assisted dispersive liquid-liquid microextraction combined with fast gas chromatography-mass spectrometry for pesticide residues analysis in alcohol-content samples.

PubMed

Hrouzková, Svetlana; Brišová, Mária; Szarka, Agneša

2017-07-14

A fast, ecological, and efficient method employing vortex-assisted dispersive liquid-liquid microextraction (DLLME) method for isolation and preconcentration of selected endocrine disrupting pesticides from beverages containing some degree of alcohol was developed. The effect of several extraction parameters, such as selection of extractive solvent, its volume and extraction time, the salt addition was investigated. Four different extractive solvents (chloroform, tetrachloroethane, tetrachloromethane and toluene) and their combinations were evaluated for DLLME. Under the following conditions: 1mL of fortified sample, 80μL of tetrachloroethane, 1.5mL of water, vortex assistance for 3min at the speed of 1800rpm, and no salt addition, the method was validated. Linearity was studied in the concentration range of 0.01-250μg/L with coefficient of correlation ranging between 0.9940 and 1.0000, limits of detection and quantification ranging between 0.02-1.4μg/L and 0.07-4.7μg/L, respectively. Recoveries were satisfactory in the range of 70-120%, with the exception of diphenyl, alachlor and fenarimol at the lowest concentration level and p,p-DDE at concentration level of 100 and 250μg/L. The applicability of the developed and validated method was proved by the analysis of real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

A technique for simultaneous detection of individual vortex states of Laguerre-Gaussian beams transmitted through an aqueous suspension of microparticles

NASA Astrophysics Data System (ADS)

Khonina, S. N.; Karpeev, S. V.; Paranin, V. D.

2018-06-01

A technique for simultaneous detection of individual vortex states of the beams propagating in a randomly inhomogeneous medium is proposed. The developed optical system relies on the correlation method that is invariant to the beam wandering. The intensity distribution formed at the optical system output does not require digital processing. The proposed technique based on a multi-order phase diffractive optical element (DOE) is studied numerically and experimentally. The developed detection technique is used for the analysis of Laguerre-Gaussian vortex beams propagating under conditions of intense absorption, reflection, and scattering in transparent and opaque microparticles in aqueous suspensions. The performed experimental studies confirm the relevance of the vortex phase dependence of a laser beam under conditions of significant absorption, reflection, and scattering of the light.

Elliptical vortex and oblique vortex lattice in the FeSe superconductor based on the nematicity and mixed superconducting orders

NASA Astrophysics Data System (ADS)

Lu, Da-Chuan; Lv, Yang-Yang; Li, Jun; Zhu, Bei-Yi; Wang, Qiang-Hua; Wang, Hua-Bing; Wu, Pei-Heng

2018-03-01

The electronic nematic phase is characterized as an ordered state of matter with rotational symmetry breaking, and has been well studied in the quantum Hall system and the high-Tc superconductors, regardless of cuprate or pnictide family. The nematic state in high-Tc systems often relates to the structural transition or electronic instability in the normal phase. Nevertheless, the electronic states below the superconducting transition temperature is still an open question. With high-resolution scanning tunneling microscope measurements, direct observation of vortex core in FeSe thin films revealed the nematic superconducting state by Song et al. Here, motivated by the experiment, we construct the extended Ginzburg-Landau free energy to describe the elliptical vortex, where a mixed s-wave and d-wave superconducting order is coupled to the nematic order. The nematic order induces the mixture of two superconducting orders and enhances the anisotropic interaction between the two superconducting orders, resulting in a symmetry breaking from C4 to C2. Consequently, the vortex cores are stretched into an elliptical shape. In the equilibrium state, the elliptical vortices assemble a lozenge-like vortex lattice, being well consistent with experimental results.

Large D-2 theory of superconducting fluctuations in a magnetic field and its application to iron pnictides.

PubMed

Murray, James M; Tesanović, Zlatko

2010-07-16

A Ginzburg-Landau approach to fluctuations of a layered superconductor in a magnetic field is used to show that the interlayer coupling can be incorporated within an interacting self-consistent theory of a single layer, in the limit of a large number of neighboring layers. The theory exhibits two phase transitions-a vortex liquid-to-solid transition is followed by a Bose-Einstein condensation into the Abrikosov lattice-illustrating the essential role of interlayer coupling. By using this theory, explicit expressions for magnetization, specific heat, and fluctuation conductivity are derived. We compare our results with recent experimental data on the iron-pnictide superconductors.

Thermocapillary convection of melts and its role in laser-plasma synthesis and laser-induced amorphism

NASA Astrophysics Data System (ADS)

Uglov, A. A.; Smurov, I. Iu.; Gus'kov, A. G.; Semakhin, S. A.

1987-06-01

The role of thermocapillary convection in mass transfer processes in melts is investigated analytically and experimentally using vacuum-arc melted Ni63-Ta37 and Cu50-Zr50 alloys. It is shown that thermocapillary convection not only leads to the transfer of alloying components to the deeper layers of the melt but also may produce, in certain cases, a significant temperature redistribution in the liquid phase. Convective transfer dominates over conduction when the product of Re and Pr is greater than 1. In the experiments, the structure of the amorphous and crystalline layers in the solidified alloys is found to be in qualitative agreement with the structure of a thermocapillary vortex.

Mesoscopic Vortex–Meissner currents in ring ladders

NASA Astrophysics Data System (ADS)

Haug, Tobias; Amico, Luigi; Dumke, Rainer; Kwek, Leong-Chuan

2018-07-01

Recent experimental progress have revealed Meissner and Vortex phases in low-dimensional ultracold atoms systems. Atomtronic setups can realize ring ladders, while explicitly taking the finite size of the system into account. This enables the engineering of quantized chiral currents and phase slips in between them. We find that the mesoscopic scale modifies the current. Full control of the lattice configuration reveals a reentrant behavior of Vortex and Meissner phases. Our approach allows a feasible diagnostic of the currents’ configuration through time-of-flight measurements.

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

Streubel, Robert; Kronast, Florian; Reiche, Christopher F.

For this work, we studied curvature-driven modifications to the magnetostatic coupling of vortex circulation and polarity in soft-magnetic closely packed cap arrays. A phase diagram for the magnetic remanent/transition states at room temperature as a function of diameter and thickness was assembled. For specimens with vortex remanent state (40 nm-thick Permalloy on 330 nm spherical nanoparticles), both vortex circulation and polarity were visualized. Intercap coupling upon vortex nucleation leads to the formation of vortex circulation patterns in closely packed arrays. The remanent circulation pattern can be tailored choosing the direction of the applied magnetic field with respect to the symmetrymore » axis of the hexagonal array. An even and random distribution of vortex polarity indicates the absence of any circulation-polarity coupling.« less

On the Scattering of Sound by a Rectilinear Vortex

NASA Astrophysics Data System (ADS)

HOWE, M. S.

1999-11-01

A re-examination is made of the two-dimensional interaction of a plane, time-harmonic sound wave with a rectilinear vortex of small core diameter at low Mach number. Sakov [1] and Ford and Smith [2] have independently resolved the “infinite forward scatter” paradox encountered in earlier applications of the Born approximation to this problem. The first order scattered field (Born approximation) has nulls in the forward and back scattering directions, but the interaction of the wave with non-acoustically compact components of the vortex velocity field causes wavefront distortion, and the phase of the incident wave to undergo a significant variation across a parabolic domain whose axis extends along the direction of forward scatter from the vortex core. The transmitted wave crests of the incident wave become concave and convex, respectively, on opposite sides of the axis of the parabola, and focusing and defocusing of wave energy produces corresponding increases and decreases in wave amplitude. Wave front curvature decreases with increasing distance from the vortex core, with the result that the wave amplitude and phase are asymptotically equal to the respective values they would have attained in the absence of the vortex. The transverse acoustic dipole generated by translational motion of the vortex at the incident wave acoustic particle velocity, and the interaction of the incident wave with acoustically compact components of the vortex velocity field, are responsible for a system of cylindrically spreading, scattered waves outside the parabolic domain.

Enhancement of superconductivity under pressure and the magnetic phase diagram of tantalum disulfide single crystals

PubMed Central

Abdel-Hafiez, M.; Zhao, X.-M.; Kordyuk, A. A.; Fang, Y.-W.; Pan, B.; He, Z.; Duan, C.-G.; Zhao, J.; Chen, X.-J.

2016-01-01

In low-dimensional electron systems, charge density waves (CDW) and superconductivity are two of the most fundamental collective quantum phenomena. For all known quasi-two-dimensional superconductors, the origin and exact boundary of the electronic orderings and superconductivity are still attractive problems. Through transport and thermodynamic measurements, we report on the field-temperature phase diagram in 2H-TaS2 single crystals. We show that the superconducting transition temperature (Tc) increases by one order of magnitude from temperatures at 0.98 K up to 9.15 K at 8.7 GPa when the Tc becomes very sharp. Additionally, the effects of 8.7 GPa illustrate a suppression of the CDW ground state, with critically small Fermi surfaces. Below the Tc the lattice of magnetic flux lines melts from a solid-like state to a broad vortex liquid phase region. Our measurements indicate an unconventional s-wave-like picture with two energy gaps evidencing its multi-band nature. PMID:27534898

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

Solis, Kyle J.; Martin, James E.

In recent years a rich variety of emergent phenomena have been observed when suspensions of magnetic particles are subjected to alternating magnetic fields. These particle assemblies often exhibit vigorous dynamics due to the injection of energy from the field. These include surface and interface phenomena, such as highly organized, segmented “snakes” that can be induced to swim by structural symmetry breaking, and “asters” and “anti-asters,” particle assemblies that can be manipulated to capture and transport cargo. In bulk suspensions of magnetic platelets subjected to multiaxial alternating fields, advection lattices and even vortex lattices have been created, and a variety ofmore » biomimetic dynamics – serpents, bees and amoebas – have been discovered in magnetic fluids suspended in an immiscible liquid. In this paper several new driven phases are presented, including flying chevrons, dense spinning clusters, filaments, and examples of phase coexistence in driven phases. These observations broaden the growing field of driven magnetic suspensions and present new challenges to those interested in simulating the dynamics of these complex systems.« less

Anomalous Josephson effect controlled by an Abrikosov vortex

NASA Astrophysics Data System (ADS)

Mironov, S.; Goldobin, E.; Koelle, D.; Kleiner, R.; Tamarat, Ph.; Lounis, B.; Buzdin, A.

2017-12-01

The possibility of a fast and precise Abrikosov vortex manipulation by a focused laser beam opens the way to create laser-driven Josephson junctions. We theoretically demonstrate that a vortex pinned in the vicinity of the Josephson junction generates an arbitrary ground state phase which can be equal not only to 0 or π but to any desired φ0 value in between. Such φ0 junctions have many peculiar properties and may be effectively controlled by the optically driven Abrikosov vortex. Also we theoretically show that the Josephson junction with the embedded vortex can serve as an ultrafast memory cell operating at sub THz frequencies.

Feasibility of wake vortex monitoring systems for air terminals

NASA Technical Reports Server (NTRS)

Wilson, D. J.; Shrider, K. R.; Lawrence, T. R.

1972-01-01

Wake vortex monitoring systems, especially those using laser Doppler sensors, were investigated. The initial phases of the effort involved talking with potential users (air traffic controllers, pilots, etc.) of a wake vortex monitoring system to determine system requirements from the user's viewpoint. These discussions involved the volumes of airspace to be monitored for vortices, and potential methods of using the monitored vortex data once the data are available. A subsequent task led to determining a suitable mathematical model of the vortex phenomena and developing a mathematical model of the laser Doppler sensor for monitoring the vortex flow field. The mathematical models were used in combination to help evaluate the capability of laser Doppler instrumentation in monitoring vortex flow fields both in the near vicinity of the sensor (within 1 kilometer and at long ranges(10 kilometers).

Universality of the Berezinskii-Kosterlitz-Thouless type of phase transition in the dipolar XY-model

NASA Astrophysics Data System (ADS)

Vasiliev, A. Yu; Tarkhov, A. E.; Menshikov, L. I.; Fedichev, P. O.; Fischer, Uwe R.

2014-05-01

We investigate the nature of the phase transition occurring in a planar XY-model spin system with dipole-dipole interactions. It is demonstrated that a Berezinskii-Kosterlitz-Thouless (BKT) type of phase transition always takes place at a finite temperature separating the ordered (ferro) and the disordered (para) phases. The low-temperature phase corresponds to an ordered state with thermal fluctuations, composed of a ‘gas’ of bound vortex-antivortex pairs, which would, when considered isolated, be characterized by a constant vortex-antivortex attraction force which is due to the dipolar interaction term in the Hamiltonian. Using a topological charge model, we show that small bound pairs are easily polarized, and screen the vortex-antivortex interaction in sufficiently large pairs. Screening changes the linear attraction potential of vortices to a logarithmic one, and leads to the familiar pair dissociation mechanism of the BKT type phase transition. The topological charge model is confirmed by numerical simulations, in which we demonstrate that the transition temperature slightly increases when compared with the BKT result for short-range interactions.

Universality in the Self Organized Critical behavior of a cellular model of superconducting vortex dynamics

NASA Astrophysics Data System (ADS)

Sun, Yudong; Vadakkan, Tegy; Bassler, Kevin

2007-03-01

We study the universality and robustness of variants of the simple model of superconducting vortex dynamics first introduced by Bassler and Paczuski in Phys. Rev. Lett. 81, 3761 (1998). The model is a coarse-grained model that captures the essential features of the plastic vortex motion. It accounts for the repulsive interaction between vortices, the pining of vortices at quenched disordered locations in the material, and the over-damped dynamics of the vortices that leads to tearing of the flux line lattice. We report the results of extensive simulations of the critical ``Bean state" dynamics of the model. We find a phase diagram containing four distinct phases of dynamical behavior, including two phases with distinct Self Organized Critical (SOC) behavior. Exponents describing the avalanche scaling behavior in the two SOC phases are determined using finite-size scaling. The exponents are found to be robust within each phase and for different variants of the model. The difference of the scaling behavior in the two phases is also observed in the morphology of the avalanches.

Status on Technology Development of Optic Fiber-Coupled Laser Ignition System for Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Trinh, Huu P.; Early, Jim; Osborne, Robin; Thomas, Matthew; Bossard, John

2003-01-01

To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for liquid rocket engine applications. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concept: not only offer system simplicity, but also enhance the combustion performance. Test results have shown that chamber performance is markedly high even at a low chamber length-to-diameter ratio. This incentive can be translated to a convenience in the thrust chamber packaging.

Reconstructing a plasmonic metasurface for a broadband high-efficiency optical vortex in the visible frequency.

PubMed

Lu, Bing-Rui; Deng, Jianan; Li, Qi; Zhang, Sichao; Zhou, Jing; Zhou, Lei; Chen, Yifang

2018-06-14

Metasurfaces consisting of a two-dimensional metallic nano-antenna array are capable of transferring a Gaussian beam into an optical vortex with a helical phase front and a phase singularity by manipulating the polarization/phase status of light. This miniaturizes a laboratory scaled optical system into a wafer scale component, opening up a new area for broad applications in optics. However, the low conversion efficiency to generate a vortex beam from circularly polarized light hinders further development. This paper reports our recent success in improving the efficiency over a broad waveband at the visible frequency compared with the existing work. The choice of material, the geometry and the spatial organization of meta-atoms, and the fabrication fidelity are theoretically investigated by the Jones matrix method. The theoretical conversion efficiency over 40% in the visible wavelength range is worked out by systematic calculation using the finite difference time domain (FDTD) method. The fabricated metasurface based on the parameters by theoretical optimization demonstrates a high quality vortex in optical frequencies with a significantly enhanced efficiency of over 20% in a broad waveband.

Microphysical Modelling of the 1999-2000 Arctic Winter. 3; Impact of Homogeneous Freezing on PSCs

NASA Technical Reports Server (NTRS)

Drdla, K.

2003-01-01

Simulations of the 1999-2000 winter have tested the effect on polar stratospheric clouds (PSCs) of the homogeneous freezing of liquid ternary solutions into nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD). Proposed laboratory-derived volume-based and surface-based homogeneous freezing rates have both been examined, including different assumptions about the extrapolation of laboratory measurements to atmospheric conditions. Widespread PSC formation and denitrification are possible in several of the scenarios examined. However, the simulations are all unable to explain the solid-phase PSCs observed early in the 1999-2000 winter, and are unable to reproduce the measured extent of vortex denitrification. These problems can both be attributed to the relatively cold temperatures, more than 5 K below the NAT condensation point, necessary for effective homogeneous freezing. Therefore synoptic-scale homogeneous freezing appears unlikely to be the primary mechanism responsible for solid-phase PSC formation.

Storage and retrieval of vector beams of light in a multiple-degree-of-freedom quantum memory.

PubMed

Parigi, Valentina; D'Ambrosio, Vincenzo; Arnold, Christophe; Marrucci, Lorenzo; Sciarrino, Fabio; Laurat, Julien

2015-07-13

The full structuration of light in the transverse plane, including intensity, phase and polarization, holds the promise of unprecedented capabilities for applications in classical optics as well as in quantum optics and information sciences. Harnessing special topologies can lead to enhanced focusing, data multiplexing or advanced sensing and metrology. Here we experimentally demonstrate the storage of such spatio-polarization-patterned beams into an optical memory. A set of vectorial vortex modes is generated via liquid crystal cell with topological charge in the optic axis distribution, and preservation of the phase and polarization singularities is demonstrated after retrieval, at the single-photon level. The realized multiple-degree-of-freedom memory can find applications in classical data processing but also in quantum network scenarios where structured states have been shown to provide promising attributes, such as rotational invariance.

Storage and retrieval of vector beams of light in a multiple-degree-of-freedom quantum memory

PubMed Central

Parigi, Valentina; D'Ambrosio, Vincenzo; Arnold, Christophe; Marrucci, Lorenzo; Sciarrino, Fabio; Laurat, Julien

2015-01-01

The full structuration of light in the transverse plane, including intensity, phase and polarization, holds the promise of unprecedented capabilities for applications in classical optics as well as in quantum optics and information sciences. Harnessing special topologies can lead to enhanced focusing, data multiplexing or advanced sensing and metrology. Here we experimentally demonstrate the storage of such spatio-polarization-patterned beams into an optical memory. A set of vectorial vortex modes is generated via liquid crystal cell with topological charge in the optic axis distribution, and preservation of the phase and polarization singularities is demonstrated after retrieval, at the single-photon level. The realized multiple-degree-of-freedom memory can find applications in classical data processing but also in quantum network scenarios where structured states have been shown to provide promising attributes, such as rotational invariance. PMID:26166257

Numerical Simulations of Instabilities in Single-Hole Office Elements

NASA Technical Reports Server (NTRS)

Ahuja, Vineet; Hosangadi, Ashvin; Hitt, Matthew A.; Lineberry, David M.

2013-01-01

An orifice element is commonly used in liquid rocket engine test facilities either as a flow metering device, a damper for acoustic resonance or to provide a large reduction in pressure over a very small distance in the piping system. While the orifice as a device is largely effective in stepping down pressure, it is also susceptible to a wake-vortex type instability that generates pressure fluctuations that propagate downstream and interact with other elements of the test facility resulting in structural vibrations. Furthermore in piping systems an unstable feedback loop can exist between the vortex shedding and acoustic perturbations from upstream components resulting in an amplification of the modes convecting downstream. Such was the case in several tests conducted at NASA as well as in the Ariane 5 strap-on P230 engine in a static firing test where pressure oscillations of 0.5% resulted in 5% thrust oscillations. Exacerbating the situation in cryogenic test facilities, is the possibility of the formation of vapor clouds when the pressure in the wake falls below the vapor pressure leading to a cavitation instability that has a lower frequency than the primary wake-vortex instability. The cavitation instability has the potential for high amplitude fluctuations that can cause catastrophic damage in the facility. In this paper high-fidelity multi-phase numerical simulations of an orifice element are used to characterize the different instabilities, understand the dominant instability mechanisms and identify the tonal content of the instabilities.

Vortex algebra by multiply cascaded four-wave mixing of femtosecond optical beams.

PubMed

Hansinger, Peter; Maleshkov, Georgi; Garanovich, Ivan L; Skryabin, Dmitry V; Neshev, Dragomir N; Dreischuh, Alexander; Paulus, Gerhard G

2014-05-05

Experiments performed with different vortex pump beams show for the first time the algebra of the vortex topological charge cascade, that evolves in the process of nonlinear wave mixing of optical vortex beams in Kerr media due to competition of four-wave mixing with self-and cross-phase modulation. This leads to the coherent generation of complex singular beams within a spectral bandwidth larger than 200nm. Our experimental results are in good agreement with frequency-domain numerical calculations that describe the newly generated spectral satellites.

Direct emission of chirality controllable femtosecond LG01 vortex beam

NASA Astrophysics Data System (ADS)

Wang, S.; Zhang, S.; Yang, H.; Xie, J.; Jiang, S.; Feng, G.; Zhou, S.

2018-05-01

Direct emission of a chirality controllable ultrafast LG01 mode vortex optical beam from a conventional z-type cavity design SESAM (SEmiconductor Saturable Absorber Mirror) mode locked LD pumped Yb:Phosphate laser has been demonstrated. A clean 360 fs vortex beam of ˜45.7 mW output power has been achieved. A radial shear interferometer has been built to determine the phase singularity and the wavefront helicity of the ultrafast output laser. Theoretically, it is found that the LG01 vortex beam is obtained via the combination effect of diagonal HG10 mode generation by off-axis pumping and the controllable Gouy phase difference between HG10 and HG01 modes in the sagittal and tangential planes. The chirality of the LG01 mode can be manipulated by the pump position to the original point of the laser cavity optical axis.

Interactions and scattering of quantum vortices in a polariton fluid.

PubMed

Dominici, Lorenzo; Carretero-González, Ricardo; Gianfrate, Antonio; Cuevas-Maraver, Jesús; Rodrigues, Augusto S; Frantzeskakis, Dimitri J; Lerario, Giovanni; Ballarini, Dario; De Giorgi, Milena; Gigli, Giuseppe; Kevrekidis, Panayotis G; Sanvitto, Daniele

2018-04-13

Quantum vortices, the quantized version of classical vortices, play a prominent role in superfluid and superconductor phase transitions. However, their exploration at a particle level in open quantum systems has gained considerable attention only recently. Here we study vortex pair interactions in a resonant polariton fluid created in a solid-state microcavity. By tracking the vortices on picosecond time scales, we reveal the role of nonlinearity, as well as of density and phase gradients, in driving their rotational dynamics. Such effects are also responsible for the split of composite spin-vortex molecules into elementary half-vortices, when seeding opposite vorticity between the two spinorial components. Remarkably, we also observe that vortices placed in close proximity experience a pull-push scenario leading to unusual scattering-like events that can be described by a tunable effective potential. Understanding vortex interactions can be useful in quantum hydrodynamics and in the development of vortex-based lattices, gyroscopes, and logic devices.

Chevrons, filaments, spinning clusters and phase coexistence: emergent dynamics of 2- and 3-d particle suspensions driven by multiaxial magnetic fields

DOE PAGES

Solis, Kyle J.; Martin, James E.

2017-07-06

In recent years a rich variety of emergent phenomena have been observed when suspensions of magnetic particles are subjected to alternating magnetic fields. These particle assemblies often exhibit vigorous dynamics due to the injection of energy from the field. These include surface and interface phenomena, such as highly organized, segmented “snakes” that can be induced to swim by structural symmetry breaking, and “asters” and “anti-asters,” particle assemblies that can be manipulated to capture and transport cargo. In bulk suspensions of magnetic platelets subjected to multiaxial alternating fields, advection lattices and even vortex lattices have been created, and a variety ofmore » biomimetic dynamics – serpents, bees and amoebas – have been discovered in magnetic fluids suspended in an immiscible liquid. In this paper several new driven phases are presented, including flying chevrons, dense spinning clusters, filaments, and examples of phase coexistence in driven phases. These observations broaden the growing field of driven magnetic suspensions and present new challenges to those interested in simulating the dynamics of these complex systems.« less

Afterlife of a Drop Impacting a Liquid Pool

NASA Astrophysics Data System (ADS)

Saha, Abhishek; Wei, Yanju; Tang, Xiaoyu; Law, Chung K.

2017-11-01

Drop impact on liquid pool is ubiquitous in industrial processes, such as inkjet printing and spray coating. While merging of drop with the impacted liquid surface is essential to facilitate the printing and coating processes, it is the afterlife of this merged drop and associated mixing which control the quality of the printed or coated surface. In this talk we will report an experimental study on the structural evolution of the merged droplet inside the liquid pool. First, we will analyze the depth of the crater created on the pool surface by the impacted drop for a range of impact inertia, and we will derive a scaling relation and the associated characteristic time-scale. Next, we will focus on the toroidal vortex formed by the moving drop inside the liquid pool and assess the characteristic time and length scales of the penetration process. The geometry of the vortex structure which qualitatively indicates the degree of mixedness will also be discussed. Finally, we will present the results from experiments with various viscosities to demonstrate the role of viscous dissipation on the geometry and structure formed by the drop. This work is supported by the Army Research Office and the Xerox Corporation.

Vortex shedding flow meter performance at high flow velocities

NASA Technical Reports Server (NTRS)

Siegwarth, J. D.

1986-01-01

In some of the ducts of the Space Shuttle Main Engine (SSME), the maximum liquid oxygen flow velocities approach 10 times those at which liquid flow measurements are normally made. The hydrogen gas flow velocities in other ducts exceed the maximum for gas flow measurement by more than a factor of 3. The results presented here show from water flow tests that vortex shedding flow meters of the appropriate design can measure water flow to velocities in excess of 55 m/s, which is a Reynolds number of about 2 million. Air flow tests have shown that the same meter can measure flow to a Reynolds number of at least 22 million. Vortex shedding meters were installed in two of the SSME ducts and tested with water flow. Narrow spectrum lines were obtained and the meter output frequencies were proportional to flow to + or - 0.5% or better over the test range with no flow conditioning, even though the ducts had multiple bends preceeding the meter location. Meters with the shedding elements only partially spanning the pipe and some meters with ring shaped shedding elements were also tested.

Vortex Domain Structure in Ferroelectric Nanoplatelets and Control of its Transformation by Mechanical Load

PubMed Central

Chen, W. J.; Zheng, Yue; Wang, Biao

2012-01-01

Vortex domain patterns in low-dimensional ferroelectrics and multiferroics have been extensively studied with the aim of developing nanoscale functional devices. However, control of the vortex domain structure has not been investigated systematically. Taking into account effects of inhomogeneous electromechanical fields, ambient temperature, surface and size, we demonstrate significant influence of mechanical load on the vortex domain structure in ferroelectric nanoplatelets. Our analysis shows that the size and number of dipole vortices can be controlled by mechanical load, and yields rich temperature-stress (T-S) phase diagrams. Simulations also reveal that transformations between “vortex states” induced by the mechanical load are possible, which is totally different from the conventional way controlled on the vortex domain by the electric field. These results are relevant to application of vortex domain structures in ferroelectric nanodevices, and suggest a novel route to applications including memories, mechanical sensors and transducers. PMID:23150769

The Effect of Pitching Phase on the Vortex Circulation for a Flapping Wing During Stroke Reversal

NASA Astrophysics Data System (ADS)

Burge, Matthew; Ringuette, Matthew

2017-11-01

We study the effect of pitching-phase on the circulation behavior for the 3D flow structures produced during stroke reversal for a 2-degree-of-freedom flapping wing executing hovering kinematics. Previous research has related the choice in pitching-phase with respect to the wing rotation during stroke reversal (advanced vs. symmetric pitch-timing) to a lift peak preceding stroke reversal. However, results from experiments on the time-varying circulation contributions from the 3D vortex structures across the span produced by both rotation and pitching are lacking. The objective of this research is to quantitatively examine how the spanwise circulation of these structures is affected by the pitching-phase for several reduced pitching frequencies. We employ a scaled wing model in a glycerin-water mixture and measure the time-varying velocity using multiple planes of stereo digital particle image velocimetry. Data-plane positions along the wing span are informed by the unsteady behavior of the 3D vortex structures found in our prior flow visualization movies. Individual vortices are identified to calculate their circulation. This work is aimed at understanding how the behavior of the vortex structures created during stroke reversal vary with key motion parameters. This work is supported by the National Science Foundation, Award Number 1336548, supervised by Dr. Ronald Joslin.

Determination of phthalate esters in distillates by ultrasound-vortex-assisted dispersive liquid-liquid micro-extraction (USVADLLME) coupled with gas chromatography/mass spectrometry.

PubMed

Montevecchi, Giuseppe; Masino, Francesca; Zanasi, Luca; Antonelli, Andrea

2017-04-15

A method for the extraction of phthalate esters (PAEs) by Ultrasound-Vortex-Assisted Dispersive Liquid-Liquid Micro-Extraction (USVADLLME) approach was optimised and applied for the first time to a historical series of brandies. These contaminants are widely spread in the environment as a consequence of about half century of use in different fields of applications. The concern about these substances and the recent legal restrictions of China in distillates import need a quick and sensitive method for their quantification. The proposed method, moreover, is environmentally oriented due to the disposal of micro-quantities of solvent required. In fact, sub-ppm-limits of detection were achieved with a solvent volume as low as 160μL. The analysed samples were within the legal limits, except for some very ancient brandies whose contamination was probably due to a PAEs concentration effect as a consequence of long ageing and for the use of plastic pipelines no more operative. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hollow vortex Gaussian beams

NASA Astrophysics Data System (ADS)

Zhou, GuoQuan; Cai, YangJian; Dai, ChaoQing

2013-05-01

A kind of hollow vortex Gaussian beam is introduced. Based on the Collins integral, an analytical propagation formula of a hollow vortex Gaussian beam through a paraxial ABCD optical system is derived. Due to the special distribution of the optical field, which is caused by the initial vortex phase, the dark region of a hollow vortex Gaussian beam will not disappear upon propagation. The analytical expressions for the beam propagation factor, the kurtosis parameter, and the orbital angular momentum density of a hollow vortex Gaussian beam passing through a paraxial ABCD optical system are also derived, respectively. The beam propagation factor is determined by the beam order and the topological charge. The kurtosis parameter and the orbital angular momentum density depend on beam order n, topological charge m, parameter γ, and transfer matrix elements A and D. As a numerical example, the propagation properties of a hollow vortex Gaussian beam in free space are demonstrated. The hollow vortex Gaussian beam has eminent propagation stability and has crucial application prospects in optical micromanipulation.

Excitation of high density surface plasmon polariton vortex array

NASA Astrophysics Data System (ADS)

Kuo, Chun-Fu; Chu, Shu-Chun

2018-06-01

This study proposes a method to excite surface plasmon polariton (SPP) vortex array of high spatial density on metal/air interface. A doughnut vector beam was incident at four rectangularly arranged slits to excite SPP vortex array. The doughnut vector beam used in this study has the same field intensity distribution as the regular doughnut laser mode, TEM01* mode, but a different polarization distribution. The SPP vortex array is achieved through the matching of both polarization state and phase state of the incident doughnut vector beam with the four slits. The SPP field distribution excited in this study contains stable array-distributed time-varying optical vortices. Theoretical derivation, analytical calculation and numerical simulation were used to discuss the characteristics of the induced SPP vortex array. The period of the SPP vortex array induced by the proposed method had only half SPPs wavelength. In addition, the vortex number in an excited SPP vortex array can be increased by enlarging the structure.

Extraction and preconcentration of trace Al and Cr from vegetable samples by vortex-assisted ionic liquid-based dispersive liquid-liquid microextraction prior to atomic absorption spectrometric determination.

PubMed

Altunay, Nail; Yıldırım, Emre; Gürkan, Ramazan

2018-04-15

In the study, a simple, and efficient microextraction approach, which is termed as vortex-assisted ionic liquid-based dispersive liquid-liquid microextraction (VA-IL-DLLME), was developed for flame atomic absorption spectrometric analysis of aluminum (Al) and chromium (Cr) in vegetables. The method is based on the formation of anionic chelate complexes of Al(III) and Cr(VI) with o-hydroxy azo dye, at pH 6.5, and then extraction of the hydrophobic ternary complexes formed in presence of cetyltrimethylammonium bromide (CTAB) into a 125 μL volume of 1-butyl-3-methylimidazolium bis(trifluorosulfonyl)imide [C 4 mim][Tf 2 N]) as extraction solvent. Under optimum conditions, the detection limits were 0.02 µg L -1 in linear working range of 0.07-100 µg L -1 for Al(III), and 0.05 µg L -1 in linear working range of 0.2-80 µg L -1 for Cr(VI). After the validation by analysis of a certified reference material (CRM), the method was successfully applied to the determination of Al and Cr in vegetables using standard addition method. Copyright © 2017 Elsevier Ltd. All rights reserved.

Design, fabrication, and measurement of reflective metasurface for orbital angular momentum vortex wave in radio frequency domain

NASA Astrophysics Data System (ADS)

Yu, Shixing; Li, Long; Shi, Guangming; Zhu, Cheng; Zhou, Xiaoxiao; Shi, Yan

2016-03-01

In this paper, a reflective metasurface is designed, fabricated, and experimentally demonstrated to generate an orbital angular momentum (OAM) vortex wave in radio frequency domain. Theoretical formula of phase-shift distribution is deduced and used to design the metasurface producing vortex radio waves. The prototype of a practical configuration is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that the vortex waves with different OAM mode numbers can be flexibly generated by using sub-wavelength reflective metasurfaces. The proposed method and metasurface pave a way to generate the OAM vortex waves for radio and microwave wireless communication applications.

Glassiness versus Order in Densely Frustrated Josephson Arrays

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

Gupta, P.; Teitel, S.; Gingras, M.J.

1998-01-01

We carry out extensive Monte Carlo simulations of the Coulomb gas dual to the uniformly frustrated two-dimensional XY model, for a sequence of frustrations f converging to the irrational (3{minus}{radical}(5))/ 2. We find in these systems a sharp first order equilibrium phase transition to an ordered vortex structure at a T{sub c} which varies only slightly with f . This ordered vortex structure remains, in general, phase incoherent until a lower vortex pinning transition T{sub p}(f) that varies with f. We argue that the glassy behaviors reported for this model in earlier simulations are dynamic effects. {copyright} {ital 1997} {italmore » The American Physical Society}« less

A polyphonic acoustic vortex and its complementary chords

NASA Astrophysics Data System (ADS)

Wilson, C.; Padgett, M. J.

2010-02-01

Using an annular phased array of eight loudspeakers, we generate sound beams that simultaneously contain phase singularities at a number of different frequencies. These frequencies correspond to different musical notes and the singularities can be set to overlap along the beam axis, creating a polyphonic acoustic vortex. Perturbing the drive amplitudes of the speakers means that the singularities no longer overlap, each note being nulled at a slightly different lateral position, where the volume of the other notes is now nonzero. The remaining notes form a tri-note chord. We contrast this acoustic phenomenon to the optical case where the perturbation of a white light vortex leads to a spectral spatial distribution.

Three-dimensional imaging of vortex structure in a ferroelectric nanoparticle driven by an electric field.

PubMed

Karpov, D; Liu, Z; Rolo, T Dos Santos; Harder, R; Balachandran, P V; Xue, D; Lookman, T; Fohtung, E

2017-08-17

Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. Here, we utilize Bragg coherent diffractive imaging of a single BaTiO 3 nanoparticle in a composite polymer/ferroelectric capacitor to study the behavior of a three-dimensional vortex formed due to competing interactions involving ferroelectric domains. Our investigation of the structural phase transitions under the influence of an external electric field shows a mobile vortex core exhibiting a reversible hysteretic transformation path. We also study the toroidal moment of the vortex under the action of the field. Our results open avenues for the study of the structure and evolution of polar vortices and other topological structures in operando in functional materials under cross field configurations.Imaging of topological states of matter such as vortex configurations has generally been limited to 2D surface effects. Here Karpov et al. study the volumetric structure and dynamics of a vortex core mediated by electric-field induced structural phase transition in a ferroelectric BaTiO 3 nanoparticle.

High fidelity phase locked PIV measurements analysing the flow fields surrounding an oscillating piezoelectric fan

NASA Astrophysics Data System (ADS)

Jeffers, Nicholas; Nolan, Kevin; Stafford, Jason; Donnelly, Brian

2014-07-01

Piezoelectric fans have been studied extensively and are seen as a promising technology for thermal management due to their ability to provide quiet, reliable cooling with low power consumption. The fluid mechanics of an unconfined piezoelectric fan are complex which is why the majority of the literature to date confines the fan in an attempt to simplify the flow field. This paper investigates the fluid mechanics of an unconfined fan operating in its first vibration frequency mode. The piezoelectric fan used in this study measures 12.7mm × 70mm and resonates at 92.5Hz in air. A custom built experimental facility was developed to capture the fan's flow field using phase locked Particle Image Velocimetry (PIV). The phase locked PIV results are presented in terms of vorticity and show the formation of a horse shoe vortex. A three dimensional A2 criterion constructed from interpolated PIV measurements was used to identify the vortex core in the vicinity of the fan. This analysis was used to clearly identify the formation of a horse shoe vortex that turns into a hairpin vortex before it breaks up due to a combination of vortex shedding and flow along the fan blade. The results presented in this paper contribute to both the fluid dynamics and heat transfer literature concerning first mode fan oscillation.

Effects of large-scale wind driven turbulence on sound propagation

NASA Technical Reports Server (NTRS)

Noble, John M.; Bass, Henry E.; Raspet, Richard

1990-01-01

Acoustic measurements made in the atmosphere have shown significant fluctuations in amplitude and phase resulting from the interaction with time varying meteorological conditions. The observed variations appear to have short term and long term (1 to 5 minutes) variations at least in the phase of the acoustic signal. One possible way to account for this long term variation is the use of a large scale wind driven turbulence model. From a Fourier analysis of the phase variations, the outer scales for the large scale turbulence is 200 meters and greater, which corresponds to turbulence in the energy-containing subrange. The large scale turbulence is assumed to be elongated longitudinal vortex pairs roughly aligned with the mean wind. Due to the size of the vortex pair compared to the scale of the present experiment, the effect of the vortex pair on the acoustic field can be modeled as the sound speed of the atmosphere varying with time. The model provides results with the same trends and variations in phase observed experimentally.

Low energy consumption vortex wave flow membrane bioreactor.

PubMed

Wang, Zhiqiang; Dong, Weilong; Hu, Xiaohong; Sun, Tianyu; Wang, Tao; Sun, Youshan

2017-11-01

In order to reduce the energy consumption and membrane fouling of the conventional membrane bioreactor (MBR), a kind of low energy consumption vortex wave flow MBR was exploited based on the combination of biofilm process and membrane filtration process, as well as the vortex wave flow technique. The experimental results showed that the vortex wave flow state in the membrane module could be formed when the Reynolds number (Re) of liquid was adjusted between 450 and 1,050, and the membrane flux declined more slowly in the vortex wave flow state than those in the laminar flow state and turbulent flow state. The MBR system was used to treat domestic wastewater under the condition of vortex wave flow state for 30 days. The results showed that the removal efficiency for CODcr and NH 3 -N was 82% and 98% respectively, and the permeate quality met the requirement of 'Water quality standard for urban miscellaneous water consumption (GB/T 18920-2002)'. Analysis of the energy consumption of the MBR showed that the average energy consumption was 1.90 ± 0.55 kWh/m 3 (permeate), which was only two thirds of conventional MBR energy consumption.

Fractional Fourier transform of Lorentz-Gauss vortex beams

NASA Astrophysics Data System (ADS)

Zhou, GuoQuan; Wang, XiaoGang; Chu, XiuXiang

2013-08-01

An analytical expression for a Lorentz-Gauss vortex beam passing through a fractional Fourier transform (FRFT) system is derived. The influences of the order of the FRFT and the topological charge on the normalized intensity distribution, the phase distribution, and the orbital angular momentum density of a Lorentz-Gauss vortex beam in the FRFT plane are examined. The order of the FRFT controls the beam spot size, the orientation of the beam spot, the spiral direction of the phase distribution, the spatial orientation of the two peaks in the orbital angular momentum density distribution, and the magnitude of the orbital angular momentum density. The increase of the topological charge not only results in the dark-hollow region becoming large, but also brings about detail changes in the beam profile. The spatial orientation of the two peaks in the orbital angular momentum density distribution and the phase distribution also depend on the topological charge.

Measurement of the topological charge and index of vortex vector optical fields with a space-variant half-wave plate.

PubMed

Liu, Gui-Geng; Wang, Ke; Lee, Yun-Han; Wang, Dan; Li, Ping-Ping; Gou, Fangwang; Li, Yongnan; Tu, Chenghou; Wu, Shin-Tson; Wang, Hui-Tian

2018-02-15

Vortex vector optical fields (VVOFs) refer to a kind of vector optical field with an azimuth-variant polarization and a helical phase, simultaneously. Such a VVOF is defined by the topological index of the polarization singularity and the topological charge of the phase vortex. We present a simple method to measure the topological charge and index of VVOFs by using a space-variant half-wave plate (SV-HWP). The geometric phase grating of the SV-HWP diffracts a VVOF into ±1 orders with orthogonally left- and right-handed circular polarizations. By inserting a polarizer behind the SV-HWP, the two circular polarization states project into the linear polarization and then interfere with each other to form the interference pattern, which enables the direct measurement of the topological charge and index of VVOFs.

Current induced vortex wall dynamics in helical magnetic systems

NASA Astrophysics Data System (ADS)

Roostaei, Bahman

2015-03-01

Nontrivial topology of interfaces separating phases with opposite chirality in helical magnetic metals result in new effects as they interact with spin polarized current. These interfaces or vortex walls consist of a one dimensional array of vortex lines. We predict that adiabatic transfer of angular momentum between vortex array and spin polarized current will result in topological Hall effect in multi-domain samples. Also we predict that the motion of the vortex array will result in a new damping mechanism for magnetic moments based on Lenz's law. We study the dynamics of these walls interacting with electric current and use fundamental electromagnetic laws to quantify those predictions. On the other hand discrete nature of vortex walls affects their pinning and results in low depinning current density. We predict the value of this current using collective pinning theory.

Characterization of quantum vortex dynamics in superfluid helium

NASA Astrophysics Data System (ADS)

Meichle, David P.

Liquid helium obtains superfluid properties when cooled below the Lambda transition temperature of 2.17 K. A superfluid, which is a partial Bose Einstein condensate, has many exotic properties including free flow without friction, and ballistic instead of diffusive heat transport. A superfluid is also uniquely characterized by the presence of quantized vortices, dynamical line-like topological phase defects around which all circulation in the flow is constrained. Two vortices can undergo a violent process called reconnection when they approach, cross, and retract having exchanged tails. With a numerical examination of a local, linearized solution near reconnection we discovered a dynamically unstable stationary solution to the Gross-Pitaevskii equation, which was relaxed to a fully non-linear solution using imaginary time propagation. This investigation explored vortex reconnection in the context of the changing topology of the order parameter, a complex field governing the superfluid dynamics at zero temperature. The dynamics of the vortices can be studied experimentally by dispersing tracer particles into a superfluid flow and recording their motions with movie cameras. The pioneering work of Bewley et al. provided the first visualization technique using frozen gases to create tracer particles. Using this technique, we experimentally observed for the first time the excitation of helical traveling waves on a vortex core called Kelvin waves. Kelvin waves are thought to be a central mechanism for dissipation in this inviscid fluid, as they provide an efficient cascade mechanism for transferring energy from large to microscopic length scales. We examined the Kelvin waves in detail, and compared their dynamics in fully self-similar non-dimensional coordinates to theoretical predictions. Additionally, two experimental advances are presented. A newly invented technique for reliably dispersing robust, nanometer-scale fluorescent tracer particles directly into the superfluid is described. A detailed numerical investigation of the particle-vortex interactions provides novel calculations of the force trapping particles on vortices, and a scaling was found suggesting that smaller particles may remain bound to the vortices at much higher speeds than larger particles. Lastly, a new stereographic imaging system has been developed, allowing for the world-first three-dimensional reconstruction of individual particles and vortex filament trajectories. Preliminary data, including the first three-dimensional observation of a vortex reconnection are presented.

New environmentally friendly MSPD solid support based on golden mussel shell: characterization and application for extraction of organic contaminants from mussel tissue.

PubMed

Rombaldi, Caroline; de Oliveira Arias, Jean Lucas; Hertzog, Gabriel Ianzer; Caldas, Sergiane Souza; Vieira, João P; Primel, Ednei Gilberto

2015-06-01

The use of golden mussel shells as a solid support in vortex-assisted matrix solid-phase dispersion (MSPD) was evaluated for the first time for extraction of residues of 11 pesticides and nine pharmaceutical and personal care products from mussel tissue samples. After they had been washed, dried, and milled, the mussel shells were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The MSPD procedure with analysis by liquid chromatography-tandem mass spectrometry allowed the determination of target analytes at trace concentrations (nanograms per gram), with mean recoveries ranging from 61 to 107 % and relative standard deviations lower than 18 %. The optimized method consisted of dispersion of 0.5 g of mussel tissue, 0.5 g of NaSO4, and 0.5 g of golden mussel shell for 5 min, and subsequent extraction with 5 mL of ethyl acetate. The matrix effect was evaluated, and a low effect was found for all compounds. The results showed that mussel shell is an effective material and a less expensive material than materials that have traditionally been used, i.e., it may be used in the MSPD dispersion step during the extraction of pesticides and pharmaceutical and personal care products from golden mussel tissues. Graphical Abstract Vortex-assited matrix solid-phase dispersion for extraction of 11 pesticides and 9 PPCPs care products from mussel tissue samples.

Sudden stratospheric warmings: statistical characteristics and influence on NO2 and O3 total contents

NASA Astrophysics Data System (ADS)

Ageyeva, V. Yu.; Gruzdev, A. N.; Elokhov, A. S.; Mokhov, I. I.; Zueva, N. E.

2017-09-01

Statistical characteristics of major and minor sudden stratospheric warmings (SSWs) in the Northern Hemisphere (NH) for 1958-2015 are analyzed using data of NCEP-NCAR, ERA 40, and ERA-Interim reanalyses. Dependencies of the number of major SSWs with the displacement of the circumpolar stratospheric vortex and the number of minor SSWs on the phase of the quasi-biennial oscillation (QBO) of the equatorial stratospheric wind and on the level of solar activity (SA) in the 11-year solar cycle have been revealed. Major SSWs accompanied by a displacement of the polar vortex occur more often at a high level of SA and at the easterly phase of the QBO in the 50-40 hPa layer, while minor SSWs occur more often at a low SA level and at the westerly phase of the QBO. An analysis of spatiotemporal dynamics of the stratospheric polar vortex at major SSWs is performed. The most probable directions of vortex displacement caused by SSWs have been revealed. Influences of the major SSWs on the total contents of NO2 and ozone, as well as on stratosphere temperature, are analyzed.

A Comparison of Shadowgraphy and X-ray Computed Tomography in Liquid Spray Analysis

DTIC Science & Technology

2014-11-14

atomizers and downstream of the nozzle exit gives insight into optimizing atomizers, particularly for combustion applications. The performance of gas ...regions near the spray nozzle [9, 10]. Because light refraction by liquid sheets is significant, these areas all cast a full shadow on the camera...hollow-cone pressure swirl design. Within this nozzle design, liquid swirls around an air-cored vortex. Upon exiting, the fluid expands due to its

MSFC Combustion Devices in 2001

NASA Technical Reports Server (NTRS)

Dexter, Carol; Turner, James (Technical Monitor)

2001-01-01

The objectives of the project detailed in this viewgraph presentation were to reduce thrust assembly weights to create lighter engines and to increase the cycle life and/or operating temperatures. Information is given on material options (metal matrix composites and polymer matrix composites), ceramic matrix composites subscale liners, lightweight linear chambers, lightweight injector development, liquid/liquid preburner tasks, and vortex chamber tasks.

Calculation of the wetting parameter from a cluster model in the framework of nanothermodynamics.

PubMed

García-Morales, V; Cervera, J; Pellicer, J

2003-06-01

The critical wetting parameter omega(c) determines the strength of interfacial fluctuations in critical wetting transitions. In this Brief Report, we calculate omega(c) from considerations on critical liquid clusters inside a vapor phase. The starting point is a cluster model developed by Hill and Chamberlin in the framework of nanothermodynamics [Proc. Natl. Acad. Sci. USA 95, 12779 (1998)]. Our calculations yield results for omega(c) between 0.52 and 1.00, depending on the degrees of freedom considered. The findings are in agreement with previous experimental results and give an idea of the universal dynamical behavior of the clusters when approaching criticality. We suggest that this behavior is a combination of translation and vortex rotational motion (omega(c)=0.84).

Frequency lock-in and phase synchronization of vortex shedding behind circular cylinder due to surface waves

NASA Astrophysics Data System (ADS)

Gunnoo, Hans; Abcha, Nizar; Ezersky, Alexander

2016-02-01

The influence of harmonic surface wave on non-regular Karman Vortex Street is investigated. In our experiments, Karman Street arises behind a vertical circular cylinder in a water flow and harmonic surface waves propagating upstream. It is found that surface waves can modify regimes of shedding in Karman Street: frequency lock-in and synchronization of vortex shedding can arise. Intensive surface waves can excite symmetric vortex street instead of chess-like street, and completely suppress shedding behind the cylinder. It is shown experimentally that such effects occur if frequency of harmonic surface wave is approximately twice higher than the frequency of vortex shedding. Region of frequency lock-in is found on the plane amplitude-frequency of surface wave.

Understanding dynamics of Martian winter polar vortex with “improved” moist-convective shallow water model

NASA Astrophysics Data System (ADS)

Rostami, M.; Zeitlin, V.

2017-12-01

We show how the properties of the Mars polar vortex can be understood in the framework of a simple shallow-water type model obtained by vertical averaging of the adiabatic “primitive” equations, and “improved” by inclusion of thermal relaxation and convective fluxes due to the phase transitions of CO 2, the major constituent of the Martian atmosphere. We perform stability analysis of the vortex, show that corresponding mean zonal flow is unstable, and simulate numerically non-linear saturation of the instability. We show in this way that, while non-linear adiabatic saturation of the instability tends to reorganize the vortex, the diabatic effects prevent this, and thus provide an explanation of the vortex form and longevity.

Generating multiple orbital angular momentum vortex beams using a metasurface in radio frequency domain

NASA Astrophysics Data System (ADS)

Yu, Shixing; Li, Long; Shi, Guangming; Zhu, Cheng; Shi, Yan

2016-06-01

In this paper, an electromagnetic metasurface is designed, fabricated, and experimentally demonstrated to generate multiple orbital angular momentum (OAM) vortex beams in radio frequency domain. Theoretical formula of compensated phase-shift distribution is deduced and used to design the metasurface to produce multiple vortex radio waves in different directions with different OAM modes. The prototype of a practical configuration of square-patch metasurface is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that multiple OAM vortex waves can be simultaneously generated by using a single electromagnetic metasurface. The proposed method paves an effective way to generate multiple OAM vortex waves in radio and microwave wireless communication applications.

Evaluation of Impinging Stream Vortex Chamber Concepts for Liquid Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Trinh, Huu P.; Bullard, Brad; Kopicz, Charles; Michaels, Scott

2002-01-01

To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for liquid rocket engine applications. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concepts not only offer system simplicity, but also enhance the combustion performance. Test results have shown that chamber performance is markedly high even at a low chamber length-to-diameter ratio (LD). This incentive can be translated to a convenience in the thrust chamber packaging. Variations of the vortex chamber concepts have been introduced in the past few decades. These investigations include an ongoing work at Orbital Technologies Corporation (ORBITEC). By injecting the oxidizer tangentially at the chamber convergence and fuel axially at the chamber head end, Knuth et al. were able to keep the wall relatively cold. A recent investigation of the low L/D vortex chamber concept for gel propellants was conducted by Michaels. He used both triplet (two oxidizer orifices and one fuel orifice) and unlike impinging schemes to inject propellants tangentially along the chamber wall. Michaels called the subject injection scheme an Impinging Stream Vortex Chamber (ISVC). His preliminary tests showed that high performance, with an Isp efficiency of 9295, can be obtained. MSFC and the U. S. Army are jointly investigating an application of the ISVC concept for the cryogenic oxygen/hydrocarbon propellant system. This vortex chamber concept is currently tested with gel propellants at AMCOM at Redstone Arsenal, Alabama. A version of this concept for the liquid oxygen (LOX) hydrocarbon fuel (RP-1) system has been derived from the one for the gel propellant. An unlike impinging injector was employed to deliver the propellants to the chamber. MSFC is also conducting an alternative injection scheme, called the chasing injector, associated with this vortex chamber concept. In this injection technique, both propellant jets and their impingement point are in the same chamber cross-sectional plane. Long duration tests (approximately up to 15 seconds) will be conducted on the ISVC to study the thermal effects. This paper will report the progress of the subject efforts at NASA Marshall Space Flight Center. Thrust chamber performance and thermal wall compatibility will be evaluated. The chamber pressures, wall temperatures, and thrust will be measured as appropriate. The test data will be used to validate CFD models, which, in turn, will be used to design the optimum vortex chambers. Measurements in the previous tests showed that the chamber pressures vary significantly with radius. This is due to the existence of the vortices in the chamber flow field. Hence, the combustion efficiency may not be easily determined from chamber pressure. For this project, measured thrust data will be collected. The performance comparison will be in terms of specific impulse efficiencies. In addition to the thrust measurements, several pressure and temperature readings at various locations on the chamber head faceplate and the chamber wall will be made. The first injector and chamber were designed and fabricated based on the available data and experience gained during gel propellant system tests by the U.S. Army. The alternate injector for the ISVC was also fabricated. Hot-fire tests of the vortex chamber are about to start and are expected to complete in February of 2003 at the TS115 facility of MSFC.

Generation of dark solitons and their instability dynamics in two-dimensional condensates

NASA Astrophysics Data System (ADS)

Verma, Gunjan; Rapol, Umakant D.; Nath, Rejish

2017-04-01

We analyze numerically the formation and the subsequent dynamics of two-dimensional matter wave dark solitons in a Thomas-Fermi rubidium condensate using various techniques. An initially imprinted sharp phase gradient leads to the dynamical formation of a stationary soliton as well as very shallow gray solitons, whereas a smooth gradient only creates gray solitons. The depth and hence, the velocity of the soliton is provided by the spatial width of the phase gradient, and it also strongly influences the snake-instability dynamics of the two-dimensional solitons. The vortex dipoles stemming from the unstable soliton exhibit rich dynamics. Notably, the annihilation of a vortex dipole via a transient dark lump or a vortexonium state, the exchange of vortices between either a pair of vortex dipoles or a vortex dipole and a single vortex, and so on. For sufficiently large width of the initial phase gradient, the solitons may decay directly into vortexoniums instead of vortex pairs, and also the decay rate is augmented. Later, we discuss alternative techniques to generate dark solitons, which involve a Gaussian potential barrier and time-dependent interactions, both linear and periodic. The properties of the solitons can be controlled by tuning the amplitude or the width of the potential barrier. In the linear case, the number of solitons and their depths are determined by the quench time of the interactions. For the periodic modulation, a transient soliton lattice emerges with its periodicity depending on the modulation frequency, through a wave number selection governed by the local Bogoliubov spectrum. Interestingly, for sufficiently low barrier potential, both Faraday pattern and soliton lattice coexist. The snake instability dynamics of the soliton lattice is characteristically modified if the Faraday pattern is present.

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes.

PubMed

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-11

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

NASA Astrophysics Data System (ADS)

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-01

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

Vortex dynamics of in-line twin synthetic jets in a laminar boundary layer

NASA Astrophysics Data System (ADS)

Wen, Xin; Tang, Hui; Duan, Fei

2015-08-01

An experimental investigation is conducted on the vortices induced by twin synthetic jets (SJs) in line with a laminar boundary layer flow over a flat plate. The twin SJs operating at four different phase differences, i.e., Δϕ = 0°, 90°, 180°, and 270°, are visualized using a stereoscopic color dye visualization system and measured using a two-dimensional particle image velocimetry (PIV) system. It is found that depending on the phase difference of twin SJs, three types of vortex structures are produced. At Δϕ = 90°, the two hairpin vortices interact in a very constructive way in terms of the vortex size, strength, and celerity, forming one combined vortex. At Δϕ = 270°, the two individual hairpin vortices do not have much interaction, forming two completely separated hairpin vortices that behave like doubling the frequency of the single SJ case. At Δϕ = 0° and 180°, the two hairpin vortices produced by the twin SJ actuators are close enough, with the head of one hairpin vortex coupled with the legs of the other, forming partially interacting vortex structures. Quantitative analysis of the twin SJs is conducted, including the time histories of vortex circulation in the mid-span plane as well as a selected spanwise-wall-normal plane, and the influence of the twin SJs on the boundary layer flow filed. In addition, dynamic mode decomposition analysis of the PIV data is conducted to extract representative coherent structures. Through this study, a better understanding in the vortex dynamics associated with the interaction of in-line twin SJs in laminar boundary layers is achieved, which provides useful information for future SJ-array applications.

Interaction of a trailing vortex with an oscillating wing

NASA Astrophysics Data System (ADS)

McKenna, C.; Fishman, G.; Rockwell, D.

2018-01-01

A technique of particle image velocimetry is employed to characterize the flow structure of a trailing vortex incident upon the tip region of an oscillating wing (plate). The amplitude and velocity of the wing are nearly two orders of magnitude smaller than the wing chord and free stream velocity, respectively. Depending upon the outboard displacement of the incident vortex relative to the wing tip, distinctive patterns of upwash, downwash, and shed vorticity are observed. These patterns are a strong function of the phase of the wing motion during its oscillation cycle. At a given phase, the wing oscillation induces upwash that is reinforced by the upwash of the incident vortex, giving a maximum net upwash. Conversely, when these two origins of upwash counteract, rather than reinforce, one another during the oscillation cycle, the net upwash attains minimum value. Analogous interpretations hold for regions of maximum and minimum net downwash located outboard of the regions of upwash. The magnitude and scale of the vorticity shed from the tip of the wing are directly correlated with the net upwash, which takes different forms related to the outboard displacement of the incident vortex. As the location of the incident vortex is displaced towards the wing tip, both the maximum upwash and the maximum vorticity of the tip vortex initially increase and then decrease. For the limiting case where the incident vortex impinges directly upon the tip of the wing, there is no tip vortex or induced region of upwash. Furthermore, at small values of vortex displacement from the wing tip, the position of the incident vortex varies significantly from its nominal position during the oscillation cycle. All of the foregoing features are interpreted in conjunction with the flow topology in the form of streamlines and critical points, superposed on patterns of vorticity. It is shown that despite the small amplitude of the wing motion, the flow topology is fundamentally different at maximum positive and negative values of the velocity of the wing tip, that is, they are not symmetric.

Magnetic vortex nucleation modes in static magnetic fields

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

Vanatka, Marek; Urbanek, Michal; Jira, Roman

The magnetic vortex nucleation process in nanometer- and micrometer-sized magnetic disks undergoes several phases with distinct spin configurations called the nucleation states. Before formation of the final vortex state, small submicron disks typically proceed through the so-called C-state while the larger micron-sized disks proceed through the more complicated vortex-pair state or the buckling state. This work classifies the nucleation states using micromagnetic simulations and provides evidence for the stability of vortex-pair and buckling states in static magnetic fields using magnetic imaging techniques and electrical transport measurements. Lorentz Transmission Electron Microscopy and Magnetic Transmission X-ray Microscopy are employed to reveal themore » details of spin configuration in each of the nucleation states. We further show that it is possible to unambiguously identify these states by electrical measurements via the anisotropic magnetoresistance effect. Combination of the electrical transport and magnetic imaging techniques confirms stability of a vortex-antivortex-vortex spin configuration which emerges from the buckling state in static magnetic fields.« less

Magnetic vortex nucleation modes in static magnetic fields

DOE PAGES

Vanatka, Marek; Urbanek, Michal; Jira, Roman; ...

2017-10-03

The magnetic vortex nucleation process in nanometer- and micrometer-sized magnetic disks undergoes several phases with distinct spin configurations called the nucleation states. Before formation of the final vortex state, small submicron disks typically proceed through the so-called C-state while the larger micron-sized disks proceed through the more complicated vortex-pair state or the buckling state. This work classifies the nucleation states using micromagnetic simulations and provides evidence for the stability of vortex-pair and buckling states in static magnetic fields using magnetic imaging techniques and electrical transport measurements. Lorentz Transmission Electron Microscopy and Magnetic Transmission X-ray Microscopy are employed to reveal themore » details of spin configuration in each of the nucleation states. We further show that it is possible to unambiguously identify these states by electrical measurements via the anisotropic magnetoresistance effect. Combination of the electrical transport and magnetic imaging techniques confirms stability of a vortex-antivortex-vortex spin configuration which emerges from the buckling state in static magnetic fields.« less

Quasiclassical analysis of vortex lattice states in Rashba noncentrosymmetric superconductors

NASA Astrophysics Data System (ADS)

Dan, Yuichiro; Ikeda, Ryusuke

2015-10-01

Vortex lattice states occurring in noncentrosymmetric superconductors with a spin-orbit coupling of Rashba type under a magnetic field parallel to the symmetry plane are examined by assuming the s -wave pairing case and in an approach combining the quasiclassical theory with the Landau level expansion of the superconducting order parameter. The resulting field-temperature phase diagrams include not only a discontinuous transition but a continuous crossover between different vortex lattice structures, and, further, a critical end point of a structural transition line is found at an intermediate field and a low temperature in the present approach. It is pointed out that the strange field dependence of the vortex lattice structure is a consequence of that of its anisotropy stemming from the Rashba spin-orbit coupling, and that the critical end point is related to the helical phase modulation peculiar to these materials in the ideal Pauli-limited case. Furthermore, calculation results on the local density of states detectable in STM experiments are also presented.

Commissioning and first light results of an L'-band vortex coronagraph with the Keck II adaptive optics NIRC2 science instrument

NASA Astrophysics Data System (ADS)

Femenía Castellá, Bruno; Serabyn, Eugene; Mawet, Dimitri; Absil, Olivier; Wizinowich, Peter; Matthews, Keith; Huby, Elsa; Bottom, Michael; Campbell, Randy; Chan, Dwight; Carlomagno, Brunella; Cetre, Sylvain; Defrère, Denis; Delacroix, Christian; Gomez Gonzalez, Carlos; Jolivet, Aïssa; Karlsson, Mikael; Lanclos, Kyle; Lilley, Scott; Milner, Steven; Ngo, Henry; Reggiani, Maddalena; Simmons, Julia; Tran, Hien; Vargas Catalan, Ernesto; Wertz, Olivier

2016-07-01

On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph operates in the L' band not only in order to take advantage from the favorable star/planet contrast ratio when observing beyond the K band, but also to exploit the fact that the Keck II Adaptive Optics (AO) system delivers nearly extreme adaptive optics image quality (Strehl ratios values near 90%) at 3.7μm. We describe the hardware installation of the vortex phase mask during a routine NIRC2 service mission. The success of the project depends on extensive software development which has allowed the achievement of exquisite real-time pointing control as well as further contrast improvements by using speckle nulling to mitigate the effect of static speckles. First light of the new coronagraphic mode was on June 2015 with already very good initial results. Subsequent commissioning nights were interlaced with science nights by members of the VORTEX team with their respective scientific programs. The new capability and excellent results so far have motivated the VORTEX team and the Keck Science Steering Committee (KSSC) to offer the new mode in shared risk mode for 2016B.

Competing forces in liquid metal electrodes and batteries

NASA Astrophysics Data System (ADS)

Ashour, Rakan F.; Kelley, Douglas H.; Salas, Alejandro; Starace, Marco; Weber, Norbert; Weier, Tom

2018-02-01

Liquid metal batteries are proposed for low-cost grid scale energy storage. During their operation, solid intermetallic phases often form in the cathode and are known to limit the capacity of the cell. Fluid flow in the liquid electrodes can enhance mass transfer and reduce the formation of localized intermetallics, and fluid flow can be promoted by careful choice of the locations and topology of a battery's electrical connections. In this context we study four phenomena that drive flow: Rayleigh-Bénard convection, internally heated convection, electro-vortex flow, and swirl flow, in both experiment and simulation. In experiments, we use ultrasound Doppler velocimetry (UDV) to measure the flow in a eutectic PbBi electrode at 160 °C and subject to all four phenomena. In numerical simulations, we isolate the phenomena and simulate each separately using OpenFOAM. Comparing simulated velocities to experiments via a UDV beam model, we find that all four phenomena can enhance mass transfer in LMBs. We explain the flow direction, describe how the phenomena interact, and propose dimensionless numbers for estimating their mutual relevance. A brief discussion of electrical connections summarizes the engineering implications of our work.

Atomization of a High Speed Jet

NASA Astrophysics Data System (ADS)

Xu, Zhiliang; Samulyak, Roman; Li, Xiaolin; Tzanos, Constantine

2005-11-01

We present a numerical study of the jet breakup and spray formation in a diesel engine by the Front Tracking method. The mechanisms of jet breakup and spray formation of a high speed diesel jet injected through a circular nozzle are the key to design a fuel efficient, nonpolluting diesel engine. Many parameters such as the nuzzle shape, the velocity and the turbulence of the jet and the thermodynamic states of liquid and gas could be contributing causes for jet breakup. We conduct the simulations for the jet breakup within a 2D axis-symmetric geometry. Our goal is to model the spray at a micro-physical level, with the creation of individual droplets. The problem is multiscale. The droplets are a few microns in size. The nozzle is about 0.2 mm in diameter and 1 mm in length. In order to resolve various physical patterns such as vortex, shock waves, vacuum and track droplets and spray, the Burger-Colella adaptive mesh refinement technique is used. We model mixed vapor-liquid region through a heterogeneous model with dynamic vapor bubble insertion. On the liquid/vapor interface, a phase transition problem is solved numerically.

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

Radzihovsky, Leo

Motivated by a realization of imbalanced Feshbach-resonant atomic Fermi gases, we formulate a low-energy theory of the Fulde-Ferrell and the Larkin-Ovchinnikov (LO) states and use it to analyze fluctuations, stability, and phase transitions in these enigmatic finite momentum-paired superfluids. Focusing on the unidirectional LO pair-density-wave state, which spontaneously breaks the continuous rotational and translational symmetries, we show that it is characterized by two Goldstone modes, corresponding to a superfluid phase and a smectic phonon. Because of the liquid-crystalline ''softness'' of the latter, at finite temperature the three-dimensional state is characterized by a vanishing LO order parameter, quasi-Bragg peaks in themore » structure and momentum distribution functions, and a ''charge''-4, paired-Cooper-pairs, off-diagonal long-range order, with a superfluid-stiffness anisotropy that diverges near a transition into a nonsuperfluid state. In addition to conventional integer vortices and dislocations, the LO superfluid smectic exhibits composite half-integer vortex-dislocation defects. A proliferation of defects leads to a rich variety of descendant states, such as the charge-4 superfluid and Fermi-liquid nematics and topologically ordered nonsuperfluid states, that generically intervene between the LO state and the conventional superfluid and the polarized Fermi liquid at low and high imbalance, respectively. The fermionic sector of the LO gapless superconductor is also quite unique, exhibiting a Fermi surface of Bogoliubov quasiparticles associated with the Andreev band of states, localized on the array of the LO domain walls.« less

Post-coronagraphic tip-tilt sensing for vortex phase masks: The QACITS technique

NASA Astrophysics Data System (ADS)

Huby, E.; Baudoz, P.; Mawet, D.; Absil, O.

2015-12-01

Context. Small inner working angle coronagraphs, such as the vortex phase mask, are essential to exploit the full potential of ground-based telescopes in the context of exoplanet detection and characterization. However, the drawback of this attractive feature is a high sensitivity to pointing errors, which degrades the performance of the coronagraph. Aims: We propose a tip-tilt retrieval technique based on the analysis of the final coronagraphic image, hereafter called Quadrant Analysis of Coronagraphic Images for Tip-tilt Sensing (QACITS). Methods: Under the assumption of small phase aberrations, we show that the behavior of the vortex phase mask can be simply described from the entrance pupil to the Lyot stop plane with Zernike polynomials. This convenient formalism is used to establish the theoretical basis of the QACITS technique. We performed simulations to demonstrate the validity and limits of the technique, including the case of a centrally obstructed pupil. Results: The QACITS technique principle is validated with experimental results in the case of an unobstructed circular aperture, as well as simulations in presence of a central obstruction. The typical configuration of the Keck telescope (24% central obstruction) has been simulated with additional high order aberrations. In these conditions, our simulations show that the QACITS technique is still adapted to centrally obstructed pupils and performs tip-tilt retrieval with a precision of 5 × 10-2λ/D when wavefront errors amount to λ/ 14 rms and 10-2λ/D for λ/ 70 rms errors (with λ the wavelength and D the pupil diameter). Conclusions: We have developed and demonstrated a tip-tilt sensing technique for vortex coronagraphs. The implementation of the QACITS technique is based on the analysis of the scientific image and does not require any modification of the original setup. Current facilities equipped with a vortex phase mask can thus directly benefit from this technique to improve the contrast performance close to the axis.

Coarsening dynamics of binary liquids with active rotation.

PubMed

Sabrina, Syeda; Spellings, Matthew; Glotzer, Sharon C; Bishop, Kyle J M

2015-11-21

Active matter comprised of many self-driven units can exhibit emergent collective behaviors such as pattern formation and phase separation in both biological (e.g., mussel beds) and synthetic (e.g., colloidal swimmers) systems. While these behaviors are increasingly well understood for ensembles of linearly self-propelled "particles", less is known about the collective behaviors of active rotating particles where energy input at the particle level gives rise to rotational particle motion. A recent simulation study revealed that active rotation can induce phase separation in mixtures of counter-rotating particles in 2D. In contrast to that of linearly self-propelled particles, the phase separation of counter-rotating fluids is accompanied by steady convective flows that originate at the fluid-fluid interface. Here, we investigate the influence of these flows on the coarsening dynamics of actively rotating binary liquids using a phenomenological, hydrodynamic model that combines a Cahn-Hilliard equation for the fluid composition with a Navier-Stokes equation for the fluid velocity. The effect of active rotation is introduced though an additional force within the Navier-Stokes equations that arises due to gradients in the concentrations of clockwise and counter-clockwise rotating particles. Depending on the strength of active rotation and that of frictional interactions with the stationary surroundings, we observe and explain new dynamical behaviors such as "active coarsening" via self-generated flows as well as the emergence of self-propelled "vortex doublets". We confirm that many of the qualitative behaviors identified by the continuum model can also be found in discrete, particle-based simulations of actively rotating liquids. Our results highlight further opportunities for achieving complex dissipative structures in active materials subject to distributed actuation.

Phase-resolved and time-averaged puff motions of an excited stack-issued transverse jet

NASA Astrophysics Data System (ADS)

Hsu, C. M.; Huang, R. F.

2013-07-01

The dynamics of puff motions in an excited stack-issued transverse jet were studied experimentally in a wind tunnel. The temporal and spatial evolution processes of the puffs induced by acoustic excitation were examined using the smoke flow visualization method and high-speed particle image velocimetry. The temporal and spatial evolutions of the puffs were examined using phase-resolved ensemble-averaged velocity fields and the velocity, length scales, and vorticity characteristics of the puffs were studied. The time-averaged velocity fields were calculated to analyze the velocity distributions and vorticity contours. The results show that a puff consists of a pair of counter-rotating vortex rings. An initial vortex ring was formed due to a concentration of vorticity at the lee side of the issuing jet at the instant of the mid-oscillation cycle. A vortex ring rotating in the opposite direction to that of the initial vortex ring was subsequently formed at the upwind side of the issuing jet. These two counter-rotating vortex rings formed a "mushroom" vortex pair, which was deflected by the crossflow and traveled downstream along a time-averaged trajectory of zero vorticity. The trajectory was situated far above the time-averaged streamline evolving from the leading edge of the tube. The velocity magnitudes of the vortex rings at the upwind and the lee side decreased with time evolution as the puffs traveled downstream due to momentum dissipation and entrainment effects. The puffs traveling along the trajectory of zero vorticity caused large velocities to appear above the leading-edge streamline.

Modulation of the Polar Vortex by Energetic Particle Precipitation and Quasi-Biennial Oscillation via Ozone Loss

NASA Astrophysics Data System (ADS)

Asikainen, T.; Salminen, A.; Maliniemi, V.; Mursula, K.

2017-12-01

Energetic particle precipitation (EPP) has been shown to cause ozone loss in the stratosphere during polar winter. This has been suggested to enhance polar vortex with the effect propagating even to ground level, where it is observed as a more positive phase of the Northern Annular Mode (NAM), the dominant ground circulation pattern in the winter time at high latitudes. Recent research has also shown that the quasi-biennial oscillation (QBO) modulates the relationship between the ground NAM and EPP so that the positive correlation between the two is more clearly seen in the easterly phase of QBO measured at 30 hPa height especially during the late winter season. Here we elaborate the QBO modulated connection between EPP and NAM by studying how the EPP affects the stratospheric polar vortex in the two phases of the QBO. Since the EPP presumably affects the polar stratosphere via indirect ozone loss we will study how the EPP modulates the amount of ozone, the stratospheric temperatures and zonal winds in the two QBO phases.

Modulation of the polar vortex by energetic particle precipitation and Quasi-Biennial Oscillation via ozone loss

NASA Astrophysics Data System (ADS)

Salminen, Antti; Asikainen, Timo; Maliniemi, Ville; Mursula, Kalevi

2017-04-01

Energetic particle precipitation (EPP) has been shown to cause ozone loss in the stratosphere during polar winter. This has been suggested to enhance polar vortex with the effect propagating even to ground level, where it is observed as a more positive phase of the Northern Annular Mode (NAM), the dominant ground circulation pattern in the winter time at high latitudes. Recent research has also shown that the quasi-biennial oscillation (QBO) modulates the relationship between the ground NAM and EPP so that the positive correlation between the two is more clearly seen in the easterly phase of QBO measured at 30 hPa height especially during the late winter season. Here we elaborate the QBO modulated connection between EPP and NAM by studying how the EPP affects the stratospheric polar vortex in the two phases of the QBO. Since the EPP presumably affects the polar stratosphere via indirect ozone loss we will study how the EPP modulates the amount of ozone, the stratospheric temperatures and zonal winds in the two QBO phases.

Generating multiple orbital angular momentum vortex beams using a metasurface in radio frequency domain

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

Yu, Shixing; Li, Long, E-mail: lilong@mail.xidian.edu.cn, E-mail: gmshi@xidian.edu.cn; Shi, Guangming, E-mail: lilong@mail.xidian.edu.cn, E-mail: gmshi@xidian.edu.cn

In this paper, an electromagnetic metasurface is designed, fabricated, and experimentally demonstrated to generate multiple orbital angular momentum (OAM) vortex beams in radio frequency domain. Theoretical formula of compensated phase-shift distribution is deduced and used to design the metasurface to produce multiple vortex radio waves in different directions with different OAM modes. The prototype of a practical configuration of square-patch metasurface is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that multiple OAM vortex waves can be simultaneously generated by using a single electromagnetic metasurface. The proposed method paves an effectivemore » way to generate multiple OAM vortex waves in radio and microwave wireless communication applications.« less

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture

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

Taira, Yoshitaka; Zhang, Shukui

Here, diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture.

PubMed

Taira, Yoshitaka; Zhang, Shukui

2017-04-01

Diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this Letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture

DOE PAGES

Taira, Yoshitaka; Zhang, Shukui

2017-03-29

Here, diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Micromagnetic study of equilibrium states in nano hemispheroidal shells

NASA Astrophysics Data System (ADS)

Schultz, Keren; Schultz, Moty

2017-11-01

We present results of micromagnetic simulations of thin ferromagnetic nano hemispheroidal shells with sizes ranging from 5 to 50 nm (inside dimensions). Depending on the geometrical and magnetic parameters of the hemispheroidal shell, there exist three different magnetic phases: easy axis, onion and vortex. The profile for the vortex magnetization distribution is analyzed and the limitations and applicability of different vortex ansatzes are discussed. In addition, we investigate the total energy density for each of the magnetic distributions as a function of the hemispheroidal shell dimensions.

Quasi-Porous Plug With Vortex Chamber

NASA Technical Reports Server (NTRS)

Walsh, J. V.

1985-01-01

Pressure-letdown valve combines quasi-porous-plug and vortex-chamber in one controllable unit. Valve useful in fossil-energy plants for reducing pressures in such erosive two-phase process streams as steam/water, coal slurries, or combustion gases with entrained particles. Quasi-Porous Plug consists of plenums separated by perforated plates. Number or size of perforations increases with each succeeding stage to compensate for expansion. In Vortex Chamber, control flow varies to control swirl and therefore difference between inlet and outlet pressures.

Interaction of in-phase and out-of-phase flexible filament in fish schooling

NASA Astrophysics Data System (ADS)

Ud Din, Emad; Sung, Hyung

2011-11-01

Fish schooling is not merely a social behavior; schooling improves the efficiency of movement within the fluid environment. Inspired by the schooling from a hydrodynamic perspective, a group of aquatic animals is modeled as a collection of individuals arranged in a combination of tandem and side-by-side (diamond) formation. The downstream bodies are strongly influenced by the vortices shed by the upstream body shown by vortex-vortex and vortex-body interactions. Trailing fish takes advantage of this flow pattern for energy economy. To investigate the interactions between flexible bodies and vortices, in the present study three flexible flags in viscous flow are solved by numerical simulation using an improved version of the immersed boundary method for in-phase and out-of-phase filaments. The drag coefficient of the downstream filaments drops even below the value of a single flag. Such drag variations are influenced by the interactions between vortices shed by the upstream flexible body and vortices surrounding the downstream filaments. Interaction of the flexible flags is investigated as a function of the gap distance between flags and different bending coefficients, for in-phase and out-of-phase cases at intermediate Reynolds numbers. This study was supported by the Creative Research Initiatives of NRF/MEST (No. 2011-0000423) of Korea.

Wake Vortex Detection: Phased Microphone vs. Linear Infrasonic Array

NASA Technical Reports Server (NTRS)

Shams, Qamar A.; Zuckerwar, Allan J.; Sullivan, Nicholas T.; Knight, Howard K.

2014-01-01

Sensor technologies can make a significant impact on the detection of aircraft-generated vortices in an air space of interest, typically in the approach or departure corridor. Current state-of-the art sensor technologies do not provide three-dimensional measurements needed for an operational system or even for wake vortex modeling to advance the understanding of vortex behavior. Most wake vortex sensor systems used today have been developed only for research applications and lack the reliability needed for continuous operation. The main challenges for the development of an operational sensor system are reliability, all-weather operation, and spatial coverage. Such a sensor has been sought for a period of last forty years. Acoustic sensors were first proposed and tested by National Oceanic and Atmospheric Administration (NOAA) early in 1970s for tracking wake vortices but these acoustic sensors suffered from high levels of ambient noise. Over a period of the last fifteen years, there has been renewed interest in studying noise generated by aircraft wake vortices, both numerically and experimentally. The German Aerospace Center (DLR) was the first to propose the application of a phased microphone array for the investigation of the noise sources of wake vortices. The concept was first demonstrated at Berlins Airport Schoenefeld in 2000. A second test was conducted in Tarbes, France, in 2002, where phased microphone arrays were applied to study the wake vortex noise of an Airbus 340. Similarly, microphone phased arrays and other opto-acoustic microphones were evaluated in a field test at the Denver International Airport in 2003. For the Tarbes and Denver tests, the wake trajectories of phased microphone arrays and lidar were compared as these were installed side by side. Due to a built-in pressure equalization vent these microphones were not suitable for capturing acoustic noise below 20 Hz. Our group at NASA Langley Research Center developed and installed an infrasonic array at the Newport News-Williamsburg International Airport early in the year 2013. A pattern of pressure burst, high-coherence intervals, and diminishing-coherence intervals was observed for all takeoff and landing events without exception. The results of a phased microphone vs. linear infrasonic array comparison will be presented.

NEUTRONIC REACTOR OPERATIONAL METHOD AND CORE SYSTEM

DOEpatents

Winters, C.E.; Graham, C.B.; Culver, J.S.; Wilson, R.H.

1960-07-19

Homogeneous neutronic reactor systems are described wherein an aqueous fuel solution is continuously circulated through a spherical core tank. The pumped fuel solution-is injected tangentially into the hollow spherical interior, thereby maintaining vigorous rotation of the solution within the tank in the form of a vortex; gaseous radiolytic decomposition products concentrate within the axial vortex cavity. The evolved gas is continuously discharged through a gas- outlet port registering with an extremity of the vortex cavity. and the solution stream is discharged through an annular liquid outlet port concentrically encircling the gas outlet by virtue of which the vortex and its cavity are maintained precisely axially aligned with the gas outlet. A primary heat exchanger extracts useful heat from the hot effluent fuel solution before its recirculation into the core tank. Hollow cylinders and other alternative core- tank configurations defining geometric volumes of revolution about a principal axis are also covered. AEC's Homogeneous Reactor Experiment No. 1 is a preferred embodiment.

Rapid determination of 9 aromatic amines in mainstream cigarette smoke by modified dispersive liquid liquid microextraction and ultraperformance convergence chromatography tandem mass spectrometry.

PubMed

Deng, Huimin; Yang, Fei; Li, Zhonghao; Bian, Zhaoyang; Fan, Ziyan; Wang, Ying; Liu, Shanshan; Tang, Gangling

2017-07-21

Aromatic amines in mainstream cigarette smoke have long been monitored due to their carcinogenic toxicity. In this work, a reliable and rapid method was developed for the simultaneous determination of 9 aromatic amines in mainstream cigarette smoke by modified dispersive liquid liquid microextraction (DLLME) and ultraperformance convergence chromatography tandem mass spectrometry (UPC 2 -MS/MS). Briefly, the particulate phase of the cigarette smoke was captured by a Cambridge filter pad, and diluted hydrogen chloride aqueous solution is employed to extract the aromatic amines under mechanical shaking. After alkalization with sodium hydroxide solution, small amount of toluene was introduced to further extract and enrich aromatic amines by modified DLLME under vortexing. After centrifugation, toluene phase was purified by a universal QuEChERS cleanup kit and was finally analyzed by UPC 2 -MS/MS. Attributing to the superior performance of UPC 2 -MS/MS, this novel approach allowed the separation and determination of 9 aromatic amines within 5.0min with satisfactory resolution and sensitivity. The proposed method was finally validated using Kentucky reference cigarette 3R4F, and emission levels of targeted aromatic amines determined were comparable to previously reported methods At three different spiked levels, the recoveries of most analytes were ranged from 74.01% to 120.50% with relative standard deviation (RSD) less than 12%, except that the recovery of p-toluidine at low spiked level and 3-aminobiphenyl at medium spiked level was 62.77% and 69.37% respectively. Thus, this work provides a novel alternative method for the simultaneous analysis of 9 aromatic amines in mainstream cigarette smoke. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetohydrodynamic effects in liquid metal batteries

NASA Astrophysics Data System (ADS)

Stefani, F.; Galindo, V.; Kasprzyk, C.; Landgraf, S.; Seilmayer, M.; Starace, M.; Weber, N.; Weier, T.

2016-07-01

Liquid metal batteries (LMBs) consist of two liquid metal electrodes and a molten salt ionic conductor sandwiched between them. The density ratios allow for a stable stratification of the three layers. LMBs were already considered as part of energy conversion systems in the 1960s and have recently received renewed interest for economical large-scale energy storage. In this paper, we concentrate on the magnetohydrodynamic aspects of this cell type with special focus on electro-vortex flows and possible effects of the Tayler instability.

Formation of vortex wakes at flow separation from plate

NASA Astrophysics Data System (ADS)

Gorelov, D. N.; Govorova, A. I.

2017-05-01

The plane nonlinear initial boundary value problem about the separated flow past a plate set in motion at a constant velocity from the state of rest has been considered. Results of a numerical experiment which have allowed us to trace in detail the vortex-wake formation process behind a vertical plate are reported. It is shown that, after the beginning of the plate motion, several stable vortical structures, including a Karman street, form in succession behind the plate. It is found that, on the emergence of the Karman street, there occurs a sharp and substantial growth of vortex-wake intensity and hydrodynamic drag force with a pulsating time behavior. A conclusion about the origination, in this regime, of self-sustained oscillations of the liquid in the vicinity of the plate is drawn.

Crossflow Stability and Transition Experiments in Swept-Wing Flow

NASA Technical Reports Server (NTRS)

Dagenhart, J. Ray; Saric, William S.

1999-01-01

An experimental examination of crossflow instability and transition on a 45deg swept wing was conducted in the Arizona State University Unsteady Wind Tunnel. The stationary-vortex pattern and transition location are visualized by using both sublimating chemical and liquid-crystal coatings. Extensive hot-wire measurements were obtained at several measurement stations across a single vortex track. The mean and travelling wave disturbances were measured simultaneously. Stationary crossflow disturbance profiles were determined by subtracting either a reference or a span-averaged velocity profile from the mean velocity data. Mean, stationary crossflow, and traveling wave velocity data were presented as local boundary layer profiles and contour plots across a single stationary crossflow vortex track. Disturbance mode profiles and growth rates were determined. The experimental data are compared with predictions from linear stability theory.

Duality-mediated critical amplitude ratios for the (2 + 1)-dimensional S = 1XY model

NASA Astrophysics Data System (ADS)

Nishiyama, Yoshihiro

2017-09-01

The phase transition for the (2 + 1)-dimensional spin-S = 1XY model was investigated numerically. Because of the boson-vortex duality, the spin stiffness ρs in the ordered phase and the vortex-condensate stiffness ρv in the disordered phase should have a close relationship. We employed the exact diagonalization method, which yields the excitation gap directly. As a result, we estimate the amplitude ratios ρs,v/Δ (Δ: Mott insulator gap) by means of the scaling analyses for the finite-size cluster with N ≤ 22 spins. The ratio ρs/ρv admits a quantitative measure of deviation from selfduality.

QBO Influence on Polar Stratospheric Variability in the GEOS Chemistry-Climate Model

NASA Technical Reports Server (NTRS)

Hurwitz, M. M.; Oman, L. D.; Li, F.; Slong, I.-S.; Newman, P. A.; Nielsen, J. E.

2010-01-01

The quasi-biennial oscillation modulates the strength of both the Arctic and Antarctic stratospheric vortices. Model and observational studies have found that the phase and characteristics of the quasi-biennial oscillation (QBO) contribute to the high degree of variability in the Arctic stratosphere in winter. While the Antarctic stratosphere is less variable, recent work has shown that Southern Hemisphere planetary wave driving increases in response to "warm pool" El Nino events that are coincident with the easterly phase of the QBO. These events hasten the breakup of the Antarctic polar vortex. The Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) is now capable of generating a realistic QBO, due a new parameterization of gravity wave drag. In this presentation, we will use this new model capability to assess the influence of the QBO on polar stratospheric variability. Using simulations of the recent past, we will compare the modeled relationship between QBO phase and mid-winter vortex strength with the observed Holton-Tan relation, in both hemispheres. We will use simulations of the 21 St century to estimate future trends in the relationship between QBO phase and vortex strength. In addition, we will evaluate the combined influence of the QBO and El Nino/Southern Oscillation (ENSO) on the timing of the breakup of the polar stratospheric vortices in the GEOS CCM. We will compare the influence of these two natural phenomena with trends in the vortex breakup associated with ozone recovery and increasing greenhouse gas concentrations.

Post-stenotic plug-like jet with a vortex ring demonstrated by 4D flow MRI.

PubMed

Kim, Guk Bae; Ha, Hojin; Kweon, Jihoon; Lee, Sang Joon; Kim, Young-Hak; Yang, Dong Hyun; Kim, Namkug

2016-05-01

To investigate the details of the flow structure of a plug-like jet that had a vortex ring in pulsatile stenotic phantoms using 4D flow MRI. Pulsatile Newtonian flows in two stenotic phantoms with 50% and 75% reductions in area were scanned by 4D flow MRI. Blood analog working fluid was circulated via the stenotic phantom using a pulsatile pump at a constant pulsating frequency of 1Hz. The velocity and vorticity fields of the plug-like jet with a vortex ring were quantitatively analyzed in the spatial and temporal domains. Pulsatile stenotic flow showed a plug-like jet at the specific stenotic degree of 50% in our pulsatile waveform design. This plug-like jet was found at the decelerating period in the post-stenotic region of 26.4mm (1.2 D). It revealed a vortex ring structure with vorticity strength in the range of ±100s(-1). We observed a plug-like jet with a vortex ring in pulsatile stenotic flow by in vitro visualization using 4D flow MRI. In this plug-like jet, the local fastest flow region occurred at the post-systole phase in the post-stenotic region, which was distinguishable from a typical stenotic jet flow at systole phase. Copyright © 2015 Elsevier Inc. All rights reserved.

Comparison of the mechanical properties of rotary instruments made of conventional nickel-titanium wire, M-wire, or nickel-titanium alloy in R-phase.

PubMed

Lopes, Hélio P; Gambarra-Soares, Thaiane; Elias, Carlos N; Siqueira, José F; Inojosa, Inês F J; Lopes, Weber S P; Vieira, Victor T L

2013-04-01

This study compared the mechanical properties of endodontic instruments made of conventional nickel-titanium (NiTi) wire (K(3) and Revo-S SU), M-Wire (ProFile Vortex), or NiTi alloy in R-phase (K(3)XF). The test instruments were subjected to mechanical tests to evaluate resistance to bending (flexibility), cyclic fatigue, and torsional load in clockwise rotation. Data were statistically evaluated by the analysis of variance test and the Student-Newman-Keuls test for multiple comparisons. In the bending resistance test, flexibility decreased in the following order: K(3)XF > Revo-S SU > ProFile Vortex > K(3). The ranking in the fatigue resistance test was the following: K(3)XF > K(3) > ProFile Vortex > Revo-S SU. In the torsional assay, the angular deflection at failure decreased in the following order: K(3)XF > Revo-S SU > K(3) > ProFile Vortex. For the maximum torque values, the ranking was K(3) > K(3)XF > ProFile Vortex > Revo-S SU. The results showed that the K(3)XF instrument, which is made of NiTi alloy in R-phase, had the overall best performance in terms of flexibility, angular deflection at failure, and cyclic fatigue resistance. In addition to the alloy from which the instrument is manufactured, the design and dimensions are important determinants of the mechanical performance of endodontic instruments. Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

A planar chiral meta-surface for optical vortex generation and focusing

PubMed Central

Ma, Xiaoliang; Pu, Mingbo; Li, Xiong; Huang, Cheng; Wang, Yanqin; Pan, Wenbo; Zhao, Bo; Cui, Jianhua; Wang, Changtao; Zhao, ZeYu; Luo, Xiangang

2015-01-01

Data capacity is rapidly reaching its limit in modern optical communications. Optical vortex has been explored to enhance the data capacity for its extra degree of freedom of angular momentum. In traditional means, optical vortices are generated using space light modulators or spiral phase plates, which would sharply decrease the integration of optical communication systems. Here we experimentally demonstrate a planar chiral antenna array to produce optical vortex from a circularly polarized light. Furthermore, the antenna array has the ability to focus the incident light into point, which greatly increases the power intensity of the generated optical vortex. This chiral antenna array may have potential application in highly integrated optical communication systems. PMID:25988213

Kinematics of the Doped Quantum Vortices in Superfluid Helium Droplets

NASA Astrophysics Data System (ADS)

Bernando, Charles; Vilesov, Andrey F.

2018-05-01

Recent observation of quantum vortices in superfluid 4He droplets measuring a few hundreds of nanometers in diameter involved decoration of vortex cores by clusters containing large numbers of Xe atoms, which served as X-ray contrast agents. Here, we report on the study of the kinematics of the combined vortex-cluster system in a cylinder and in a sphere. Equilibrium states, characterized by total angular momentum, L, were found by minimizing the total energy, E, which sums from the kinetic energy of the liquid due to the vortex and due to orbiting Xe clusters, as well as solvation energy of the cluster in the droplet. Calculations show that, at small mass of the cluster, the equilibrium displacement of the system from the rotation axis is close to that for the bare vortex. However, upon decrease in L beyond certain critical value, which is larger for heavier clusters, the displacement bifurcates toward the surface region, where the motion of the system is governed by the clusters. In addition, at even smaller L, bare orbiting clusters become energetically favorable, opening the possibility for the vortex to detach from the cluster and to annihilate at the droplet's surface.

Evaluation of Vortex Chamber Concepts for Liquid Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Trinh, Huu Phuoc; Knuth, Williams; Michaels, Scott; Turner, James E. (Technical Monitor)

2000-01-01

Rocket-based combined-cycle engines (RBBC) being considered at NASA for future generation launch vehicles feature clusters of small rocket thrusters as part of the engine components. Depending on specific RBBC concepts, these thrusters may be operated at various operating conditions including power level and/or propellant mixture ratio variations. To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for the subject cycle engine application. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concepts not only offer the system simplicity but they also would enhance the combustion performance. The test results showed that the chamber performance was markedly high even at a low chamber length-to- diameter ratio (L/D). This incentive can be translated to a convenience in the thrust chamber packaging.

Large Hysteresis effect in Synchronization of Nanocontact Vortex Oscillators by Microwave Fields

PubMed Central

Perna, S.; Lopez-Diaz, L.; d’Aquino, M.; Serpico, C.

2016-01-01

Current-induced vortex oscillations in an extended thin-film with point-contact geometry are considered. The synchronization of these oscillations with a microwave external magnetic field is investigated by a reduced order model that takes into account the dynamical effects associated with the significant deformation of the vortex structure produced by the current, which cannot be taken care of by using the standard rigid vortex theory. The complete phase diagram of the vortex oscillation dynamics is derived and it is shown that strong hysteretic behavior occurs in the synchronization with the external field. The complex nonlinear nature of the synchronization manifests itself also through the appearance of asymmetry in the locking frequency bands for moderate microwave field amplitudes. Predictions from the reduced order model are confirmed by full micromagnetic simulations. PMID:27538476

Independent Manipulation of Topological Charges and Polarization Patterns of Optical Vortices

PubMed Central

Yang, Ching-Han; Chen, Yuan-Di; Wu, Shing-Trong; Fuh, Andy Ying-Guey

2016-01-01

We present a simple and flexible method to generate various vectorial vortex beams (VVBs) with a Pancharatnam phase based on the scheme of double reflections from a single liquid crystal spatial light modulator (SLM). In this configuration, VVBs are constructed by the superposition of two orthogonally polarized orbital angular momentum (OAM) eigenstates. To verify the optical properties of the generated beams, Stokes polarimetry is developed to measure the states of polarization (SOP) over the transverse plane, while a Shack–Hartmann wavefront sensor is used to measure the OAM charge of beams. It is shown that both the simulated and the experimental results are in good qualitative agreement. In addition, polarization patterns and OAM charges of generated beams can be controlled independently using the proposed method. PMID:27526858

Optical diagnostics and computational modeling of reacting and non-reacting single and multiphase flows

NASA Astrophysics Data System (ADS)

Basu, Saptarshi

Three critical problem domains namely water transport in PEM fuel cell, interaction of vortices with diffusion flames and laminar diffusion layers and thermo-physical processes in droplets heated by a plasma or monochromatic radiation have been analyzed in this dissertation. The first part of the dissertation exhibits a unique, in situ, line-of-sight measurements of water vapor partial pressure and temperature in single and multiple gas channels on the cathode side of an operating PEM fuel cell. Tunable diode laser absorption spectroscopy was employed for these measurements for which water transitions sensitive to temperature and partial pressure were utilized. The technique was demonstrated in a PEM fuel cell operating under both steady state and time-varying load conditions. The second part of the dissertation is dedicated to the study of vortex interaction with laminar diffusion flame and non-reacting diffusion layers. For the non-reacting case, a detailed computational study of scalar mixing in a laminar vortex is presented for vortices generated between two gas streams. A detailed parametric study was conducted to determine the effects of vortex strength, convection time, and non-uniform temperature on scalar mixing characteristics. For the reacting case, an experimental study of the interaction of a planar diffusion flame with a line vortex is presented. The flame-vortex interactions are diagnosed by laser induced incandescence for soot yield and by particle image velocimetry for vortex flow characterization. The soot topography was studied as a function of the vortex strength, residence time, flame curvature and the reactant streams from which vortices are initiated. The third part of the dissertation is modeling of thermo-physical processes in liquid ceramic precursor droplets injected into plasma as used in the thermal spray industry to generate thermal barrier coatings on high value materials. Models include aerodynamic droplet break-up process, mixing of droplets in the high temperature plasma, heat and mass transfer within individual droplets as well as droplet precipitation and internal pressurization. The last part of the work is also concerned with the modeling of thermo-physical processes in liquid ceramic precursor droplets heated by monochromatic radiation. Purpose of this work was to evaluate the feasibility of studying precipitation kinetics and morphological changes in a droplet by mimicking similar heating rates as the plasma.

A Design Tool for Liquid Rocket Engine Injectors

NASA Technical Reports Server (NTRS)

Farmer, R.; Cheng, G.; Trinh, H.; Tucker, K.

2000-01-01

A practical design tool which emphasizes the analysis of flowfields near the injector face of liquid rocket engines has been developed and used to simulate preliminary configurations of NASA's Fastrac and vortex engines. This computational design tool is sufficiently detailed to predict the interactive effects of injector element impingement angles and points and the momenta of the individual orifice flows and the combusting flow which results. In order to simulate a significant number of individual orifices, a homogeneous computational fluid dynamics model was developed. To describe sub- and supercritical liquid and vapor flows, the model utilized thermal and caloric equations of state which were valid over a wide range of pressures and temperatures. The model was constructed such that the local quality of the flow was determined directly. Since both the Fastrac and vortex engines utilize RP-1/LOX propellants, a simplified hydrocarbon combustion model was devised in order to accomplish three-dimensional, multiphase flow simulations. Such a model does not identify drops or their distribution, but it does allow the recirculating flow along the injector face and into the acoustic cavity and the film coolant flow to be accurately predicted.

Propagation dynamics of off-axis symmetrical and asymmetrical vortices embedded in flat-topped beams

NASA Astrophysics Data System (ADS)

Zhang, Xu; Wang, Haiyan

2017-11-01

In this paper, propagation dynamics of off-axis symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams have been explored numerically based on rigorous scalar diffraction theory. The distribution properties of phase and intensity play an important role in driving the propagation dynamics of OVs. Numerical results show that the single off-axis vortex moves in a straight line. The displacement of the single off-axis vortex becomes smaller, when either the order of flatness N and the beam size ω0are increased or the off-axis displacement d is decreased. In addition, the phase singularities of high order vortex beams can be split after propagating a certain distance. It is also demonstrated that the movement of OVs are closely related with the spatial symmetrical or asymmetrical distribution of vortex singularities field. Multiple symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams can interact and rotate. The investment of the propagation dynamics of OVs may have many applications in optical micro-manipulation and optical tweezers.

Orbit-induced localized spin angular momentum in strong focusing of optical vectorial vortex beams

NASA Astrophysics Data System (ADS)

Li, Manman; Cai, Yanan; Yan, Shaohui; Liang, Yansheng; Zhang, Peng; Yao, Baoli

2018-05-01

Light beams may carry optical spin or orbital angular momentum, or both. The spin and orbital parts manifest themselves by the ellipticity of the state of polarization and the vortex structure of phase of light beams, separately. Optical spin and orbit interaction, arising from the interaction between the polarization and the spatial structure of light beams, has attracted enormous interest recently. The optical spin-to-orbital angular momentum conversion under strong focusing is well known, while the converse process, orbital-to-spin conversion, has not been reported so far. In this paper, we predict in theory that the orbital angular momentum can induce a localized spin angular momentum in strong focusing of a spin-free azimuthal polarization vortex beam. This localized longitudinal spin of the focused field can drive the trapped particle to spin around its own axis. This investigation provides a new degree of freedom for spinning particles by using a vortex phase, which may have considerable potentials in optical spin and orbit interaction, light-beam shaping, or optical manipulation.

Vector spherical quasi-Gaussian vortex beams

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2014-02-01

Model equations for describing and efficiently computing the radiation profiles of tightly spherically focused higher-order electromagnetic beams of vortex nature are derived stemming from a vectorial analysis with the complex-source-point method. This solution, termed as a high-order quasi-Gaussian (qG) vortex beam, exactly satisfies the vector Helmholtz and Maxwell's equations. It is characterized by a nonzero integer degree and order (n,m), respectively, an arbitrary waist w0, a diffraction convergence length known as the Rayleigh range zR, and an azimuthal phase dependency in the form of a complex exponential corresponding to a vortex beam. An attractive feature of the high-order solution is the rigorous description of strongly focused (or strongly divergent) vortex wave fields without the need of either the higher-order corrections or the numerically intensive methods. Closed-form expressions and computational results illustrate the analysis and some properties of the high-order qG vortex beams based on the axial and transverse polarization schemes of the vector potentials with emphasis on the beam waist.

Controlling abruptly autofocusing vortex beams to mitigate crosstalk and vortex splitting in free-space optical communication.

PubMed

Yan, Xu; Guo, Lixin; Cheng, Mingjian; Li, Jiangting

2018-05-14

Orbital angular momentum (OAM) mode crosstalk induced by atmospheric turbulence is a challenging phenomenon commonly occurring in OAM-based free-space optical (FSO) communication. Recent advances have facilitated new practicable methods using abruptly autofocusing light beams for weakening the turbulence effect on the FSO link. In this work, we show that a circular phase-locked Airy vortex beam array (AVBA) with sufficient elements has the inherent ability to form an abruptly autofocusing light beam carrying OAM, and its focusing properties can be controlled on demand by adjusting the topological charge values and locations of these vortices embedded in the array elements. The performance of a tailored Airy vortex beam array (TAVBA) through atmospheric turbulence is numerically studied. In a comparison with the ring Airy vortex beam (RAVB), the results indicate that TAVBA can be a superior light source for effectively reducing the intermodal crosstalk and vortex splitting, thus leading to improvement in the FSO system performance.

Liquid mixing enhanced by pulse width modulation in a Y-shaped jet configuration

NASA Astrophysics Data System (ADS)

Xia, Qingfeng; Zhong, Shan

2013-04-01

In this paper, mixing between two fluid streams, which are injected into a planar mixing channel via a Y-shaped confluence section at the same volume flow rate, is studied experimentally. The injection of the two fluid streams is controlled by two separate solenoid valves, which are operated with a phase difference of 180°, using pulse width modulation. The experiments are conducted using water at a mean Reynolds number between 83 and 250, a range of pulsation frequencies and two duty cycles (25 and 50%). Both particle-image velocimetry and planar laser-induced fluorescence technique are used to visualize the flow patterns and to quantify the mixing degree in the mixing channel. This experiment shows that the pulsation of each jet produces vortical structures, which promotes mixing via vortex entrainment and vortex breakup, and at the same time the mixing is also greatly enhanced by sequential segmentation produced by a 180° out-of-phase pulsation of the two jets. This mixing enhancement method is effective at a Reynolds number greater than 125 with a mixing degree of 0.9 being achieved. For the Reynolds numbers studied in the present experiments, an optimal frequency exists, which corresponds to a Strouhal number in the range of 0.5-2. Furthermore, at a given mean Reynolds number a lower duty cycle is found to produce a better mixing due to the resultant higher instantaneous Reynolds number in the jet flow. It is also found that pulsation of only one jet can produce a similar mixing effect.

Experimental and Computational Study of Trapped Vortex Combustor Sector Rig With Tri-Pass Diffuser

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Shouse, D. T.; Roquernore, W. M.; Burrus, D. L.; Duncan, B. S.; Ryder, R. C.; Brankovic, A.; Liu, N.-S.; Gallagher, J. R.; Hendricks, J. A.

2004-01-01

The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL modes of combustion. The present work describes the operational principles of the TVC, and extends diffuser velocities toward choked flow and provides system performance data. Performance data include EINOx results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable compared to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.

Visualization of the collective vortex-like motions in liquid argon and water: Molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Anikeenko, A. V.; Malenkov, G. G.; Naberukhin, Yu. I.

2018-03-01

We propose a new measure of collectivity of molecular motion in the liquid: the average vector of displacement of the particles, ⟨ΔR⟩, which initially have been localized within a sphere of radius Rsph and then have executed the diffusive motion during a time interval Δt. The more correlated the motion of the particles is, the longer will be the vector ⟨ΔR⟩. We visualize the picture of collective motions in molecular dynamics (MD) models of liquids by constructing the ⟨ΔR⟩ vectors and pinning them to the sites of the uniform grid which divides each of the edges of the model box into equal parts. MD models of liquid argon and water have been studied by this method. Qualitatively, the patterns of ⟨ΔR⟩ vectors are similar for these two liquids but differ in minor details. The most important result of our research is the revealing of the aggregates of ⟨ΔR⟩ vectors which have the form of extended flows which sometimes look like the parts of vortices. These vortex-like clusters of ⟨ΔR⟩ vectors have the mesoscopic size (of the order of 10 nm) and persist for tens of picoseconds. Dependence of the ⟨ΔR⟩ vector field on parameters Rsph, Δt, and on the model size has been investigated. This field in the models of liquids differs essentially from that in a random-walk model.

Induction of optical vortex in the crystals subjected to bending stresses.

PubMed

Skab, Ihor; Vasylkiv, Yurij; Vlokh, Rostyslav

2012-08-20

We describe a method for generation of optical vortices that relies on bending of transparent parallelepiped-shaped samples fabricated from either glass or crystalline solid materials. It is shown that the induced singularity of optical indicatrix rotation leads in general to appearance of a mixed screw-edge dislocation of the phase front of outgoing optical beam. At the same time, some specified geometrical parameters of the sample can ensure generation of a purely screw dislocation of the phase front and, as a result, a singly charged canonical optical vortex.

Realization of arbitrarily long focus-depth optical vortices with spiral area-varying zone plates

NASA Astrophysics Data System (ADS)

Zheng, Chenglong; Zang, Huaping; Du, Yanli; Tian, Yongzhi; Ji, Ziwen; Zhang, Jing; Fan, Quanping; Wang, Chuanke; Cao, Leifeng; Liang, Erjun

2018-05-01

We provide a methodology to realize an optical vortex with arbitrarily long focus-depth. With a technique of varying each zone area of a phase spiral zone plate one can obtain optics capable of generating ultra-long focus-depth optical vortex from a plane wave. The focal property of such optics was analysed using the Fresnel diffraction theory, and an experimental demonstration was performed to verify its effectiveness. Such optics may bring new opportunity and benefits for optical vortex application such as optical manipulation and lithography.

A dual-polarized and reconfigurable reflectarray for generation of vortex radio waves

NASA Astrophysics Data System (ADS)

Li, Chen-Chen; Wu, Lin-Sheng; Yin, Wen-Yan

2018-05-01

Electromagnetic (EM) waves with orbital angular momentum (OAM) provide a new degree of freedom for channel multiplexing to improve the capacity of wireless communication. For OAM-based systems, it is important to design specific configurations to generate vortex radios. In this paper, a reconfigurable reflectarray antenna is proposed with independent control of dual polarizations. A reflective cell is proposed by properly assigning the variable capacitances of four varactors, which are placed between metal square rings of each unit. The varactors of each unit are divided into two groups and the capacitance value of each group controls the reflection phase for a single linear polarization. By using the equivalent circuit model, the reflective units and array can be designed efficiently. Smooth phase variation and good reflection efficiency are achieved. Then, the reflectarray is set into sectors and a simple phase-shifting surface model is used to generate vortex beam. Each sector is realized with reflective units satisfying desired reflection phases for different modes. This kind of OAM-generating method can reduce the required variation range of reflection phase and provide more choices for a specific OAM mode combination with dual polarization, which is helpful to reduce mutual coupling between the two linear polarizations. Finally, full-wave simulations show that the 0, ±1, ±2 modes of vortex beam are successfully generated at 3.5 GHz with arbitrary combination in dual-polarization, which is also supported by OAM modes purity and reflection efficiency analysis. Therefore, in our design, the reconfigurable OAM and spin angular momentum (SAM), related with polarization, can be utilized simultaneously and independently for high-capacity wireless communication.

Kinematics, hydrodynamics and energetic advantages of burst-and-coast swimming of koi carps (Cyprinus carpio koi).

PubMed

Wu, Guanhao; Yang, Yan; Zeng, Lijiang

2007-06-01

Koi carps frequently swim in burst-and-coast style, which consists of a burst phase and a coast phase. We quantify the swimming kinematics and the flow patterns generated by the carps in burst-and-coast swimming. In the burst phase, the carps burst in two modes: in the first, the tail beats for at least one cycle (multiple tail-beat mode); in the second, the tail beats for only a half-cycle (half tail-beat mode). The carp generates a vortex ring in each half-cycle beat. The vortex rings generated during bursting in multiple tail-beat mode form a linked chain, but only one vortex ring is generated in half tail-beat mode. The wake morphologies, such as momentum angle and jet angle, also show much difference between the two modes. In the burst phase, the kinematic data and the impulse obtained from the wake are linked to obtain the drag coefficient (C(d,burst) approximately 0.242). In the coast phase, drag coefficient (C(d,coast) approximately 0.060) is estimated from swimming speed deceleration. Our estimation suggests that nearly 45% of energy is saved when burst-and-coast swimming is used by the koi carps compared with steady swimming at the same mean speed.

Vortex-assisted switchable liquid-liquid microextraction for the preconcentration of cadmium in environmental samples prior to its determination with flame atomic absorption spectrometry.

PubMed

Fırat, Merve; Bodur, Süleyman; Tışlı, Büşra; Özlü, Cansu; Chormey, Dotse Selali; Turak, Fatma; Bakırdere, Sezgin

2018-06-12

In this study, a switchable solvent was used to preconcentrate trace amounts of Cd from aqueous solution for its determination by flame atomic absorption spectrometry (FAAS). Protonation of N,N-dimethylbenzylamine by dry ice (solid CO 2 ) made it water soluble, and addition of sodium hydroxide converted it back to its original nonionic state for phase separation and subsequent extraction of Cd. A slotted quartz tube (SQT) was attached to the flame burner head to increase the residence time of Cd atoms in the light path. Under the optimum conditions, limits of detection and quantification were determined as 0.7 and 2.6 μg L -1 , respectively. Low relative standard deviations calculated from seven replicate measurements of the lowest concentration indicated high precision. Accuracy of the developed method was checked by using a standard reference material (SRM 1633c). Spiked recovery tests were also performed on lake water and wastewater samples at different concentrations to check the applicability of the developed method, and the results obtained (90-103%) established high recovery.

Frequency spirals.

PubMed

Ottino-Löffler, Bertrand; Strogatz, Steven H

2016-09-01

We study the dynamics of coupled phase oscillators on a two-dimensional Kuramoto lattice with periodic boundary conditions. For coupling strengths just below the transition to global phase-locking, we find localized spatiotemporal patterns that we call "frequency spirals." These patterns cannot be seen under time averaging; they become visible only when we examine the spatial variation of the oscillators' instantaneous frequencies, where they manifest themselves as two-armed rotating spirals. In the more familiar phase representation, they appear as wobbly periodic patterns surrounding a phase vortex. Unlike the stationary phase vortices seen in magnetic spin systems, or the rotating spiral waves seen in reaction-diffusion systems, frequency spirals librate: the phases of the oscillators surrounding the central vortex move forward and then backward, executing a periodic motion with zero winding number. We construct the simplest frequency spiral and characterize its properties using analytical and numerical methods. Simulations show that frequency spirals in large lattices behave much like this simple prototype.

Quantitative metrics for assessment of chemical image quality and spatial resolution

DOE PAGES

Kertesz, Vilmos; Cahill, John F.; Van Berkel, Gary J.

2016-02-28

Rationale: Currently objective/quantitative descriptions of the quality and spatial resolution of mass spectrometry derived chemical images are not standardized. Development of these standardized metrics is required to objectively describe chemical imaging capabilities of existing and/or new mass spectrometry imaging technologies. Such metrics would allow unbiased judgment of intra-laboratory advancement and/or inter-laboratory comparison for these technologies if used together with standardized surfaces. Methods: We developed two image metrics, viz., chemical image contrast (ChemIC) based on signal-to-noise related statistical measures on chemical image pixels and corrected resolving power factor (cRPF) constructed from statistical analysis of mass-to-charge chronograms across features of interest inmore » an image. These metrics, quantifying chemical image quality and spatial resolution, respectively, were used to evaluate chemical images of a model photoresist patterned surface collected using a laser ablation/liquid vortex capture mass spectrometry imaging system under different instrument operational parameters. Results: The calculated ChemIC and cRPF metrics determined in an unbiased fashion the relative ranking of chemical image quality obtained with the laser ablation/liquid vortex capture mass spectrometry imaging system. These rankings were used to show that both chemical image contrast and spatial resolution deteriorated with increasing surface scan speed, increased lane spacing and decreasing size of surface features. Conclusions: ChemIC and cRPF, respectively, were developed and successfully applied for the objective description of chemical image quality and spatial resolution of chemical images collected from model surfaces using a laser ablation/liquid vortex capture mass spectrometry imaging system.« less

Quantitative metrics for assessment of chemical image quality and spatial resolution

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

Kertesz, Vilmos; Cahill, John F.; Van Berkel, Gary J.

Rationale: Currently objective/quantitative descriptions of the quality and spatial resolution of mass spectrometry derived chemical images are not standardized. Development of these standardized metrics is required to objectively describe chemical imaging capabilities of existing and/or new mass spectrometry imaging technologies. Such metrics would allow unbiased judgment of intra-laboratory advancement and/or inter-laboratory comparison for these technologies if used together with standardized surfaces. Methods: We developed two image metrics, viz., chemical image contrast (ChemIC) based on signal-to-noise related statistical measures on chemical image pixels and corrected resolving power factor (cRPF) constructed from statistical analysis of mass-to-charge chronograms across features of interest inmore » an image. These metrics, quantifying chemical image quality and spatial resolution, respectively, were used to evaluate chemical images of a model photoresist patterned surface collected using a laser ablation/liquid vortex capture mass spectrometry imaging system under different instrument operational parameters. Results: The calculated ChemIC and cRPF metrics determined in an unbiased fashion the relative ranking of chemical image quality obtained with the laser ablation/liquid vortex capture mass spectrometry imaging system. These rankings were used to show that both chemical image contrast and spatial resolution deteriorated with increasing surface scan speed, increased lane spacing and decreasing size of surface features. Conclusions: ChemIC and cRPF, respectively, were developed and successfully applied for the objective description of chemical image quality and spatial resolution of chemical images collected from model surfaces using a laser ablation/liquid vortex capture mass spectrometry imaging system.« less

Vortex Mask: Making 80nm contacts with a twist!

NASA Astrophysics Data System (ADS)

Levenson, Marc D.; Dai, Grace; Ebihara, Takeaki

2002-12-01

An optical vortex has a phase that spirals like a corkscrew. Since any nonzero optical amplitude must have a well-defined phase, the axis of a vortex (where the phase is undefined) is always dark. Printed in negative resist, lowest order vortices would produce contact holes with 0.20.6 can be produced using a chromeless phase-edge mask composed of rectangles with phases of 0°, 90°, 180° and 270°. EMF and Kirchhoff-approximation simulations reveal that the image quality of the dark spots is excellent, and predict a process window with 15% exposure latitude and 400nm DOF for 80nm diameter spots on pitches >=250nm at σ=0.15. EMF simulations predict that the 0-270° phase step will not be excessively dark if the quartz wall is vertical. Chrome spots at the centers can control the diameters which otherwise are set by the parameters of the imaging system and exposure dose. Unwanted vortices can be erased from the image by exposing with a second, more conventional, trim mask. This method would be superior to the other ways of producing sub-wavelength vias, but successful implementation requires the development of appropriate negative-tone resist processes.

Anisotropic superconductivity and elongated vortices with unusual bound states in quasi-one-dimensional nickel-bismuth compounds

NASA Astrophysics Data System (ADS)

Wang, Wen-Lin; Zhang, Yi-Min; Lv, Yan-Feng; Ding, Hao; Wang, Lili; Li, Wei; He, Ke; Song, Can-Li; Ma, Xu-Cun; Xue, Qi-Kun

2018-04-01

We report low-temperature scanning tunneling microscopy and spectroscopy studies of Ni-Bi films grown by molecular beam epitaxy. Highly anisotropic and twofold symmetric superconducting gaps are revealed in two distinct composites, Bi-rich NiBi3 and near-equimolar NixBi , both sharing quasi-one-dimensional crystal structure. We further reveal axially elongated vortices in both phases, but Caroli-de Gennes-Matricon states solely within the vortex cores of NiBi3. Intriguingly, although the localized bound state splits energetically off at a finite distance ˜10 nm away from a vortex center along the minor axis of elliptic vortex, no splitting is found along the major axis. We attribute the elongated vortices and unusual vortex behaviors to the combined effects of twofold superconducting gap and Fermi velocity. The findings provide a comprehensive understanding of the electron pairing and vortex matter in quasi-one-dimensional superconductors.

Vortex states in a submicron Bi2212 crystal probed by intrinsic Josephson junctions

NASA Astrophysics Data System (ADS)

Ooi, S.; Tachiki, M.; Mochiku, T.; Wang, H. B.; Komori, K.; Hirata, K.; Arisawa, S.

2018-03-01

To study the pancake-vortex states confined in a submicron Bi2Sr2CaCu2O8+y (Bi2212) crystal, we have measured the c-axis resistance and I-V characteristics of a stack of intrinsic Josephson junctions with a lateral dimension less than 1 µm. Although the stack was accidentally shunted by a parallel resistance of 7.5 kΩ, the I-V characteristics show homogeneous multiple branches after the subtraction of the component. The penetrations of single vortices into the submicron stack were clearly observed in the resistance measurements. A vortex phase diagram was constructed by mapping the c-axis resistance on an H-T plane. Temperature dependence of the first-vortex penetration field is consistent with the theoretical estimation on the formation of a pancake-vortex stack in the center of a superconducting strip.

Vortex flow during early and late left ventricular filling in normal subjects: quantitative characterization using retrospectively-gated 4D flow cardiovascular magnetic resonance and three-dimensional vortex core analysis.

PubMed

Elbaz, Mohammed S M; Calkoen, Emmeline E; Westenberg, Jos J M; Lelieveldt, Boudewijn P F; Roest, Arno A W; van der Geest, Rob J

2014-09-27

LV diastolic vortex formation has been suggested to critically contribute to efficient blood pumping function, while altered vortex formation has been associated with LV pathologies. Therefore, quantitative characterization of vortex flow might provide a novel objective tool for evaluating LV function. The objectives of this study were 1) assess feasibility of vortex flow analysis during both early and late diastolic filling in vivo in normal subjects using 4D Flow cardiovascular magnetic resonance (CMR) with retrospective cardiac gating and 3D vortex core analysis 2) establish normal quantitative parameters characterizing 3D LV vortex flow during both early and late ventricular filling in normal subjects. With full ethical approval, twenty-four healthy volunteers (mean age: 20±10 years) underwent whole-heart 4D Flow CMR. The Lambda2-method was used to extract 3D LV vortex ring cores from the blood flow velocity field during early (E) and late (A) diastolic filling. The 3D location of the center of vortex ring core was characterized using cylindrical cardiac coordinates (Circumferential, Longitudinal (L), Radial (R)). Comparison between E and A filling was done with a paired T-test. The orientation of the vortex ring core was measured and the ring shape was quantified by the circularity index (CI). Finally, the Spearman's correlation between the shapes of mitral inflow pattern and formed vortex ring cores was tested. Distinct E- and A-vortex ring cores were observed with centers of A-vortex rings significantly closer to the mitral valve annulus (E-vortex L=0.19±0.04 versus A-vortex L=0.15±0.05; p=0.0001), closer to the ventricle's long-axis (E-vortex: R=0.27±0.07, A-vortex: R=0.20±0.09, p=0.048) and more elliptical in shape (E-vortex: CI=0.79±0.09, A-vortex: CI=0.57±0.06; <0.001) compared to E-vortex. The circumferential location and orientation relative to LV long-axis for both E- and A-vortex ring cores were similar. Good to strong correlation was found between vortex shape and mitral inflow shape through both the annulus (r=0.66) and leaflet tips (r=0.83). Quantitative characterization and comparison of 3D vortex rings in LV inflow during both early and late diastolic phases is feasible in normal subjects using retrospectively-gated 4D Flow CMR, with distinct differences between early and late diastolic vortex rings.

Vortex-assisted surfactant-enhanced emulsification microextraction based on solidification of floating organic drop combined with high performance liquid chromatography for determination of naproxen and nabumetone.

PubMed

Asadi, Mohammad; Haji Shabani, Ali Mohammad; Dadfarnia, Shayessteh; Abbasi, Bijan

2015-12-18

A novel, rapid, simple and green vortex-assisted surfactant-enhanced emulsification microextraction method based on solidification of floating organic drop was developed for simultaneous separation/preconcentration and determination of ultra trace amounts of naproxen and nabumetone with high performance liquid chromatography-fluorescence detection. Some parameters influencing the extraction efficiency of analytes such as type and volume of extractant, type and concentration of surfactant, sample pH, KCl concentration, sample volume, and vortex time were investigated and optimized. Under optimal conditions, the calibration graph exhibited linearity in the range of 3.0-300.0ngL(-1) for naproxen and 7.0-300.0ngL(-1) for nabumetone with a good coefficient of determination (R(2)>0.999). The limits of detection were 0.9 and 2.1ngL(-1). The relative standard deviations for inter- and intra-day assays were in the range of 5.8-10.1% and 3.8-6.1%, respectively. The method was applied to the determination of naproxen and nabumetone in urine, water, wastewater and milk samples and the accuracy was evaluated through recovery experiments. Copyright © 2015 Elsevier B.V. All rights reserved.

Ancrage des vortex dans les supraconducteurs Description phénoménologique de la réponse linéaire d'un de vortex ancré

NASA Astrophysics Data System (ADS)

Lütke-Entrup, N.; Plaçais, B.; Mathieu, P.; Simon, Y.

Vortices pinning in supraconductors In this article we report on the investigation of the dynamics of vortices based on the high frequency linear response. We present a serie of measurements of the complex penetration depth in the mixed state in a variety of samples, including conventional materials (Nb, V, PbIn), the non-conventional heavy fermion UPt3, and the high-T_c cuprate YBaCuO. We have explored a large frequency range (1 kHz 10 MHz) so as to cover the cross-over from the quasi-static response, which is dominated by elastic interactions between vortices and sample defects, to the high-frequency regime, which is governed by viscous damping due to vortex friction against the host crystal. For a quantitative description of the frequency spectrum we start from a phenomenological theory which makes a rigorous distinction between vortex lines, along a vortex field omega, and magnetic field lines B. It predicts a second electrodynamical mode, which is linked to the vortex line tension and has a rather short range. We show that, in the limit of small vortex oscillations, amplitude and phase of the linear response are governed by an additional boundary condition for the vortex lattice at the sample surface ; it takes the form of a slipping condition with a characteristic length that depends on the surface roughness. The frequency spectrum deduced from this mechanism is clearly different from the Campbell spectrum, which is the common signature of all bulk pinning mechanisms. Our results on samples of PbIn, Nb, V, and YBaCuO entirely confirm our model, including some non-intuitive size effects which appear at low frequency when the sample becomes transparent to the flux flow mode. However, our measurements in the B and C phases of UPt3 reveal and important contribution of the bulk to the vortex pinning. Ce travail porte sur l'étude de l'ancrage des vortex par la réponse linéaire haute fréquence. Nous présentons une série de mesures de la profondeur de pénétration complexe dans l'état mixte sur une variété d'échantillons qui va des supraconducteurs classiques (Nb, V, PbIn), aux composés de fermions lourds non-conventionnels (UPt3), en passant par les cuprates à haute température critique (YBaCuO). La large gamme des fréquences explorées (1 kHz 10 MHz) permet de couvrir le changement de régime entre la réponse quasistatique dominée par l'interaction élastique des vortex avec les défauts, et la réponse haute fréquence amortie par la friction visqueuse du réseau de vortex au cristal ionique. Pour décrire quantitativement le spectre de fréquence, nous nous appuyons sur une théorie phénoménologique qui fait une distinction explicite et rigoureuse entre lignes de vortex, décrites par un champ omega, et lignes de champ magnétique B. On prédit ainsi l'existence d'un second mode électrodynamique, évanescent et de courte portée, lié à la tension de ligne des vortex. On montre que la réponse aux petits mouvements, amplitude et phase, est réglée par une condition limite supplémentaire sur le réseau de vortex à la surface ; elle prend la forme d'une condition de glissement avec une longueur phénoménologique contrôlée par la rugosité de l'échantillon. Le spectre de fréquence associé à ce mécanisme se distingue nettement du spectre de Campbell, générique des modèles d'ancrage en volume. Nos mesures sur des échantillons PbIn, Nb, V et YBaCuO confirment entièrement notre modèle, y compris des effets de taille peu intuitifs qui se produisent à basse fréquence quand l'échantillon devient transparent au mode flux flow. En revanche, l'étude des vortex dans les phases B et C d'UPt3 montre une contribution importante du volume à l'ancrage des vortex.

Crossflow Stability and Transition Experiments in a Swept-Wing Flow. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Dagenhart, John Ray

1992-01-01

An experimental examination of crossflow instability and transition on a 45 degree swept wing is conducted in the Arizona State University Unsteady Wind Tunnel. The stationary-vortex pattern and transition location are visualized using both sublimating-chemical and liquid-crystal coatings. Extensive hot-wire measurements are conducted at several measurement stations across a single vortex track. The mean and travelling-wave disturbances are measured simultaneously. Stationary-crossflow disturbance profiles are determined by subtracting either a reference or a span-averaged velocity profile from the mean-velocity data. Mean, stationary-crossflow, and travelling-wave velocity data are presented as local boundary-layer profiles and as contour plots across a single stationary-crossflow vortex track. Disturbance-mode profiles and growth rates are determined. The experimental data are compared to predictions from linear stability theory.

Vortex-ultrasound-assisted dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry for the analysis of volatile bioactive components and comparative pharmacokinetic study of the herb-herb interactions in Guanxin Shutong Capsule.

PubMed

Mu, Jingqing; Gao, Xun; Li, Qing; Yang, Xiaomei; Yang, Wenling; Sun, Xu; Bi, Kaishun; Zhang, Huifen

2017-08-01

Guanxin Shutong Capsule, an effective traditional Chinese medicine, is widely used for coronary heart disease clinically. Volatile components are one of its important bioactive constituents. To better understand the material basis for the therapeutic effects, the components of Guanxin Shutong Capsule absorbed into the blood and their metabolites were identified based on gas chromatography with mass spectrometry coupled with vortex-ultrasound-assisted dispersive liquid-liquid microextraction. As a result, three prototypes and 15 metabolites were identified or tentatively characterized in rat plasma. Subsequently, a pharmacokinetic study was carried out to monitor the concentrations of the main bioactive constituents and metabolites (isoborneol, borneol, eugenol, and camphor) by gas chromatography with mass spectrometry in rat plasma following oral administration of single herb extract and different combinations of herbs in this prescription. Compared to other groups, a statistically significant difference of the pharmacokinetic properties was obtained when the total complex prescription was administered, indicating possible drug-drug interactions among the complex ingredients of Guanxin Shutong Capsule. These findings provided an experimental basis concerning the clinical application and medicinal efficacy of Guanxin Shutong Capsule in the treatment of coronary heart disease. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Non-Abelian vortex lattices

NASA Astrophysics Data System (ADS)

Tallarita, Gianni; Peterson, Adam

2018-04-01

We perform a numerical study of the phase diagram of the model proposed in [M. Shifman, Phys. Rev. D 87, 025025 (2013)., 10.1103/PhysRevD.87.025025], which is a simple model containing non-Abelian vortices. As per the case of Abrikosov vortices, we map out a region of parameter space in which the system prefers the formation of vortices in ordered lattice structures. These are generalizations of Abrikosov vortex lattices with extra orientational moduli in the vortex cores. At sufficiently large lattice spacing the low energy theory is described by a sum of C P (1 ) theories, each located on a vortex site. As the lattice spacing becomes smaller, when the self-interaction of the orientational field becomes relevant, only an overall rotation in internal space survives.

Ignition and structure of a laminar diffusion flame in the field of a vortex

NASA Technical Reports Server (NTRS)

Macaraeg, Michele G.; Jackson, T. L.; Hussaini, M. Y.

1991-01-01

The distortion of flames in flows with vortical motion is examined via asymptotic analysis and numerical simulation. The model consists of a constant density, one step, irreversible Arrhenius reaction between initially unmixed species occupying adjacent half-planes which are then allowed to mix and react in the presence of a vortex. The evolution in time of the temperature and mass fraction fields is followed. Emphasis is placed on the ignition time and location as a function of vortex Reynolds number and initial temperature differences of the reacting species. The study brings out the influence of the vortex on the chemical reaction. In all phases, good agreement is observed between asymptotic analysis and the full numerical solution of the model equations.

RAPID COMMUNICATION Time-resolved measurements with a vortex flowmeter in a pulsating turbulent flow using wavelet analysis

NASA Astrophysics Data System (ADS)

Laurantzon, F.; Örlü, R.; Segalini, A.; Alfredsson, P. H.

2010-12-01

Vortex flowmeters are commonly employed in technical applications and are obtainable in a variety of commercially available types. However their robustness and accuracy can easily be impaired by environmental conditions, such as inflow disturbances and/or pulsating conditions. Various post-processing techniques of the vortex signal have been used, but all of these methods are so far targeted on obtaining an improved estimate of the time-averaged bulk velocity. Here, on the other hand, we propose, based on wavelet analysis, a straightforward way to utilize the signal from a vortex shedder to extract the time-resolved and thereby the phase-averaged velocity under pulsatile flow conditions. The method was verified with hot-wire and laser Doppler velocimetry measurements.

Generation of cylindrically polarized vector vortex beams with digital micromirror device

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

Gong, Lei; Liu, Weiwei; Wang, Meng

We propose a novel technique to directly transform a linearly polarized Gaussian beam into vector-vortex beams with various spatial patterns. Full high-quality control of amplitude and phase is implemented via a Digital Micro-mirror Device (DMD) binary holography for generating Laguerre-Gaussian, Bessel-Gaussian, and helical Mathieu–Gaussian modes, while a radial polarization converter (S-waveplate) is employed to effectively convert the optical vortices into cylindrically polarized vortex beams. Additionally, the generated vector-vortex beams maintain their polarization symmetry after arbitrary polarization manipulation. Due to the high frame rates of DMD, rapid switching among a series of vector modes carrying different orbital angular momenta paves themore » way for optical microscopy, trapping, and communication.« less

On the formation of vortex rings in coaxial tubes

NASA Astrophysics Data System (ADS)

Gan, Lian

2011-11-01

The formation of vortex rings within coaxial tubes of different diameter is investigated experimentally and numerically. PIV measurements were carried out in a water tank equipped with a piston-cylinder apparatus used to generate vortex rings inside a series of coaxial tubes with tube to piston diameter ratios, DT / D , ranging from 4 to 1.5. In order to distinguish between the effect confinement has on the formation of isolated vortex rings from those formed with a trailing jet flow, non- dimensional stroke ratios below and above the formation number were investigated, L / D = 2 . 5 and 10 respectively. For DT / D > 2 and L / D s below the formation number the kinematics of the vortex rings follow classical inviscid theory in so much as their self-induced velocity decreases linearly with decreasing tube diameter in accordance with the image theorem. For DT / D <= 2 boundary layer separation along the tube wall begins to interfere with the vortex during its roll-up phase. For vortex rings below the formation number, the vortex core is briefly arrested upon completion of the piston stroke. On the other hand, long L / D s give rise to even more complex dynamics. When DT / D = 2 the interaction between boundary layer and the starting jet acts to suppress vortex ring formation altogether. However, as confinement is increased further to DT / D = 1 . 5 the formation of a lead vortex ring re-appears but with a circulation lower than the formation number before rapidly decaying.

Vortices in a rotating two-component Bose–Einstein condensate with tunable interactions and harmonic potential

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

Zhang, Xiao-Fei, E-mail: xfzhang@ntsc.ac.cn; Du, Zhi-Jing; Tan, Ren-Bing

We consider a pair of coupled nonlinear Schrödinger equations modeling a rotating two-component Bose–Einstein condensate with tunable interactions and harmonic potential, with emphasis on the structure of vortex states by varying the strength of inter-component interaction, rotational frequency, and the aspect ratio of the harmonic potential. Our results show that the inter-component interaction greatly enhances the effect of rotation. For the case of isotropic harmonic potential and small inter-component interaction, the initial vortex structure remains unchanged. As the ratio of inter- to intra-component interactions increases, each component undergoes a transition from a vortex lattice (vortex line) in an isotropic (anisotropic)more » harmonic potential to an alternatively arranged stripe pattern, and eventually to the interwoven “serpentine” vortex sheets. Moreover, in the case of anisotropic harmonic potential the system can develop to a rotating droplet structure. -- Highlights: •Different vortex structures are obtained within the full parameter space. •Effects of system parameters on the ground state structure are discussed. •Phase transition between different vortex structures is also examined. •Present one possible way to obtain the rotating droplet structure. •Provide many possibilities to manipulate vortex in two-component BEC.« less

Nonlinear ion acoustic waves scattered by vortexes

NASA Astrophysics Data System (ADS)

Ohno, Yuji; Yoshida, Zensho

2016-09-01

The Kadomtsev-Petviashvili (KP) hierarchy is the archetype of infinite-dimensional integrable systems, which describes nonlinear ion acoustic waves in two-dimensional space. This remarkably ordered system resides on a singular submanifold (leaf) embedded in a larger phase space of more general ion acoustic waves (low-frequency electrostatic perturbations). The KP hierarchy is characterized not only by small amplitudes but also by irrotational (zero-vorticity) velocity fields. In fact, the KP equation is derived by eliminating vorticity at every order of the reductive perturbation. Here, we modify the scaling of the velocity field so as to introduce a vortex term. The newly derived system of equations consists of a generalized three-dimensional KP equation and a two-dimensional vortex equation. The former describes 'scattering' of vortex-free waves by ambient vortexes that are determined by the latter. We say that the vortexes are 'ambient' because they do not receive reciprocal reactions from the waves (i.e., the vortex equation is independent of the wave fields). This model describes a minimal departure from the integrable KP system. By the Painlevé test, we delineate how the vorticity term violates integrability, bringing about an essential three-dimensionality to the solutions. By numerical simulation, we show how the solitons are scattered by vortexes and become chaotic.

Comment on ``Symmetry and structure of quantized vortices in superfluid 3'

NASA Astrophysics Data System (ADS)

Sauls, J. A.; Serene, J. W.

1985-10-01

Recent theoretical attempts to explain the observed vortex-core phase transition in superfluid 3B yield conflicting results. Variational calculations by Fetter and Theodrakis, based on realistic strong-coupling parameters, yield a phase transition in the Ginzburg-Landau region that is in qualitative agreement with the phase diagram. Numerically precise calculations by Salomaa and Volivil (SV), based on the Brinkman-Serene-Anderson (BSA) parameters, do not yield a phase transition between axially symmetric vortices. The ambiguity of these results is in part due to the large differences between the β parameters, which are inputs to the vortex free-energy functional. We comment on the relative merits of the β parameters based on recent improvements in the quasiparticle scattering amplitude and the BSA parameters used by SV.

Modeling the Frozen-In Anticyclone in the 2005 Arctic Summer Stratosphere

NASA Technical Reports Server (NTRS)

Allen, D. R.; Douglass, A. R.; Manney, G. L.; Strahan, S. E.; Krosschell, J. C.; Trueblood, J.

2010-01-01

Immediately following the breakup of the 2005 Arctic spring stratospheric vortex, a tropical air mass, characterized by low potential vorticity (PV) and high nitrous oxide (N2O), was advected poleward and became trapped in the easterly summer polar vortex. This feature, known as a "Frozen-In Anticyclone (FrIAC)", was observed in Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) data to span the potential temperature range from approximately 580 to 1100 K (approximately 25 to 40 km altitude) and to persist from late March to late August 2005. This study compares MLS N2O observations with simulations from the Global Modeling Initiative (GMI) chemistry and transport model, the GEOS-5/MERRA Replay model, and the VanLeer Icosahedral Triangular Advection isentropic transport model to elucidate the processes involved in the lifecycle of the FrIAC which is here divided into three distinct phases. During the "spin-up phase" (March to early April), strong poleward flow resulted in a tight isolated anticyclonic vortex at approximately 70-90 deg N, marked with elevated N2O. GMI, Replay, and VITA all reliably simulted the spin-up of the FrIAC, although the GMI and Replay peak N2O values were too low. The FrIAC became trapped in the developing summer easterly flow and circulated around the polar region during the "anticyclonic phase" (early April to the end of May). During this phase, the FrIAC crossed directly over the pole between the 7th and 14th of April. The VITA and Replay simulations transported the N2O anomaly intact during this crossing, in agreement with MLS, but unrealistic dispersion of the anomaly occurred in the GMI simulation due to excessive numerical mixing of the polar cap. The vortex associated with the FrIAC was apparently resistant to the weak vertical hear during the anticyclonic phase, and it thereby protected the embedded N20 anomaly from stretching. The vortex decayed in late May due to diabatic processes, leaving the N2O anomaly exposed to horizontal and vertical wind shears during the "shearing phase" (June to August). The observed lifetime of the FrIAC during this phase is consistent with time-scales calculated from the ambient horizontal and vertical wind shear. Replay maintained the horizontal structure of the N2O anomaly similar to NILS well into August. The VITA simulation also captured the horizontal structure of the FrIAC during this phase, but VITA eventually developed fine-scale N2O structure not observed in MLS data.

Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates.

PubMed

Yang, Tao; Hu, Zhi-Qiang; Zou, Shan; Liu, Wu-Ming

2016-07-28

Dynamics of vortex clusters is essential for understanding diverse superfluid phenomena. In this paper, we examine the dynamics of vortex quadrupoles in a trapped two-dimensional (2D) Bose-Einstein condensate. We find that the movement of these vortex-clusters fall into three distinct regimes which are fully described by the radial positions of the vortices in a 2D isotropic harmonic trap, or by the major radius (minor radius) of the elliptical equipotential lines decided by the vortex positions in a 2D anisotropic harmonic trap. In the "recombination" and "exchange" regimes the quadrupole structure maintains, while the vortices annihilate each other permanently in the "annihilation" regime. We find that the mechanism of the charge flipping in the "exchange" regime and the disappearance of the quadrupole structure in the "annihilation" regime are both through an intermediate state where two vortex dipoles connected through a soliton ring. We give the parameter ranges for these three regimes in coordinate space for a specific initial configuration and phase diagram of the vortex positions with respect to the Thomas-Fermi radius of the condensate. We show that the results are also applicable to systems with quantum fluctuations for the short-time evolution.

On the electron vortex beam wavefunction within a crystal.

PubMed

Mendis, B G

2015-10-01

Electron vortex beams are distorted by scattering within a crystal, so that the wavefunction can effectively be decomposed into many vortex components. Using a Bloch wave approach equations are derived for vortex beam decomposition at any given depth and with respect to any frame of reference. In the kinematic limit (small specimen thickness) scattering largely takes place at the neighbouring atom columns with a local phase change of π/2rad. When viewed along the beam propagation direction only one vortex component is present at the specimen entrance surface (i.e. the 'free space' vortex in vacuum), but at larger depths the probe is in a mixed state due to Bragg scattering. Simulations show that there is no direct correlation between vortex components and the 〈Lz〉 pendellösung, i.e. at a given depth probes with relatively constant 〈Lz〉 can be in a more mixed state compared to those with more rapidly varying 〈Lz〉. This suggests that minimising oscillations in the 〈Lz〉 pendellösung by probe channelling is not the only criterion for generating a strong electron energy loss magnetic circular dichroism (EMCD) signal. Copyright © 2015 Elsevier B.V. All rights reserved.

Crystallized and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates

PubMed Central

Liu, Chao-Fei; Fan, Heng; Gou, Shih-Chuan; Liu, Wu-Ming

2014-01-01

Vortex is a topological defect with a quantized winding number of the phase in superfluids and superconductors. Here, we investigate the crystallized (triangular, square, honeycomb) and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates (BECs) by using the damped projected Gross-Pitaevskii equation. The amorphous vortices are the result of the considerable deviation induced by the interaction of atomic-molecular vortices. By changing the atom-molecule interaction from attractive to repulsive, the configuration of vortices can change from an overlapped atomic-molecular vortices to carbon-dioxide-type ones, then to atomic vortices with interstitial molecular vortices, and finally into independent separated ones. The Raman detuning can tune the ratio of the atomic vortex to the molecular vortex. We provide a phase diagram of vortices in rotating atomic-molecular BECs as a function of Raman detuning and the strength of atom-molecule interaction. PMID:24573303

Vortex Loops at the Superfluid Lambda Transition: An Exact Theory?

NASA Technical Reports Server (NTRS)

Williams, Gary A.

2003-01-01

A vortex-loop theory of the superfluid lambda transition has been developed over the last decade, with many results in agreement with experiments. It is a very simple theory, consisting of just three basic equations. When it was first proposed the main uncertainty in the theory was the use Flory scaling to find the fractal dimension of the random-walking vortex loops. Recent developments in high-resolution Monte Carlo simulations have now made it possible to verify the accuracy of this Flory-scaling assumption. Although the loop theory is not yet rigorously proven to be exact, the Monte Carlo results show at the least that it is an extremely good approximation. Recent loop calculations of the critical Casimir effect in helium films in the superfluid phase T < Tc will be compared with similar perturbative RG calculations in the normal phase T > Tc; the two calculations are found to match very nicely right at Tc.

Direct Adaptive Rejection of Vortex-Induced Disturbances for a Powered SPAR Platform

NASA Technical Reports Server (NTRS)

VanZwieten, Tannen S.; Balas, Mark J.; VanZwieten, James H.; Driscoll, Frederick R.

2009-01-01

The Rapidly Deployable Stable Platform (RDSP) is a novel vessel designed to be a reconfigurable, stable at-sea platform. It consists of a detachable catamaran and spar, performing missions with the spar extending vertically below the catamaran and hoisting it completely out of the water. Multiple thrusters located along the spar allow it to be actively controlled in this configuration. A controller is presented in this work that uses an adaptive feedback algorithm in conjunction with Direct Adaptive Disturbance Rejection (DADR) to mitigate persistent, vortex-induced disturbances. Given the frequency of a disturbance, the nominal DADR scheme adaptively compensates for its unknown amplitude and phase. This algorithm is extended to adapt to a disturbance frequency that is only coarsely known by including a Phase Locked Loop (PLL). The PLL improves the frequency estimate on-line, allowing the modified controller to reduce vortex-induced motions by more than 95% using achievable thrust inputs.

Formation of high-order acoustic Bessel beams by spiral diffraction gratings

NASA Astrophysics Data System (ADS)

Jiménez, Noé; Picó, R.; Sánchez-Morcillo, V.; Romero-García, V.; García-Raffi, L. M.; Staliunas, K.

2016-11-01

The formation of high-order Bessel beams by a passive acoustic device consisting of an Archimedes' spiral diffraction grating is theoretically, numerically, and experimentally reported in this paper. These beams are propagation-invariant solutions of the Helmholtz equation and are characterized by an azimuthal variation of the phase along its annular spectrum producing an acoustic vortex in the near field. In our system, the scattering of plane acoustic waves by the spiral grating leads to the formation of the acoustic vortex with zero pressure on axis and the angular phase dislocations characterized by the spiral geometry. The order of the generated Bessel beam and, as a consequence, the size of the generated vortex can be fixed by the number of arms in the spiral diffraction grating. The obtained results allow for obtaining Bessel beams with controllable vorticity by a passive device, which has potential applications in low-cost acoustic tweezers and acoustic radiation force devices.

Effect of Quenched Disorder in the Entropy-Jump at the First-Order Vortex Phase Transition of Bi $_{2} 2 Sr _{2} 2 CaCu _{2} 2 O _{8 + delta }$ 8 + δ

NASA Astrophysics Data System (ADS)

Dolz, M. I.; Pedrazzini, P.; Pastoriza, H.; Konczykowski, M.; Fasano, Y.

2015-04-01

We study the effect of quenched disorder in the thermodynamic magnitudes entailed in the first-order vortex phase transition of the extremely layered BiSrCaCuO compound. We track the temperature-evolution of the enthalpy and the entropy jump at the vortex solidification transition by means of AC local magnetic measurements. Quenched disorder is introduced to the pristine samples by means of heavy-ion irradiation with Pb and Xe producing a random columnar-track pins distribution with different densities (matching field ). In contrast with previous magneto-optical reports, we find that the first-order phase transition persists for samples with up to 100 Gauss. For very low densities of quenched disorder (pristine samples), the evolution of the thermodynamic properties can be satisfactorily explained considering a negligible effect of pinning and only electromagnetic coupling between pancake vortices lying in adjacent CuO planes. This description is not satisfactory on increasing magnitude of quenched disorder.

How robust is the Holton-Tan relationship?

NASA Astrophysics Data System (ADS)

Braesicke, Peter; Kerzenmacher, Tobias

2017-04-01

The Holton-Tan relationship explains a possible link between tropical and extratropical variability (foremost in the northern hemisphere). The idea can be rationalised using simple linear wave theory. The quasi-biennial oscillation in the tropical lower stratosphere can be regarded as a kind of switch that influences the propagation of planetary waves. In a westerly phase of the QBO planetary waves in the stratosphere can propagate more equatorward and the polar vortex remains strong and undisturbed. In an easterly phase of the QBO the propagation is more poleward and the polar vortex is weaker and more disturbed. However, the robustness of this relationship depends on the precise definition of the QBO phase and the criteria used to define the polar vortex strength. Here, we will revisit the basic Holton-Tan relationship and will explore how other factors (including the state of the El Nino-Southern Oscillation) modify the relationship. Using reanalysis data and idealised model experiments a possible range for robust manifestations of the Holton-Tan relationship is determined, thus providing an improved framework for a better understanding of teleconnections between tropical and polar latitudes.

The behavior of a macroscopic granular material in vortex flow

NASA Astrophysics Data System (ADS)

Nishikawa, Asami

A granular material is defined as a collection of discrete particles such as powder and grain. Granular materials display a large number of complex behaviors. In this project, the behavior of macroscopic granular materials under tornado-like vortex airflow, with varying airflow velocity, was observed and studied. The experimental system was composed of a 9.20-cm inner diameter acrylic pipe with a metal mesh bottom holding the particles, a PVC duct, and an airflow source controlled by a variable auto-transformer, and a power-meter. A fixed fan blade was attached to the duct's inner wall to create a tornado-like vortex airflow from straight flow. As the airflow velocity was increased gradually, the behavior of a set of same-diameter granular materials was observed. The observed behaviors were classified into six phases based on the macroscopic mechanical dynamics. Through this project, we gained insights on the significant parameters for a computer simulation of a similar system by Heath Rice [5]. Comparing computationally and experimentally observed phase diagrams, we can see similar structure. The experimental observations showed the effect of initial arrangement of particles on the phase transitions.

Vortex flux dynamics and harmonic ac magnetic response of Ba(Fe 0.94Ni 0.06) 2As 2 bulk superconductor

DOE PAGES

Nikolo, Martin; Zapf, Vivien S.; Singleton, John; ...

2016-07-22

Vortex dynamics and nonlinear ac response are studied in a Ba(Fe 0.94Ni 0.06) 2As 2( T c= 18.5 K) bulk superconductor in magnetic fields up to 12 T via ac susceptibility measurements of the first ten harmonics. A comprehensive study of the ac magnetic susceptibility and its first ten harmonics finds shifts to higher temperatures with increasing ac measurement frequencies (10 to 10,000 Hz) for a wide range of ac (1, 5, and 10 Oe) and dc fields (0 to 12 T). The characteristic measurement time constant t1 is extracted from the exponential fit of the data and linked tomore » vortex relaxation. The Anderson-Kim Arrhenius law is applied to determine flux activation energy E a/k as a function dc magnetic field. The de-pinning, or irreversibility lines, were determined by a variety of methods and extensively mapped. The ac response shows surprisingly weak higher harmonic components, suggesting weak nonlinear behavior. Lastly, our data does not support the Fisher model; we do not see an abrupt vortex glass to vortex liquid transition and the resistivity does not drop to zero, although it appears to approach zero exponentially.« less

Effect of cavitation on flow structure of a tip vortex

NASA Astrophysics Data System (ADS)

Matthieu, Dreyer; Reclari, Martino; Farhat, Mohamed

2013-11-01

Tip vortices, which may develop in axial turbines and marine propellers, are often associated with the occurrence of cavitation because of the low pressure in their core. Although this issue has received a great deal of attention, it is still unclear how the phase transition affects the flow structure of such a vortex. In the present work, we investigate the change of the vortex structure due to cavitation incipience. The measurement of the velocity field is performed in the case of a tip vortex generated by an elliptical hydrofoil placed in the test section of EPFL high speed cavitation tunnel. To this end, a 3D stereo PIV is used with fluorescent seeding particles. A cost effective method is developed to produce in-house fluorescent seeding material, based on polyamide particles and Rhodamine-B dye. The amount of cavitation in the vortex core is controlled by the inlet pressure in the test section, starting with the non-cavitating case. We present an extensive analysis of the vorticity distribution, the vortex intensity and core size for various cavitation developments. This research is supported by CCEM and swisselectric research.

Bright-type and dark-type vector solitons of the (2 + 1)-dimensional spatially modulated quintic nonlinear Schrödinger equation in nonlinear optics and Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Wu, Hong-Yu; Jiang, Li-Hong

2018-03-01

We study a (2 + 1) -dimensional N -coupled quintic nonlinear Schrödinger equation with spatially modulated nonlinearity and transverse modulation in nonlinear optics and Bose-Einstein condensate, and obtain bright-type and dark-type vector multipole as well as vortex soliton solutions. When the modulation depth q is fixed as 0 and 1, we can construct vector multipole and vortex solitons, respectively. Based on these solutions, we investigate the form and phase characteristics of vector multipole and vortex solitons.

Measurements of the scattering of sound by a line vortex

NASA Technical Reports Server (NTRS)

Horne, W. C.

1983-01-01

This paper presents measurements of the phase and magnitude of the scattered field arising from the incidence of a monochromatic plane sound field as a steady vortex. The amplitude of the scattered field was found to vary linearly with the vortex strength, and with the incident wave amplitude and frequency as predicted by solutions based on the Born approximation. The scattered field was observed to be nonsingular in the incidence direction, and this was similar to predictions by the Parabolic Equation Method (PEM) rather than the Born approximation, which predicts singular behavior in the incidence direction.

Comparison and validation of wake vortex characteristics collected at different airports by different scanning lidar sensors

NASA Astrophysics Data System (ADS)

Thobois, Ludovic; Cariou, Jean-Pierre; Cappellazzo, Valerio; Musson, Christian; Treve, Vincent

2018-04-01

Today, the demand for increasing airport capacity is high, in particular for increasing runway throughput from an ATM perspective. Runway capacity is often directly linked with the minima longitudinal separation between aircraft on approach phase or between aircraft on departure. The separation minima are based on surveillance capabilities and on wake turbulence (WT) in order to mitigate respectively collision risk and WT-induced accidents, therefore WT hazard becomes a major concern for ATM. For ten years, many research LIDAR systems have been used for better understanding wake vortices behaviors in the operational environment within large range of wind and turbulence conditions. All these studies[1][2] helped to design new concepts of wake separations between aircrafts thanks to the proven capabilities of LIDAR systems to assess the risks of wake vortex (WV) encounters through the circulation retrievals. The re-categorization project, called RECAT [8], has been launched by a joint EUROCONTROL - FAA initiative in order to renew and optimize the out-of-date currently applied ICAO regulations on distance separation. Nowadays, the first phase of regional RECAT projects, which consists in defining new distance separation matrices composed of six/seven static aircraft categories instead of three, entered the operational phase and is deployed in several airports in United States and Europe. In addition, other concepts like Time-Based Separation have also been studied and deployed in London Heathrow. The airports where these solutions have been deployed obtained significant benefits as increased runway throughput and improved resilience to disruptions. For implementing such new WT solutions at an airport, a local safety assessment before the implementation and a risk monitoring after are usually needed. Before implementation, it may be required to determine for the targeted airport the relative variations of risk of wake vortex encounters, given the local ATM rules, the traffic mix, the weather conditions and their impact on the wake vortex decay. After implementation, the risk monitoring might perform in-depth analysis of wake vortex encounter reported by pilots. For all the mentioned steps, the use of scanning Doppler LIDARs is the only experimental sensor capable of measuring the localization and the circulation of the wake vortices and to provide ground truth wake vortex measurements. Next generation operational LIDARs need to be developed to address in a cost effective way these operational needs. Furthermore, a specific configuration and methodology need to be developed to ensure the accuracy of the wake vortex data. Such a LIDAR based wake vortex solution has been tested at Paris Charles De Gaulle which implemented the RECAT-EU wake separation scheme. The wake vortex circulation, initial spacing and decay measured have been compared to the data collected in London Heathrow by a different LIDAR sensor. The results indicated that the initial circulation, the time to demise, the decay curve evolution and the vortex spacing are very coherent between the two databases.

Contrail Formation in Aircraft Wakes Using Large-Eddy Simulations

NASA Technical Reports Server (NTRS)

Paoli, R.; Helie, J.; Poinsot, T. J.; Ghosal, S.

2002-01-01

In this work we analyze the issue of the formation of condensation trails ("contrails") in the near-field of an aircraft wake. The basic configuration consists in an exhaust engine jet interacting with a wing-tip training vortex. The procedure adopted relies on a mixed Eulerian/Lagrangian two-phase flow approach; a simple micro-physics model for ice growth has been used to couple ice and vapor phases. Large eddy simulations have carried out at a realistic flight Reynolds number to evaluate the effects of turbulent mixing and wake vortex dynamics on ice-growth characteristics and vapor thermodynamic properties.

Quasi-Biennial Oscillation and Solar Cycle Influences over the Winter Arctic Simulated by the WACCM4 Model

NASA Astrophysics Data System (ADS)

Li, K. F.; Limpasuvan, T. L.; Limpasuvan, V.; Tung, K. K.; Yung, Y. L.

2017-12-01

Observations show that the quasi-biennial oscillation (QBO) and the 11-year solar cycle perturb the polar vortex via planetary wave convergence at high latitudes, a mechanism first proposed by Holton and Tan in 1980. Their perturbations lead to increases of stratospheric sudden warming events, and hence observable increases in temperature and ozone abundance in the polar vortex, during the easterly phase of QBO and the solar maximum. Here we simulate the changes in the polar atmosphere using the Whole Atmosphere Community Climate Model 4 (WACCM4) with the prescribed QBO and 11-year solar cycle forcing. The simulation is diagnosed in four groups: westerly QBO phase and solar minimum, westerly QBO phase and solar maximum, easterly QBO phase and solar minimum, and easterly QBO phase and solar maximum. The simulated changes in temperature and ozone are compared with satellite observations.

Force-motion phase relations and aerodynamic performance of a plunging plate

NASA Astrophysics Data System (ADS)

Son, Onur; Cetiner, Oksan

2018-02-01

Due to the unsteady motion of a plunging plate, forces acting on the body experience a phase difference with respect to the motion. These phase relations are investigated experimentally for a harmonically plunging plate within an amplitude range of 0.05≤ {a/c}≤ 0.6, reduced frequency range of 0.78<{k}<7.06, and at a constant Reynolds number of 10,000. Both streamwise and cross-stream force components are found to have a phase lag following the motion; however, their variations are different. The phase lag of the force on the cross-stream direction increases as the amplitude increases. Drag-thrust transition has an influence on the streamwise force phase lags, which starts to increase when the thrust starts to be produced. Particle image velocimetry measurements are also performed to reveal the relations between vortex structures and force measurements. Leading edge vortex shedding characteristics are observed to be changing from drag occurring cases to thrust producing cases in parallel with the increment in phase lags.

Superconducting properties of Ba(Fe1-xNix)2As2 thin films in high magnetic fields

NASA Astrophysics Data System (ADS)

Richter, Stefan; Kurth, Fritz; Iida, Kazumasa; Pervakov, Kirill; Pukenas, Aurimas; Tarantini, Chiara; Jaroszynski, Jan; Hänisch, Jens; Grinenko, Vadim; Skrotzki, Werner; Nielsch, Kornelius; Hühne, Ruben

2017-01-01

We report on the electrical transport properties of epitaxial Ba(Fe1-xNix)2As2 thin films grown by pulsed laser deposition in static magnetic fields up to 35 T. The thin film shows a critical temperature of 17.2 K and a critical current density of 5.7 × 105 A/cm2 in self field at 4.2 K, while the pinning is dominated by elastic pinning at two-dimensional nonmagnetic defects. Compared to the single-crystal data, we find a higher slope of the upper critical field for the thin film at a similar doping level and a small anisotropy. Also, an unusual small vortex liquid phase was observed at low temperatures, which is a striking difference to Co-doped BaFe2As2 thin films.

A minimal model of epithelial tissue dynamics and its application to the corneal epithelium

NASA Astrophysics Data System (ADS)

Henkes, Silke; Matoz-Fernandez, Daniel; Kostanjevec, Kaja; Coburn, Luke; Sknepnek, Rastko; Collinson, J. Martin; Martens, Kirsten

Epithelial cell sheets are characterized by a complex interplay of active drivers, including cell motility, cell division and extrusion. Here we construct a particle-based minimal model tissue with only division/death dynamics and show that it always corresponds to a liquid state with a single dynamic time scale set by the division rate, and that no glassy phase is possible. Building on this, we construct an in-silico model of the mammalian corneal epithelium as such a tissue confined to a hemisphere bordered by the limbal stem cell zone. With added cell motility dynamics we are able to explain the steady-state spiral migration on the cornea, including the central vortex defect, and quantitatively compare it to eyes obtained from mice that are X-inactivation mosaic for LacZ.

Route to non-Abelian quantum turbulence in spinor Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Mawson, Thomas; Ruben, Gary; Simula, Tapio

2015-06-01

We have studied computationally the collision dynamics of spin-2 Bose-Einstein condensates initially confined in a triple-well trap. Depending on the phase structure of the initial-state spinor wave function, the collision of the three condensate fragments produces one of many possible vortex-antivortex lattices, after which the system transitions to quantum turbulence. We find that the emerging vortex lattice structures can be described in terms of multiwave interference. We show that the three-fragment collisions can be used to systematically produce staggered vortex-antivortex honeycomb lattices of fractional-charge vortices, whose collision dynamics are known to be non-Abelian. Such condensate collider experiments could potentially be used as a controllable pathway to generating non-Abelian superfluid turbulence with networks of vortex rungs.

Cascade of Solitonic Excitations in a Superfluid Fermi Gas: From Solitons and Vortex Rings to Solitonic Vortices

NASA Astrophysics Data System (ADS)

Ku, Mark; Mukherjee, Biswaroop; Yefsah, Tarik; Zwierlein, Martin

2015-05-01

We follow the evolution of a superfluid Fermi gas of 6Li atoms following a one-sided π phase imprint. Via tomographic imaging, we observe the formation of a planar dark soliton, and its subsequent snaking and decay into a vortex ring. The latter eventually breaks at the boundary of the superfluid, finally leaving behind a single, remnant solitonic vortex. The nodal surface is directly imaged and reveals its decay into a vortex ring via a puncture of the initial soliton plane. At intermediate stages we find evidence for more exotic structures resembling Φ-solitons. The observed evolution of the nodal surface represents dynamics that occurs at the length scale of the interparticle spacing, thus providing new experimental input for microscopic theories of strongly correlated fermions.

Interesting properties of ferroelectric Pb(Zr0.5Ti0.5)O3 nanotube array embedded in matrix medium

NASA Astrophysics Data System (ADS)

Adhikari, Rajendra; Fu, Huaxiang

2013-07-01

Finite-temperature first-principles based simulations are used to determine the structural and polarization properties of ferroelectric Pb(Zr0.5Ti0.5)O3 (PZT) nanotube array embedded in matrix medium of different ferroelectric strengths. Various interesting properties are found, including (i) that the system can behave either 3D-like, or 2D-like, or 1D-like; and (ii) the existence of an unusual structural phase in which 180° stripe domain coexists with vortex. Furthermore, we show in PZT tube array that a vortex phase can spontaneously transform into a ferroelectric phase of polarization by temperature alone, without applying external electric fields. Microscopic insights for understanding these properties are provided.

Engineering of many-body Majorana states in a topological insulator/s-wave superconductor heterostructure.

PubMed

Hung, Hsiang-Hsuan; Wu, Jiansheng; Sun, Kuei; Chiu, Ching-Kai

2017-06-14

We study a vortex chain in a thin film of a topological insulator with proximity-induced superconductivity-a promising platform to realize Majorana zero modes (MZMs)-by modeling it as a two-leg Majorana ladder. While each pair of MZMs hybridizes through vortex tunneling, we hereby show that MZMs can be stabilized on the ends of the ladder with the presence of tilted external magnetic field and four-Majorana interaction. Furthermore, a fruitful phase diagram is obtained by controlling the direction of magnetic field and the thickness of the sample. We reveal many-body Majorana states and interaction-induced topological phase transitions and also identify trivial-superconducting and commensurate/incommensurate charge-density-wave states in the phase diagram.

Interaction of N-vortex structures in a continuum, including atmosphere, hydrosphere and plasma

NASA Astrophysics Data System (ADS)

Belashov, Vasily Yu.

2017-10-01

The results of analysis and numerical simulation of evolution and interaction of the N-vortex structures of various configuration and different vorticities in the continuum including atmosphere, hydrosphere and plasma are presented. It is found that in dependence on initial conditions the regimes of weak interaction with quasi-stationary evolution and active interaction with the "phase intermixing", when the evolution can lead to formation of complex forms of vorticity regions, are realized in the N-vortex systems. For the 2-vortex interaction the generalized critical parameter determining qualitative character of interaction of vortices is introduced. It is shown that for given initial conditions its value divides modes of active interaction and quasi-stationary evolution. The results of simulation of evolution and interaction of the two-dimensional and three-dimensional vortex structures, including such phenomena as dynamics of the atmospheric synoptic vortices of cyclonic types and tornado, hydrodynamic 4-vortex interaction and also interaction in the systems of a type of "hydrodynamic vortex - dust particles" are presented. The applications of undertaken approach to the problems of such plasma systems as streams of charged particles in a uniform magnetic field B and plasma clouds in the ionosphere are considered. It is shown that the results obtained have obvious applications in studies of the dynamics of the vortex structures dynamics in atmosphere, hydrosphere and plasma.

PREFACE: Special section on vortex rings Special section on vortex rings

NASA Astrophysics Data System (ADS)

Fukumoto, Yasuhide

2009-10-01

This special section of Fluid Dynamics Research includes five articles on vortex rings in both classical and quantum fluids. The leading scientists of the field describe the trends in and the state-of-the-art development of experiments, theories and numerical simulations of vortex rings. The year 2008 was the 150th anniversary of 'vortex motion' since Hermann von Helmholtz opened up this field. In 1858, Helmholtz published a paper in Crelle's Journal which put forward the concept of 'vorticity' and made the first analysis of vortex motion. Fluid mechanics before that was limited to irrotational motion. In the absence of vorticity, the motion of an incompressible homogeneous fluid is virtually equivalent to a rigid-body motion in the sense that the fluid motion is determined once the boundary configuration is specified. Helmholtz proved, among other things, that, without viscosity, a vortex line is frozen into the fluid. This Helmholtz's law immediately implies the preservation of knots and links of vortex lines and its implication is enormous. One of the major trends of fluid mechanics since the latter half of the 20th century is to clarify the topological meaning of Helmholtz's law and to exploit it to develop theoretical and numerical methods to find the solutions of the Euler equations and to develop experimental techniques to gain an insight into fluid motion. Vortex rings are prominent coherent structures in a variety of fluid motions from the microscopic scale, through human and mesoscale to astrophysical scales, and have attracted people's interest. The late professor Philip G Saffman (1981) emphasized the significance of studies on vortex rings. One particular motion exemplifies the whole range of problems of vortex motion and is also a commonly known phenomenon, namely the vortex ring or smoke ring. Vortex rings are easily produced by dropping drops of one liquid into another, or by puffing fluid out of a hole, or by exhaling smoke if one has the skill. Their formation is a problem of vortex sheet dynamics, the steady state is a problem of existence, their duration is a problem of stability, and if there are several we have the problem of vortex interactions. Helmholtz himself, in the same paper (1858), devoted a few pages to an analysis of the motion of a vortex ring, and made substantial contributions. Since then, theoretical, experimental and numerical treatments of vortex rings have been developing continuously, yet we encounter mysteries and novel phenomena, with which vortex rings find new applications in, say, bio-fluid mechanics. Recently vortex rings have enlarged their scope beyond classical fluids to encompass super-fluids and Bose-Einstein condensates. On the occasion of the 150th anniversary of Helmholtz's theory on a vortex ring, it is worthwhile to bring together, in one issue, the latest understandings of and open problems in vortex rings from various aspects. The topics in this issue include development of theories and experiments for motion of vortex rings and their interaction with other vortex rings, flows and boundaries, with application to vortex-ring manipulation for flow control, original experiments on collision of vortex rings with a porous boundary, a novel numerical technique to simulate three-dimensional motion of vortex rings and new theories of dynamics of quantum vortex rings governed by nonlinear Schrödinger equations. I hope that this special section gives a sketch, in some proportion, of the current frontier of the field and provides a means to tackle future problems. References Saffman P G 1981 Dynamics of vorticity J. Fluid Mech. 106 49-58 von Helmholtz H 1858 Über Integrale der hydrodynamischen Gleichungen welche den Wirbelbewegungen entsprechen J. Reine Angew. Math. 55 25-55 (Engl. transl.: Tait P G 1867 On the integrals of the hydrodynamical equations which express vortex-motion Phil. Mag. 33 (4) 485-512)

Radiative effects of ozone waves on the Northern Hemisphere polar vortex and its modulation by the QBO

NASA Astrophysics Data System (ADS)

Silverman, Vered; Harnik, Nili; Matthes, Katja; Lubis, Sandro W.; Wahl, Sebastian

2018-05-01

The radiative effects induced by the zonally asymmetric part of the ozone field have been shown to significantly change the temperature of the NH winter polar cap, and correspondingly the strength of the polar vortex. In this paper, we aim to understand the physical processes behind these effects using the National Center for Atmospheric Research (NCAR)'s Whole Atmosphere Community Climate Model, run with 1960s ozone-depleting substances and greenhouse gases. We find a mid-winter polar vortex influence only when considering the quasi-biennial oscillation (QBO) phases separately, since ozone waves affect the vortex in an opposite manner. Specifically, the emergence of a midlatitude QBO signal is delayed by 1-2 months when radiative ozone-wave effects are removed. The influence of ozone waves on the winter polar vortex, via their modulation of shortwave heating, is not obvious, given that shortwave heating is largest during fall, when planetary stratospheric waves are weakest. Using a novel diagnostic of wave 1 temperature amplitude tendencies and a synoptic analysis of upward planetary wave pulses, we are able to show the chain of events that lead from a direct radiative effect on weak early fall upward-propagating planetary waves to a winter polar vortex modulation. We show that an important stage of this amplification is the modulation of individual wave life cycles, which accumulate during fall and early winter, before being amplified by wave-mean flow feedbacks. We find that the evolution of these early winter upward planetary wave pulses and their induced stratospheric zonal mean flow deceleration is qualitatively different between QBO phases, providing a new mechanistic view of the extratropical QBO signal. We further show how these differences result in opposite radiative ozone-wave effects between east and west QBOs.

Characterization of a Hybrid Optical Microscopy/Laser Ablation Liquid Vortex Capture/Electrospray Ionization System for Mass Spectrometry Imaging

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

Cahill, John F.; Kertesz, Vilmos; Van Berkel, Gary J.

Herein, a commercial optical microscope, laser microdissection instrument was coupled with an electrospray ionization mass spectrometer via a low profile liquid vortex capture probe to yield a hybrid optical microscopy/mass spectrometry imaging system. The instrument has bright-field and fluorescence microscopy capabilities in addition to a highly focused UV laser beam that is utilized for laser ablation of samples. With this system, material laser ablated from a sample using the microscope was caught by a liquid vortex capture probe and transported in solution for analysis by electrospray ionization mass spectrometry. Both lane scanning and spot sampling mass spectral imaging modes weremore » used. The smallest area the system was able to ablate was ~0.544 μm × ~0.544 μm, achieved by oversampling of the smallest laser ablation spot size that could be obtained (~1.9 μm). With use of a model photoresist surface, known features as small as ~1.5 μm were resolved. The capabilities of the system with real world samples were demonstrated first with a blended polymer thin film containing poly(2-vinylpyridine) and poly(N-vinylcarbazole). Using spot sampling imaging, sub-micrometer sized features (0.62, 0.86, and 0.98 μm) visible by optical microscopy were clearly distinguished in the mass spectral images. A second real world example showed the imaging of trace amounts of cocaine in mouse brain thin tissue sections. Lastly, with use of a lane scanning mode with ~6 μm × ~6 μm data pixels, features in the tissue as small as 15 μm in size could be distinguished in both the mass spectral and optical images.« less

Characterization of a Hybrid Optical Microscopy/Laser Ablation Liquid Vortex Capture/Electrospray Ionization System for Mass Spectrometry Imaging

DOE PAGES

Cahill, John F.; Kertesz, Vilmos; Van Berkel, Gary J.

2015-10-22

Herein, a commercial optical microscope, laser microdissection instrument was coupled with an electrospray ionization mass spectrometer via a low profile liquid vortex capture probe to yield a hybrid optical microscopy/mass spectrometry imaging system. The instrument has bright-field and fluorescence microscopy capabilities in addition to a highly focused UV laser beam that is utilized for laser ablation of samples. With this system, material laser ablated from a sample using the microscope was caught by a liquid vortex capture probe and transported in solution for analysis by electrospray ionization mass spectrometry. Both lane scanning and spot sampling mass spectral imaging modes weremore » used. The smallest area the system was able to ablate was ~0.544 μm × ~0.544 μm, achieved by oversampling of the smallest laser ablation spot size that could be obtained (~1.9 μm). With use of a model photoresist surface, known features as small as ~1.5 μm were resolved. The capabilities of the system with real world samples were demonstrated first with a blended polymer thin film containing poly(2-vinylpyridine) and poly(N-vinylcarbazole). Using spot sampling imaging, sub-micrometer sized features (0.62, 0.86, and 0.98 μm) visible by optical microscopy were clearly distinguished in the mass spectral images. A second real world example showed the imaging of trace amounts of cocaine in mouse brain thin tissue sections. Lastly, with use of a lane scanning mode with ~6 μm × ~6 μm data pixels, features in the tissue as small as 15 μm in size could be distinguished in both the mass spectral and optical images.« less

Plasma Shield for In-Air and Under-Water Beam Processes

NASA Astrophysics Data System (ADS)

Hershcovitch, Ady

2007-11-01

As the name suggests, the Plasma Shield is designed to chemically and thermally shield a target object by engulfing an area subjected to beam treatment with inert plasma. The shield consists of a vortex-stabilized arc that is employed to shield beams and workpiece area of interaction from atmospheric or liquid environment. A vortex-stabilized arc is established between a beam generating device (laser, ion or electron gun) and the target object. The arc, which is composed of a pure noble gas (chemically inert), engulfs the interaction region and shields it from any surrounding liquids like water or reactive gases. The vortex is composed of a sacrificial gas or liquid that swirls around and stabilizes the arc. In current art, many industrial processes like ion material modification by ion implantation, dry etching, and micro-fabrication, as well as, electron beam processing, like electron beam machining and electron beam melting is performed exclusively in vacuum, since electron guns, ion guns, their extractors and accelerators must be kept at a reasonably high vacuum, and since chemical interactions with atmospheric gases adversely affect numerous processes. Various processes involving electron ion and laser beams can, with the Plasma Shield be performed in practically any environment. For example, electron beam and laser welding can be performed under water, as well as, in situ repair of ship and nuclear reactor components. The plasma shield results in both thermal (since the plasma is hotter than the environment) and chemical shielding. The latter feature brings about in-vacuum process purity out of vacuum, and the thermal shielding aspect results in higher production rates. Recently plasma shielded electron beam welding experiments were performed resulting in the expected high quality in-air electron beam welding. Principle of operation and experimental results are to be discussed.

Flow structure of vortex-wing interaction

NASA Astrophysics Data System (ADS)

McKenna, Christopher K.

Impingement of a streamwise-oriented vortex upon a fin, tail, blade or wing represents a fundamental class of flow-structure interaction that extends across a range of applications. This interaction can give rise to time-averaged loading, as well as unsteady loading known as buffeting. The loading is sensitive to parameters of the incident vortex as well as the location of vortex impingement on the downstream aerodynamic surface, generically designated as a wing. Particle image velocimetry is employed to determine patterns of velocity, vorticity, swirl ratio, and streamlines on successive cross-flow planes upstream of and along the wing, which lead to volume representations and thereby characterization of the interaction. At locations upstream of the leading edge of the wing, the evolution of the incident vortex is affected by the presence of the wing, and is highly dependent on the spanwise location of vortex impingement. Even at spanwise locations of impingement well outboard of the wing tip, a substantial influence on the structure of the incident vortex at locations significantly upstream of the leading edge of the wing was observed. For spanwise locations close to or intersecting the vortex core, the effects of upstream influence of the wing on the vortex are to: decrease the swirl ratio; increase the streamwise velocity deficit; decrease the streamwise vorticity; increase the azimuthal vorticity; increase the upwash; decrease the downwash; and increase the root-mean-square fluctuations of both streamwise velocity and vorticity. The interrelationship between these effects is addressed, including the rapid attenuation of axial vorticity in presence of an enhanced defect of axial velocity in the central region of the vortex. Moreover, when the incident vortex is aligned with, or inboard of, the tip of the wing, the swirl ratio decreases to values associated with instability of the vortex, giving rise to enhanced values of azimuthal vorticity relative to the streamwise (axial) vorticity, as well as relatively large root-mean-square values of streamwise velocity and vorticity. Along the chord of the wing, the vortex interaction gives rise to distinct modes, which may involve either enhancement or suppression of the vortex generated at the tip of the wing. These modes are classified and interpreted in conjunction with computed modes at the Air Force Research Laboratory. Occurrence of a given mode of interaction is predominantly determined by the dimensionless location of the incident vortex relative to the tip of the wing and is generally insensitive to the Reynolds number and dimensionless circulation of the incident vortex. The genesis of the basic modes of interaction is clarified using streamline topology with associated critical points. Whereas formation of an enhanced tip vortex involves a region of large upwash in conjunction with localized flow separation, complete suppression of the tip vortex is associated with a small-scale separation-attachment bubble bounded by downwash at the wing tip. Oscillation of the wing at an amplitude and velocity nearly two orders of magnitude smaller than the wing chord and free stream velocity respectively can give rise to distinctive patterns of upwash, downwash, and shed vorticity, which are dependent on the outboard displacement of the incident vortex relative to the wing tip. Moreover, these patterns are a strong function of the phase of the wing motion during its oscillation cycle. At a given value of phase, the wing oscillation induces upwash that is reinforced by the upwash of the incident vortex, giving a maximum value of net upwash. Conversely, when these two origins of upwash counteract, rather than reinforce, one another during the oscillation cycle, the net upwash has its minimum value. Analogous interpretations hold for regions of maximum and minimum net downwash located outboard of the regions of upwash. During the oscillation cycle of the wing, the magnitude and scale of the vorticity shed from the tip of the wing are directly correlated with the net upwash, which takes different forms related to the outboard displacement of the incident vortex. As the location of the incident vortex is displaced towards the wing tip, both the maximum upwash and the maximum vorticity of the tip vortex initially increase, then decrease. For the limiting case where the incident vortex impinges directly upon the tip of the wing, there is no tip vortex or induced region of upwash. Furthermore, at small values of vortex displacement from the wing tip, the position of the incident vortex varies significantly from its nominal position during the oscillation cycle. For all locations of the incident vortex, it is shown that, despite the small amplitude of the wing motion, the flow topology is fundamentally different at maximum positive and negative values of the wing velocity, that is, they are not symmetric.

β-CD/ATP composite materials for use in dispersive solid-phase extraction to measure (fluoro)quinolone antibiotics in honey samples.

PubMed

Cui, Xiangqian; Zhang, Panjie; Yang, Xiaoling; Yang, Miyi; Zhou, Wenfeng; Zhang, Sanbin; Gao, Haixiang; Lu, Runhua

2015-06-09

A novel sorbent (β-CD/ATP composite) for dispersive solid-phase extraction (d-SPE) prepared by bonding β-cyclodextrin to modified attapulgite via silane coupling was used to determine the concentrations of four (fluoro)quinolones (Qs) in honey samples. The subsequent quantification of the Qs (ciprofloxacin, norfloxacin, ofloxacin, and gatifloxacin) was accomplished using high-performance liquid chromatography (HPLC) with ultraviolet detection after the d-SPE procedure. Parameters that may influence the extraction efficiency, such as type and volume of the eluent, type and amount of the sorbent, times of the vortex and sonication process, and pH of the sample, were investigated using batch and column procedures. The optimal experimental conditions (5 mL sample at pH 3, 4 mg of β-CD/ATP composite as the sorbent, 200 μL of 40% ammonia in methanol as the eluent, with vortex time 60s and sonication time 6 min, and no addition of salt) were obtained from this statistical evaluation. The limits of detection (LODs) were determined to the range from 0.30 to 3.95 μg L(-1). Good recoveries (83.6-88.6%) were obtained under the optimum conditions, and the relative standard deviations (RSDs), which are used to indicate reproducibility, were less than 7.4%. The method was validated with three real honey samples, and the results demonstrated that β-CD/ATP composite possessed a high adsorption capacity for Qs. Although the LODs were slightly higher than expected, this study confirmed the possibility of using cyclodextrin grafted palygorskite in analytical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Helical solutions of the bidirectional vortex in a cylindrical cyclone: Beltramian and Trkalian motions

NASA Astrophysics Data System (ADS)

Majdalani, Joseph

2012-10-01

In this work, two families of helical motions are investigated as prospective candidates for describing the bidirectional vortex field in a right-cylindrical chamber. These basic solutions are relevant to cyclone separators and to idealized representations of vortex-fired liquid and hybrid rocket engines in which bidirectional vortex motion is established. To begin, the bulk fluid motion is taken to be isentropic along streamlines, with no concern for reactions, heat transfer, viscosity, compressibility or unsteadiness. Then using the Bragg-Hawthorne equation for steady, inviscid, axisymmetric motion, two families of Euler solutions are derived. Among the characteristics of the newly developed solutions one may note the axial dependence of the swirl velocity, the Trkalian and Beltramian types of the helical motions, the sensitivity of the solutions to the outlet radius, the alternate locations of the mantle, and the increased axial and radial velocity magnitudes, including the rate of mass transfer across the mantle, for which explicit approximations are obtained. Our results are compared to an existing, complex lamellar model of the bidirectional vortex in which the swirl velocity reduces to a free vortex. In this vein, we find the strictly Beltramian flows to share virtually identical pressure variations and radial pressure gradients with those associated with the complex lamellar motion. Furthermore, both families warrant an asymptotic treatment to overcome their endpoint limitations caused by their omission of viscous stresses. From a broader perspective, the work delineates a logical framework through which self-similar, axisymmetric solutions to bidirectional and multidirectional vortex motions may be pursued. It also illustrates the manner through which different formulations may be arrived at depending on the types of wall boundary conditions. For example, both the slip condition at the sidewall and the inlet flow pattern at the headwall may be enforced or relaxed.

Doppler radar detection of vortex hazard indicators

NASA Technical Reports Server (NTRS)

Nespor, Jerald D.; Hudson, B.; Stegall, R. L.; Freedman, Jerome E.

1994-01-01

Wake vortex experiments were conducted at White Sands Missile Range, NM using the AN/MPS-39 Multiple Object Tracking Radar (MOTR). The purpose of these experiments was twofold. The first objective was to verify that radar returns from wake vortex are observed for some time after the passage of an aircraft. The second objective was to verify that other vortex hazard indicators such as ambient wind speed and direction could also be detected. The present study addresses the Doppler characteristics of wake vortex and clear air returns based upon measurements employing MOTR, a very sensitive C-Band phased array radar. In this regard, the experiment was conducted so that the spectral characteristics could be determined on a dwell to-dwell basis. Results are presented from measurements of the backscattered power (equivalent structure constant), radial velocity and spectral width when the aircraft flies transverse and axial to the radar beam. The statistics of the backscattered power and spectral width for each case are given. In addition, the scan strategy, experimental test procedure and radar parameters are presented.

Frequency spirals

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

Ottino-Löffler, Bertrand; Strogatz, Steven H., E-mail: strogatz@cornell.edu

2016-09-15

We study the dynamics of coupled phase oscillators on a two-dimensional Kuramoto lattice with periodic boundary conditions. For coupling strengths just below the transition to global phase-locking, we find localized spatiotemporal patterns that we call “frequency spirals.” These patterns cannot be seen under time averaging; they become visible only when we examine the spatial variation of the oscillators' instantaneous frequencies, where they manifest themselves as two-armed rotating spirals. In the more familiar phase representation, they appear as wobbly periodic patterns surrounding a phase vortex. Unlike the stationary phase vortices seen in magnetic spin systems, or the rotating spiral waves seenmore » in reaction-diffusion systems, frequency spirals librate: the phases of the oscillators surrounding the central vortex move forward and then backward, executing a periodic motion with zero winding number. We construct the simplest frequency spiral and characterize its properties using analytical and numerical methods. Simulations show that frequency spirals in large lattices behave much like this simple prototype.« less

Theory and applications of free-electron vortex states

NASA Astrophysics Data System (ADS)

Bliokh, K. Y.; Ivanov, I. P.; Guzzinati, G.; Clark, L.; Van Boxem, R.; Béché, A.; Juchtmans, R.; Alonso, M. A.; Schattschneider, P.; Nori, F.; Verbeeck, J.

2017-05-01

Both classical and quantum waves can form vortices : entities with helical phase fronts and circulating current densities. These features determine the intrinsic orbital angular momentum carried by localized vortex states. In the past 25 years, optical vortex beams have become an inherent part of modern optics, with many remarkable achievements and applications. In the past decade, it has been realized and demonstrated that such vortex beams or wavepackets can also appear in free electron waves, in particular, in electron microscopy. Interest in free-electron vortex states quickly spread over different areas of physics: from basic aspects of quantum mechanics, via applications for fine probing of matter (including individual atoms), to high-energy particle collision and radiation processes. Here we provide a comprehensive review of theoretical and experimental studies in this emerging field of research. We describe the main properties of electron vortex states, experimental achievements and possible applications within transmission electron microscopy, as well as the possible role of vortex electrons in relativistic and high-energy processes. We aim to provide a balanced description including a pedagogical introduction, solid theoretical basis, and a wide range of practical details. Special attention is paid to translating theoretical insights into suggestions for future experiments, in electron microscopy and beyond, in any situation where free electrons occur.

Induced Moment Effects of Formation Flight Using Two F/A-18 Aircraft

NASA Technical Reports Server (NTRS)

Hansen, Jennifer L.; Cobleigh, Brent R.

2002-01-01

Previous investigations into formation flight have shown the possibility for significant fuel savings through drag reduction. Using two F/A-18 aircraft, NASA Dryden Flight Research Center has investigated flying aircraft in autonomous formation. Positioning the trailing airplane for best drag reduction requires investigation of the wingtip vortex effects induced by the leading airplane. A full accounting of the vortex effect on the trailing airplane is desired to validate vortex-effect prediction methods and provide a database for the design of a formation flight autopilot. A recent flight phase has mapped the complete wingtip vortex effects at two flight conditions with the trailing airplane at varying distances behind the leading one. Force and moment data at Mach 0.56 and an altitude of 25,000 ft and Mach 0.86 and an altitude of 36,000 ft have been obtained with 20, 55, 110, and 190 ft of longitudinal distance between the aircraft. The moments induced by the vortex on the trailing airplane were well within the pilot's ability to control. This report discusses the data analysis methods and vortex-induced effects on moments and side force. An assessment of the impact of the nonlinear vortex effects on the design of a formation autopilot is offered.

Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates

PubMed Central

Yang, Tao; Hu, Zhi-Qiang; Zou, Shan; Liu, Wu-Ming

2016-01-01

Dynamics of vortex clusters is essential for understanding diverse superfluid phenomena. In this paper, we examine the dynamics of vortex quadrupoles in a trapped two-dimensional (2D) Bose-Einstein condensate. We find that the movement of these vortex-clusters fall into three distinct regimes which are fully described by the radial positions of the vortices in a 2D isotropic harmonic trap, or by the major radius (minor radius) of the elliptical equipotential lines decided by the vortex positions in a 2D anisotropic harmonic trap. In the “recombination” and “exchange” regimes the quadrupole structure maintains, while the vortices annihilate each other permanently in the “annihilation” regime. We find that the mechanism of the charge flipping in the “exchange” regime and the disappearance of the quadrupole structure in the “annihilation” regime are both through an intermediate state where two vortex dipoles connected through a soliton ring. We give the parameter ranges for these three regimes in coordinate space for a specific initial configuration and phase diagram of the vortex positions with respect to the Thomas-Fermi radius of the condensate. We show that the results are also applicable to systems with quantum fluctuations for the short-time evolution. PMID:27464981

Liquid-liquid microextraction of synthetic pigments in beverages using a hydrophobic deep eutectic solvent.

PubMed

Zhu, Shuqiang; Zhou, Jia; Jia, Hongfang; Zhang, Haixia

2018-03-15

A method was developed for the determination of eight synthetic pigments in beverage samples by liquid-liquid microextraction followed by high performance liquid chromatography. Using hydrophobic deep eutectic solvent (DES) as the microextraction solvent, several key parameters were optimized, including the type and volume of the hydrophobic DES, pH value, vortex time and salt content. Detection limits were in the range 0.016-1.12 ng/mL, recoveries were in the range 74.5-102.5% and relative standard deviations were <5.4%. The method is simple, green and practical, and could be applied to the extraction and determination of synthetic pigments in beverages. Copyright © 2017 Elsevier Ltd. All rights reserved.

A numerical simulation of the dispersal of aerial sprays

NASA Technical Reports Server (NTRS)

Bragg, M. B.

1981-01-01

A computer program was developed to predict the trajectory, ground deposition, and drift of liquid sprays injected into the wake of an agricultural aircraft in ground effect. The program uses a horseshoe vortex wake model and includes the effects of liquid droplet evaporation, crosswind, the propeller slipstream, ground effect, and tunnel walls on small scale models. This user's guide includes several case examples demonstrating user options. A complete listing of the FORTRAN program is provided.

Determination of Levetiracetam in Human Plasma by Dispersive Liquid-Liquid Microextraction Followed by Gas Chromatography-Mass Spectrometry

PubMed Central

2016-01-01

Levetiracetam (LEV) is an antiepileptic drug that is clinically effective in generalized and partial epilepsy syndromes. The use of this drug has been increasing in clinical practice and intra- or -interindividual variability has been exhibited for special population. For this reason, bioanalytical methods are required for drug monitoring in biological matrices. So this work presents a dispersive liquid-liquid microextraction method followed by gas chromatography-mass spectrometry (DLLME-GC-MS) for LEV quantification in human plasma. However, due to the matrix complexity a previous purification step is required. Unlike other pretreatment techniques presented in the literature, for the first time, a procedure employing ultrafiltration tubes Amicon® (10 kDa porous size) without organic solvent consumption was developed. GC-MS analyses were carried out using a linear temperature program, capillary fused silica column, and helium as the carrier gas. DLLME optimized parameters were type and volume of extraction and dispersing solvents, salt addition, and vortex agitation time. Under chosen parameters (extraction solvent: chloroform, 130 μL; dispersing solvent: isopropyl alcohol, 400 μL; no salt addition and no vortex agitation time), the method was completely validated and all parameters were in agreement with the literature recommendations. LEV was quantified in patient's plasma sample using less than 550 μL of organic solvent. PMID:27830105

Experimental and Computational Study of Trapped Vortex Combustor Sector Rig with Tri-pass Diffuser

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Shouse, D. T.; Roquemore, W. M.; Burrus, D. L.; Duncan, B. S.; Ryder, R. C.; Brankovic, A.; Liu, N.-S.; Gallagher, J. R.; Hendricks, J. A.

2001-01-01

The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL (Rich burn/Quick mix/Lean burn) modes of combustion. The present work describes the operational principles of the TVC, and provides detailed performance data on a configuration featuring a tri-pass diffusion system. Performance data include EINOx (NO(sub x) emission index) results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable in comparison to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.

Emission of discrete vortex rings by a vibrating grid in superfluid 3He-B: a precursor to quantum turbulence.

PubMed

Bradley, D I; Clubb, D O; Fisher, S N; Guénault, A M; Haley, R P; Matthews, C J; Pickett, G R; Tsepelin, V; Zaki, K

2005-07-15

We report a transition in the vorticity generated by a grid moving in the B phase of superfluid 3He at T

Topological transformation of fractional optical vortex beams using computer generated holograms

NASA Astrophysics Data System (ADS)

Maji, Satyajit; Brundavanam, Maruthi M.

2018-04-01

Optical vortex beams with fractional topological charges (TCs) are generated by the diffraction of a Gaussian beam using computer generated holograms embedded with mixed screw-edge dislocations. When the input Gaussian beam has a finite wave-front curvature, the generated fractional vortex beams show distinct topological transformations in comparison to the integer charge optical vortices. The topological transformations at different fractional TCs are investigated through the birth and evolution of the points of phase singularity, the azimuthal momentum transformation, occurrence of critical points in the transverse momentum and the vorticity around the singular points. This study is helpful to achieve better control in optical micro-manipulation applications.

Electroelastic fields in artificially created vortex cores in epitaxial BiFeO 3 thin films

DOE PAGES

Winchester, Ben; Wisinger, Nina Balke; Cheng, X. X.; ...

2015-08-03

Here we employ phase-field modeling to explore the elastic properties of artificially created 1-D domain walls in (001) p-oriented BiFeO 3 thin films, composed of a junction of the four polarization variants, all with the same out-of-plane polarization. It was found that these junctions exhibit peculiarly high electroelastic fields induced by the neighboring ferroelastic/ferroelectric domains. The vortex core exhibits a volume expansion, while the anti-vortex core is more compressive. We also discuss possible ways to control the electroelastic field, such as varying material constant and applying transverse electric field.

Dynamic mode decomposition of separated flow over a finite blunt plate: time-resolved particle image velocimetry measurements

NASA Astrophysics Data System (ADS)

Liu, Yingzheng; Zhang, Qingshan

2015-07-01

Dynamic mode decomposition (DMD) analysis was performed on a large number of realizations of the separated flow around a finite blunt plate, which were determined by using planar time-resolved particle image velocimetry (TR-PIV). Three plates with different chord-to-thickness ratios corresponding to globally different flow patterns were particularly selected for comparison: L/D = 3.0, 6.0 and 9.0. The main attention was placed on dynamic variations in the dominant events and their interactive influences on the global fluid flow in terms of the DMD analysis. Toward this end, a real-time data transfer from the high-speed camera to the arrayed disks was built to enable continuous sampling of the spatiotemporally varying flows at the frequency of 250 Hz for a long run. The spectra of the wall-normal velocity fluctuation, the energy spectra of the DMD modes, and their spatial patterns convincingly determined the energetic unsteady events, i.e., St = 0.051 (Karman vortex street), 0.109 (harmonic event of Karman vortex street) and 0.197 (leading-edge vortex) in the shortest system L/D = 3.0, St = 0.159 (Karman vortex street) and 0.242 (leading-edge vortex) in the system L/D = 6.0, and St = 0.156 (Karman vortex street) and 0.241 (leading-edge vortex) in the longest system L/D = 9.0. In the shortest system L/D = 3.0, the first DMD mode pattern demonstrated intensified entrainment of the massive fluid above and below the whole plate by the Karman vortex street. The phase-dependent variation in the low-order flow field elucidated that this motion was sustained by the consecutive mechanisms of the convective leading-edge vortices near the upper and lower trailing edges, and the large-scale vortical structures occurring immediately behind the trailing edge, whereas the leading-edge vortices were entrained and decayed into the near wake. For the system L/D = 6.0, the closely approximated energy spectra at St = 0.159 and 0.242 indicated the balanced dominance of dual unsteady events in the measurement region. The Karman vortex street was found to induce considerable localized movement of the fluid near the trailing edges of the plate. However, the leading-edge vortices near the trailing edge were found to detach away from the plate and fully decay around 0.5 D behind the trailing edge, where a well-ordered origination of the downstream large-scale vortical structures (the Karman vortex street) was established and might be locally energized by the decayed leading-edge vortex. In the longest system L/D = 9.0, the phase-dependent variations in the low-order flow disclosed a rapid decay of the leading-edge vortices beyond the reattachment zone, reaching the fully diffused state near the trailing edges. Accordingly, no clear signature of the interaction between the Karman vortex street and the leading-edge vortex could be found in the dynamic process of the leading-edge vortex.

Optical Rogue Waves in Vortex Turbulence.

PubMed

Gibson, Christopher J; Yao, Alison M; Oppo, Gian-Luca

2016-01-29

We present a spatiotemporal mechanism for producing 2D optical rogue waves in the presence of a turbulent state with creation, interaction, and annihilation of optical vortices. Spatially periodic structures with bound phase lose stability to phase unbound turbulent states in complex Ginzburg-Landau and Swift-Hohenberg models with external driving. When the pumping is high and the external driving is low, synchronized oscillations are unstable and lead to spatiotemporal vortex-mediated turbulence with high excursions in amplitude. Nonlinear amplification leads to rogue waves close to turbulent optical vortices, where the amplitude tends to zero, and to probability density functions (PDFs) with long tails typical of extreme optical events.

Force Generation by Flapping Foils

NASA Astrophysics Data System (ADS)

Bandyopadhyay, P. R.; Donnelly, M.

1996-11-01

Aquatic animals like fish use flapping caudal fins to produce axial and cross-stream forces. During WW2, German scientists had built and tested an underwater vehicle powered by similar flapping foils. We have examined the forces produced by a pair of flapping foils. We have examined the forced produced by a pair of flapping foils attached to the tail end of a small axisymmetric cylinder. The foils operate in-phase (called waving), or in anti-phase (called clapping). In a low-speed water tunnel, we have undertaken time-dependent measurements of axial and cross-stream forces and moments that are exerted by the vortex shedding process over the entire body. Phase-matched LDV measurements of vorticity-velocity vectors, as well as limited flow visualization of the periodic vortex shedding process have also been carried out. The direction of the induced velocity within a pair of shed vortices determines the nature of the forces produced, viz., thrust or drag or cross-stream forces. The clapping mode produces a widely dispersed symmetric array of vortices which results in axial forces only (thrust and rag). On the other hand, the vortex array is staggered in the waving mode and cross-stream (maneuvering) forces are then generated.

Characterizing cycle-to-cycle variations of the shedding cycle in the turbulent wake of a normal flat plate using generalized phase averages

NASA Astrophysics Data System (ADS)

Martinuzzi, Robert

2016-11-01

Quasi-periodic vortex shedding in the turbulent wake of a thin-flat plate placed normal to a uniform stream at Reynolds number of 6700 is investigated based on Particle Image Velocimetry experiments. The wake structure and vortex formation are characterized using a generalized phase average (GPA), a refinement of the triple decomposition of Reynolds and Hussain (1970) incorporating elements of mean-field theory (Stuart, 1958). The resulting analysis highlights the importance of cycle-to-cycle variations in characterizing vortex formation, wake topology and the residual turbulent Reynolds Stresses. For example, it is shown that during high-amplitude cycles vorticity is strongly concentrated within the well-organized shed vortices, whereas during low-amplitude cycles the shed vortices are highly distorted resulting in significant modulation of the shedding frequency. It is found that high-amplitude cycles contribute more to the coherent Reynolds stress field while the low-amplitude cycles contribute to the residual stress field. It is further shown that traditional phase-averaging techniques lead to an over-estimation of the residual stress field. Natural Sciences and Engineering Research Council of Canada.

Visualization of liquid-assisted hard tissue ablation with a pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Li, X. W.; Chen, C. G.; Zhang, X. Z.; Zhan, Z. L.; Xie, S. S.

2015-01-01

To investigate the characteristics of liquid-mediated hard tissue ablation induced by a pulsed CO2 laser with a wavelength of 10.6 μm, a high speed camera was used to monitor the interaction between water, tissue and laser irradiation. The results showed that laser irradiation can directly impact on tissue through a vapor channel formed by the leading part of the laser pulse. The ablation debris plays a key role in liquid-assisted laser ablation, having the ability to keep the vapor channel open to extend actuation time. The runoff effect induced by vortex convection liquid flow can remove the tissue that obstructs the effect of the next laser pulse.

Vortex dynamics in the wake of a pivoted cylinder undergoing vortex-induced vibrations with elliptic trajectories

NASA Astrophysics Data System (ADS)

Marble, Erik; Morton, Christopher; Yarusevych, Serhiy

2018-05-01

Vortex-induced vibrations of a pivoted cylinder are investigated experimentally at a fixed Reynolds number of 3100, a mass ratio of 10.8, and a range of reduced velocities, 4.42 ≤ U^* ≤ 9.05. For these conditions, the cylinder traces elliptic trajectories, with the experimental conditions producing three out of four possible combinations of orbiting direction and primary axis alignment relative to the incoming flow. The study focuses on the quantitative analysis of wake topology and its relation to this type of structural response. Velocity fields were measured using time-resolved, two-component particle image velocimetry (TR-PIV). These results show that phase-averaged wake topology generally agrees with the Morse and Williamson (J Fluids Struct 25(4):697-712, 2009) shedding map for one-degree-of-freedom vortex-induced vibrations, with 2S, 2{P}o, and 2P shedding patterns observed within the range of reduced velocities studied here. Vortex tracking and vortex strength quantification are used to analyze the vortex shedding process and how it relates to cylinder response. In the case of 2S vortex shedding, vortices are shed when the cylinder is approaching the maximum transverse displacement and reaches the streamwise equilibrium. 2P vortices are shed approximately half a period earlier in the cylinder's elliptic trajectory. Leading vortices shed immediately after the peak in transverse oscillation and trailing vortices shed near the equilibrium of transverse oscillation. The orientation and direction of the cylinder's elliptic trajectory are shown to influence the timing of vortex shedding, inducing changes in the 2P wake topology.

Transitions in the vortex wake behind the plunging profile

NASA Astrophysics Data System (ADS)

Kozłowski, Tomasz; Kudela, Henryk

2014-12-01

In this study we investigate numerically the vortex wake formation behind the profile performing simple harmonic motion known in the literature as plunging. This research was inspired by the flapping motion which is appropriate for birds, insects and fishes. We assume the two dimensional model of flow. Depending on the parameters such as plunging amplitude, frequency and the Reynolds number, we demonstrate many different types of vortex street behind the profile. It is well known that the type of vortex wake determines the hydrodynamic forces acting on the profile. Dependences of the plunging amplitude, the Strouhal number and various topology vortices are established by constructing the phase transition diagram. The areas in the diagram related to the drag, thrust, and lift force generation are captured. We notice also the areas where the vorticity field is disordered. The disordered vorticity field does not allow maintenance of the periodic forces on the profile. An increase in the Reynolds number leads to the transition of the vortex wake behind the profile. The transition is caused by the phenomenon of boundary layer eruption. Further increase of the Reynolds number causes the vortex street related to the generation of the lift force to vanish.

Effect of AFT Rotor on the Inter-Rotor Flow of an Open Rotor Propulsion System

NASA Technical Reports Server (NTRS)

Slaboch, Paul E.; Stephens, David B.; Van Zante, Dale E.

2016-01-01

The effects of the aft rotor on the inter-rotor flow field of an open rotor propulsion rig were examined. A Particle Image Velocimetry (PIV) dataset that was acquired phase locked to the front rotor position has been phase averaged based on the relative phase angle between the forward and aft rotors. The aft rotor phase was determined by feature tracking in raw PIV images through an image processing algorithm. The effect of the aft rotor potential field on the inter-rotor flow were analyzed and shown to be in good agreement with Computational Fluid Dynamics (CFD) simulations. It was shown that the aft rotor had no substantial effect on the position of the forward rotor tip vortex but did have a small effect on the circulation strength of the vortex when the rotors were highly loaded.

The effect of single-horn glaze ice on the vortex structures in the wake of a horizontal axis wind turbine

NASA Astrophysics Data System (ADS)

Jin, Zhe-Yan; Dong, Qiao-Tian; Yang, Zhi-Gang

2015-02-01

The present study experimentally investigated the effect of a simulated single-horn glaze ice accreted on rotor blades on the vortex structures in the wake of a horizontal axis wind turbine by using the stereoscopic particle image velocimetry (Stereo-PIV) technique. During the experiments, four horizontal axis wind turbine models were tested, and both "free-run" and "phase-locked" Stereo-PIV measurements were carried out. Based on the "free-run" measurements, it was found that because of the simulated single-horn glaze ice, the shape, vorticity, and trajectory of tip vortices were changed significantly, and less kinetic energy of the airflow could be harvested by the wind turbine. In addition, the "phase-locked" results indicated that the presence of simulated single-horn glaze ice resulted in a dramatic reduction of the vorticity peak of the tip vortices. Moreover, as the length of the glaze ice increased, both root and tip vortex gaps were found to increase accordingly.

Annular vortex merging processes in non-neutral electron plasmas

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

Kaga, Chikato, E-mail: d146073@hiroshima-u.ac.jp; Ito, Kiyokazu; Higaki, Hiroyuki

2015-06-29

Non-neutral electron plasmas in a uniform magnetic field are investigated experimentally as a two dimensional (2D) fluid. Previously, it was reported that 2D phase space volume increases during a vortex merging process with viscosity. However, the measurement was restricted to a plasma with a high density. Here, an alternative method is introduced to evaluate a similar process for a plasma with a low density.

Focusing properties of arbitrary optical fields combining spiral phase and cylindrically symmetric state of polarization.

PubMed

Man, Zhongsheng; Bai, Zhidong; Zhang, Shuoshuo; Li, Jinjian; Li, Xiaoyu; Ge, Xiaolu; Zhang, Yuquan; Fu, Shenggui

2018-06-01

The tight focusing properties of optical fields combining a spiral phase and cylindrically symmetric state of polarization are presented. First, we theoretically analyze the mathematical characterization, Stokes parameters, and Poincaré sphere representations of arbitrary cylindrical vector (CV) vortex beams. Then, based on the vector diffraction theory, we derive and build an integrated analytical model to calculate the electromagnetic field and Poynting vector distributions of the input CV vortex beams. The calculations reveal that a generalized CV vortex beam can generate a sharper focal spot than that of a radially polarized (RP) plane beam in the focal plane. Besides, the focal size decrease accompanies its elongation along the optical axis. Hence, it seems that there is a trade-off between the transverse and axial resolutions. In addition, under the precondition that the absolute values between polarization order and topological charge are equal, a higher-order CV vortex can also achieve a smaller focal size than an RP plane beam. Further, the intensity for the sidelobe admits a significant suppression. To give a deep understanding of the peculiar focusing properties, the magnetic field and Poynting vector distributions are also demonstrated in detail. These properties may be helpful in applications such as optical trapping and manipulation of particles and superresolution microscopy imaging.

Vortex pinning landscape in MOD-TFA YBCO nanostroctured films

NASA Astrophysics Data System (ADS)

Gutierrez, J.; Puig, T.; Pomar, A.; Obradors, X.

2008-03-01

A methodology of general validity to study vortex pinning in YBCO based on Jc transport measurements is described. It permits to identify, separate and quantify three basic vortex pinning contributions associated to anisotropic-strong, isotropic-strong and isotropic-weak pinning centers. Thereof, the corresponding vortex pinning phase diagrams are built up. This methodology is applied to the new solution-derived YBCO nanostructured films, including controlled interfacial pinning by the growth of nanostructured templates by means of self-assembled processes [1] and YBCO-BaZrO3 nanocomposites prepared by modified solution precursors. The application of the methodology and comparison with a standard solution-derived YBCO film [2], enables us to identify the nature and the effect of the additional pinning centers induced. The nanostructured templates films show c-axis pinning strongly increased, controlling most of the pinning phase diagram. On the other hand, the nanocomposites have achieved so far, the highest pinning properties in HTc-superconductors [3], being the isotropic-strong defects contribution the origin of their unique properties. [1] M. Gibert et al, Adv. Mat. vol 19, p. 3937 (2007) [2] Puig.T et al, SuST EUCAS 2007 (to be published) [3] J. Gutierrez et al, Nat. Mat. vol. 6, p. 367 (2007) * Work supported by HIPERCHEM, NANOARTIS and MAT2005-02047

Critical current density, vortex dynamics, and phase diagram of single-crystal FeSe

NASA Astrophysics Data System (ADS)

Sun, Yue; Pyon, Sunseng; Tamegai, Tsuyoshi; Kobayashi, Ryo; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

2015-10-01

We present a comprehensive study of the vortex pinning and dynamics in a high-quality FeSe single crystal which is free from doping-introduced inhomogeneities and charged quasiparticle scattering because of its innate superconductivity. The critical current density Jc is found to be almost isotropic and reaches a value of ˜3 ×104 A /cm2 at 2 K (self-field) for both H ∥c and a b . The normalized magnetic relaxation rate S (=∣d ln M /d ln t ∣ ) shows a temperature-insensitive plateau behavior in the intermediate temperature range with a relatively high creep rate (S ˜ 0.02 under zero field), which is interpreted in the framework of the collective creep theory. A crossover from the elastic to plastic creep is observed, while the fishtail effect is absent for both H ∥c and a b . Based on this observation, the origin of the fishtail effect is also discussed. Combining the results of Jc and S , the vortex motion in the FeSe single crystal is found to be dominated by sparse, strong pointlike pinning from nanometer-sized defects or imperfections. The weak collective pinning is also observed and proved in the form of large bundles. Besides, the vortex phase diagram of FeSe is also constructed and discussed.

Smart vortex generator transformed by change in ambient temperature and aerodynamic force

NASA Astrophysics Data System (ADS)

Ikeda, Tadashige; Masuda, Shinya; Ueda, Tetsuhiko

2007-04-01

A Smart Vortex Generator (SVG) concept has been proposed, where the SVG is autonomously transformed between an upright vortex-generating position in take-off and landing and a flat drag-reducing position in a cruise. This SVG is made of a Shape Memory Alloy (SMA), which is in the austenite phase and memorizes the upright position at high temperatures of the take-off and landing. At low temperatures during ascent the SVG is transformed into a martensite phase, and it lies flat against a base structure due to external or/and internal forces. In this paper, we examine whether the SVG can be transformed into the drag-reducing position by an aerodynamic force. To this end, numerical simulations are carried out with a simple line element model. The aerodynamic force applied on the SVG is calculated by a commercial CFD program. Result reveals that this SVG can be transformed from the upright vortex-generating position into the drag-reducing position by just an airplane climbing, and vice versa, if the SMA applied to the SVG has the two-way shape memory effect. If the SMA has the one-way shape memory effect, it is necessary to reduce the stiffness of the SVG or/and use a counter spring.

Climate model diversity in the Northern Hemisphere Polar vortex response to climate change.

NASA Astrophysics Data System (ADS)

Simpson, I.; Seager, R.; Hitchcock, P.; Cohen, N.

2017-12-01

Global climate models vary widely in their predictions of the future of the Northern Hemisphere stratospheric polar vortex, with some showing a significant strengthening of the vortex, some showing a significant weakening and others displaying a response that is not outside of the range expected from internal variability alone. This inter-model spread in stratospheric predictions may account for some inter-model spread in tropospheric predictions with important implications for the storm tracks and regional climate change, particularly for the North Atlantic sector. Here, our current state of understanding of this model spread and its tropospheric impacts will be reviewed. Previous studies have proposed relationships between a models polar vortex response to climate change and its present day vortex climatology while others have demonstrated links between a models polar vortex response and changing wave activity coming up from the troposphere below under a warming climate. The extent to which these mechanisms can account for the spread in polar vortex changes exhibited by the Coupled Model Intercomparison Project, phase 5 models will be assessed. In addition, preliminary results from a series of idealized experiments with the Community Atmosphere Model will be presented. In these experiments, nudging of the stratospheric zonal mean state has been imposed to mimic the inter-model spread in the polar vortex response to climate change so that the downward influence of the spread in zonal mean stratospheric responses on the tropospheric circulation can be assessed within one model.

Numerical Studies of Flow Past Two Side-by-Side Circular Cylinders

NASA Astrophysics Data System (ADS)

Shao, J.; Zhang, C.

Multiple circular cylindrical configurations are widely used in engineering applications. The fluid dynamics of the flow around two identical circular cylinders in side-by-side arrangement has been investigated by both experiments and numerical simulations. The center-to-center transverse pitch ratio T/D plays an important role in determining the flow features. It is observed that for 1 < T/D < 1.1 to 1.2, a single vortex street is formed; for 1.2< T/D < 2 to 2.2, bi-stable narrow and wide wakes are formed; for 2.7< T/D < 4 or 5, anti-phase or in-phase vortex streets are formed. In the current study, the vortex structures of turbulent flows past two slightly heated side-by-side circular cylinders are investigated employing the large eddy simulation (LES). Simulations are performed using a commercial CFD software, FLUENT. The Smagorinsky-Lilly subgrid-scale model is employed for the large eddy simulation. The Reynolds number based on free-stream velocity and cylinder diameter is 5 800, which is in the subcritical regime. The transverse pitch ratio T/D = 3 is investigated. Laminar boundary layer, transition in shear layer, flow separation, large vortex structures and flow interference in the wake are all involved in the flow. Such complex flow features make the current study a challenging task. Both flow field and temperature field are investigated. The calculated results are analyzed and compared with experimental data. The simulation results are qualitatively in accordance with experimental observations. Two anti-phase vortex streets are obtained by the large-eddy simulation, which agrees with the experimental observation. At this transverse pitch ratio, these two cylinders behave as independent, isolated single cylinder in cross flow. The time-averaged streamwise velocity and temperature at x/D=10 are in good agreement with the experimental data. Figure1 displays the instantaneous spanwise vorticity at the center plane.

[Determination of gossypol in edible vegetable oil with high performance liquid chromatography-tandem mass spectrometry].

PubMed

Zhang, Wenhua; Huang, Chaoqun; Xie, Wen; Shen, Li

2014-06-01

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of gossypol in edible vegetable oil. The sample was extracted with ethyl alcohol by vortex-excited oscillation. The extract was cleaned up by 0.22 microm filter membrane and centrifuged for 5 min at 4 000 r/min after standing in a fridge at 4 degrees C for 30 min. The compound was separated on a C18 column (100 mm x 2.1 mm, 3.5 microm) with acetonitrile and 1% (v/v) formic acid aqueous solution as mobile phase. The detection of gossypol was carried out by LC-MS/MS with positive electrospray ionization under multiple reaction monitoring (MRM) mode using external standard method. The limits of quantification (S/N > 10) of gossypol in edible vegetable oil was 1 mg/kg. The recoveries were from 87.4% to 100% at the spiked levels of 1, 2, 200 mg/kg of gossypol in edible vegetable oil with the relative standard deviations (RSDs) between 3.9% and 12.2%. The method, with high sensitivity, good precision and high recovery, was suitable for the confirmation and quantification of gossypol residue in edible vegetable oil.

Global m-Equivariant Solutions of Nematic Liquid Crystal Flows in Dimension Two

NASA Astrophysics Data System (ADS)

Chen, Yuan; Yu, Yong

2017-11-01

In this article we construct a global solution of the simplified Ericksen-Leslie system. We show that the velocity of the solution can be decomposed into the sum of three parts. The main flow is governed by the Oseen vortex with the same circulation Reynolds number as the initial fluid. The secondary flow has finite kinetic energy and decay in the speed (1 + t)-2 as t → ∞. The third part is a minor flow whose kinetic energy decays faster than the secondary flow. As for the orientation variable, our solution has a phase function which diverges logarithmically to ∞ as t → ∞. This indicates that the orientation variable will keep rotating around the z-axis while t → ∞. This phenomenon results from a non-trivial coupling between the orientation variable and a fluid with a non-zero circulation Reynolds number.

Computational Investigation of the NASA Cascade Cyclonic Separation Device

NASA Technical Reports Server (NTRS)

Hoyt, Nathaniel C.; Kamotani, Yasuhiro; Kadambi, Jaikrishnan; McQuillen, John B.; Sankovic, John M.

2008-01-01

Devices designed to replace the absent buoyancy separation mechanism within a microgravity environment are of considerable interest to NASA as the functionality of many spacecraft systems are dependent on the proper sequestration of interpenetrating gas and liquid phases. Inasmuch, a full multifluid Euler-Euler computational fluid dynamics investigation has been undertaken to evaluate the performance characteristics of one such device, the Cascade Cyclonic Separator, across a full range of inlet volumetric quality with combined volumetric injection rates varying from 1 L/min to 20 L/min. These simulations have delimited the general modes of operation of this class of devices and have proven able to describe the complicated vortex structure and induced pressure gradients that arise. The computational work has furthermore been utilized to analyze design modifications that enhance the overall performance of these devices. The promising results indicate that proper CFD modeling may be successfully used as a tool for microgravity separator design.

Connecting Dissipation and Phase Slips in a Josephson Junction between Fermionic Superfluids.

PubMed

Burchianti, A; Scazza, F; Amico, A; Valtolina, G; Seman, J A; Fort, C; Zaccanti, M; Inguscio, M; Roati, G

2018-01-12

We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.

Vortex spin-torque oscillator stabilized by phase locked loop using integrated circuits

NASA Astrophysics Data System (ADS)

Kreissig, Martin; Lebrun, R.; Protze, F.; Merazzo-Jaimes, K.; Hem, J.; Vila, L.; Ferreira, R.; Cyrille, M.-C.; Ellinger, F.; Cros, V.; Ebels, U.; Bortolotti, P.

2017-05-01

Spin-torque nano-oscillators (STO) are candidates for the next technological implementation of spintronic devices in commercial electronic systems. For use in microwave applications, improving the noise figures by efficient control of their phase dynamics is a mandatory requirement. In order to achieve this, we developed a compact phase locked loop (PLL) based on custom integrated circuits (ICs) and demonstrate that it represents an efficient way to reduce the phase noise level of a vortex based STO. The advantage of our approach to phase stabilize STOs is that our compact system is highly reconfigurable e.g. in terms of the frequency divider ratio N, RF gain and loop gain. This makes it robust against device to device variations and at the same time compatible with a large range of STOs. Moreover, by taking advantage of the natural highly non-isochronous nature of the STO, the STO frequency can be easily controlled by e.g. changing the divider ratio N.

Connecting Dissipation and Phase Slips in a Josephson Junction between Fermionic Superfluids

NASA Astrophysics Data System (ADS)

Burchianti, A.; Scazza, F.; Amico, A.; Valtolina, G.; Seman, J. A.; Fort, C.; Zaccanti, M.; Inguscio, M.; Roati, G.

2018-01-01

We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.

Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3

NASA Technical Reports Server (NTRS)

Santee, M. L.; Read, W. G.; Waters, J. W.; Froidevaux, L.; Manney, G. L.; Flower, D. A.; Jarnot, R. F.; Harwood, R. S.; Peckham, G. E.

1995-01-01

Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone 'hole' is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

Reactive nitrogen, ozone, and nitrate aerosols observed in the Arctic stratosphere in January 1990

NASA Technical Reports Server (NTRS)

Kondo, Y.; Aimedieu, P.; Koike, M.; Iwasaka, Y.; Newman, P. A.; Schmidt, U.; Matthews, W. A.; Hayashi, M.; Sheldon, W. R.

1992-01-01

Ozone mixing ratios in the vicinity of the 525-K potential temperature surface in January and early February of 1990 were observed to decrease sharply across the edge of the vortex boundary, where the vortex position was estimated from Ertel's potential vorticity. The changes in NO(y) mixing ratio with respect to altitude measured on January 18 and 31 were quite well correlated with those of ozone between 15 and 24 km, indicating that NO(y) also had a large gradient across the edge of the vortex. This is interpreted as being mainly due to the significant denitrification that occurred inside the vortex. The total amount of gas and particulate phase HNO3 was close to the NO(y) amount at the altitude of the 22- to 23-km region, suggesting that the conversion of non-HNO3 reactive nitrogen to HNO3 had occurred with a PSC.

Unsteady hydraulic simulation of the cavitating part load vortex rope in Francis turbines

NASA Astrophysics Data System (ADS)

Brammer, J.; Segoufin, C.; Duparchy, F.; Lowys, P. Y.; Favrel, A.; Avellan, F.

2017-04-01

For Francis turbines at part load operation a helical vortex rope is formed due to the swirling nature of the flow exiting the runner. This vortex creates pressure fluctuations which can lead to power swings, and the unsteady loading can lead to fatigue damage of the runner. In the case that the vortex rope cavitates there is the additional risk that hydro-acoustic resonance can occur. It is therefore important to be able to accurately simulate this phenomenon to address these issues. In this paper an unsteady, multi-phase CFD model was used to simulate two part-load operating points, for two different cavitation conditions. The simulation results were validated with test-rig data, and showed very good agreement. These results also served as an input for FEA calculations and fatigue analysis, which are presented in a separate study.

Generation of topologically diverse acoustic vortex beams using a compact metamaterial aperture

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

Naify, Christina J., E-mail: christina.naify@nrl.navy.mil; Rohde, Charles A.; Martin, Theodore P.

2016-05-30

Here, we present a class of metamaterial-based acoustic vortex generators which are both geometrically simple and broadly tunable. The aperture overcomes the significant limitations of both active phasing systems and existing passive coded apertures. The metamaterial approach generates topologically diverse acoustic vortex waves motivated by recent advances in leaky wave antennas by wrapping the antenna back upon itself to produce an acoustic vortex wave antenna. We demonstrate both experimentally and analytically that this single analog structure is capable of creating multiple orthogonal orbital angular momentum modes using only a single transducer. The metamaterial design makes the aperture compact, with amore » diameter nearly equal to the excitation wavelength and can thus be easily integrated into high-density systems. Applications range from acoustic communications for high bit-rate multiplexing to biomedical devices such as microfluidic mixers.« less

Vortex knots in tangled quantum eigenfunctions

PubMed Central

Taylor, Alexander J.; Dennis, Mark R.

2016-01-01

Tangles of string typically become knotted, from macroscopic twine down to long-chain macromolecules such as DNA. Here, we demonstrate that knotting also occurs in quantum wavefunctions, where the tangled filaments are vortices (nodal lines/phase singularities). The probability that a vortex loop is knotted is found to increase with its length, and a wide gamut of knots from standard tabulations occur. The results follow from computer simulations of random superpositions of degenerate eigenstates of three simple quantum systems: a cube with periodic boundaries, the isotropic three-dimensional harmonic oscillator and the 3-sphere. In the latter two cases, vortex knots occur frequently, even in random eigenfunctions at relatively low energy, and are constrained by the spatial symmetries of the modes. The results suggest that knotted vortex structures are generic in complex three-dimensional wave systems, establishing a topological commonality between wave chaos, polymers and turbulent Bose–Einstein condensates. PMID:27468801

Structuring Stokes correlation functions using vector-vortex beam

NASA Astrophysics Data System (ADS)

Kumar, Vijay; Anwar, Ali; Singh, R. P.

2018-01-01

Higher order statistical correlations of the optical vector speckle field, formed due to scattering of a vector-vortex beam, are explored. Here, we report on the experimental construction of the Stokes parameters covariance matrix, consisting of all possible spatial Stokes parameters correlation functions. We also propose and experimentally realize a new Stokes correlation functions called Stokes field auto correlation functions. It is observed that the Stokes correlation functions of the vector-vortex beam will be reflected in the respective Stokes correlation functions of the corresponding vector speckle field. The major advantage of proposing Stokes correlation functions is that the Stokes correlation function can be easily tuned by manipulating the polarization of vector-vortex beam used to generate vector speckle field and to get the phase information directly from the intensity measurements. Moreover, this approach leads to a complete experimental Stokes characterization of a broad range of random fields.

A Critical Review of the Transport and Decay of Wake Vortices in Ground Effect

NASA Technical Reports Server (NTRS)

Sarpkaya, T.

2004-01-01

This slide presentation reviews the transport and decay of wake vortices in ground effect and cites a need for a physics-based parametric model. The encounter of a vortex with a solid body is always a complex event involving turbulence enhancement, unsteadiness, and very large gradients of velocity and pressure. Wake counter in ground effect is the most dangerous of them all. The interaction of diverging, area-varying, and decaying aircraft wake vortices with the ground is very complex because both the vortices and the flow field generated by them are altered to accommodate the presence of the ground (where there is very little room to maneuver) and the background turbulent flow. Previous research regarding vortex models, wake vortex decay mechanisms, time evolution within in ground effect of a wake vortex pair, laminar flow in ground effect, and the interaction of the existing boundary layer with a convected vortex are reviewed. Additionally, numerical simulations, 3-dimensional large-eddy simulations, a probabilistic 2-phase wake vortex decay and transport model and a vortex element method are discussed. The devising of physics-based, parametric models for the prediction of (operational) real-time response, mindful of the highly three-dimensional and unsteady structure of vortices, boundary layers, atmospheric thermodynamics, and weather convective phenomena is required. In creating a model, LES and field data will be the most powerful tools.

Periodic vortex pinning by regular structures in Nb thin films: magnetic vs. structural effects

NASA Astrophysics Data System (ADS)

Montero, Maria Isabel; Jonsson-Akerman, B. Johan; Schuller, Ivan K.

2001-03-01

The defects present in a superconducting material can lead to a great variety of static and dynamic vortex phases. In particular, the interaction of the vortex lattice with regular arrays of pinning centers such as holes or magnetic dots gives rise to commensurability effects. These commensurability effects can be observed in the magnetoresistance and in the critical current dependence with the applied field. In recent years, experimental results have shown that there is a dependence of the periodic pinning effect on the properties of the vortex lattice (i.e. vortex-vortex interactions, elastic energy and vortex velocity) and also on the dots characteristics (i.e. dot size, distance between dots, magnetic character of the dot material, etc). However, there is not still a good understanding of the nature of the main pinning mechanisms by the magnetic dots. To clarify this important issue, we have studied and compared the periodic pinning effects in Nb films with rectangular arrays of Ni, Co and Fe dots, as well as the pinning effects in a Nb film deposited on a hole patterned substrate without any magnetic material. We will discuss the differences on pinning energies arising from magnetic effects as compared to structural effects of the superconducting film. This work was supported by NSF and DOE. M.I. Montero acknowledges postdoctoral fellowship by the Secretaria de Estado de Educacion y Universidades (Spain).

Graphene oxide/Fe3O4 as sorbent for magnetic solid-phase extraction coupled with liquid chromatography to determine 2,4,6-trinitrotoluene in water samples.

PubMed

Costa Dos Reis, Luciana; Vidal, Lorena; Canals, Antonio

2017-04-01

A fast, simple, economical, and environmentally friendly magnetic solid-phase extraction (MSPE) procedure has been developed to preconcentrate 2,4,6-trinitrotoluene (TNT) from water samples prior to determination by liquid chromatography-UV-Vis employing graphene oxide/Fe 3 O 4 nanocomposite as sorbent. The nanocomposite synthesis was investigated, and the MSPE was optimized by a multivariate approach. The optimum MSPE conditions were 40 mg of nanocomposite, 10 min of vortex extraction, 1 mL of acetonitrile as eluent, and 6 min of desorption in an ultrasonic bath. Under the optimized experimental conditions, the method was evaluated to obtain a preconcentration factor of 153. The linearity of the method was studied from 1 to 100 μg L -1 (N = 5), obtaining a correlation coefficient of 0.994. The relative standard deviation and limit of detection were found to be 12% (n = 6, 10 μg L -1 ) and 0.3 μg L -1 , respectively. The applicability of the method was investigated, analyzing three types of water samples (i.e., reservoir and drinking water and effluent wastewater) and recovery values ranged between 87 and 120% (50 μg L -1 spiking level), showing that the matrix had a negligible effect upon extraction. Finally, the semiquantitative Eco-Scale metrics confirmed the greenness of the developed method.

Pinning time statistics for vortex lines in disordered environments.

PubMed

Dobramysl, Ulrich; Pleimling, Michel; Täuber, Uwe C

2014-12-01

We study the pinning dynamics of magnetic flux (vortex) lines in a disordered type-II superconductor. Using numerical simulations of a directed elastic line model, we extract the pinning time distributions of vortex line segments. We compare different model implementations for the disorder in the surrounding medium: discrete, localized pinning potential wells that are either attractive and repulsive or purely attractive, and whose strengths are drawn from a Gaussian distribution; as well as continuous Gaussian random potential landscapes. We find that both schemes yield power-law distributions in the pinned phase as predicted by extreme-event statistics, yet they differ significantly in their effective scaling exponents and their short-time behavior.

Magnetotransport study of topological superconductor Cu0.10Bi2Se3 single crystal

NASA Astrophysics Data System (ADS)

Li, M. T.; Fang, Y. F.; Zhang, J. C.; Yi, H. M.; Zhou, X. J.; Lin, C. T.

2018-03-01

We report a magnetotransport study of vortex-pinning in Cu0.10Bi2Se3 single crystal. The sample is demonstrated to be in clean limit and absent of Pauli spin-limiting effect. Interestingly, the resistivity versus magnetic field shows an anomalously pronounced increase when approaching the superconducting-normal state boundary for both {{B}app}\\parallel ab and {{B}app}\\parallel c configurations. We have investigated the flux-flowing behavior under various magnetic fields and temperatures, enabling us to establish its anisotropic vortex phase diagram. Our results suggest the Cu0.10Bi2Se3 can be served as one unique material for exploring exotic surface vortex states in topological superconductors.

Critical current and electric transport properties of superconducting epitaxial Nb(Ti)N submicron structures

NASA Astrophysics Data System (ADS)

Klimov, A.; Słysz, W.; Guziewicz, M.; Kolkovsky, V.; Wegrzecki, M.; Bar, J.; Marchewka, M.; Seredyński, B.

2016-12-01

Critical current and current-voltage characteristics of epitaxial Nb(Ti)N submicron ultrathin structures were measured as function of temperature. For 700-nm-wide bridge we found current-driven vortex de-pinning at low temperatures and thermally activated flux flow closer to the transition temperature, as the limiting factors for the critical current density. For 100-nm-wide meander we observed combination of phase-slip activation and vortex-anti-vortex pair (VAP) thermal excitation. Our Nb(Ti)N meander structure demonstrates high de-pairing critical current densities 107 A/cm2 at low temperatures, but the critical currents are much smaller due to presence of the local constrictions.

Investigation of the Vortex States of Sr2RuO4-Ru Eutectic Microplates Using DC-SQUIDs

NASA Astrophysics Data System (ADS)

Sakuma, Daisuke; Nago, Yusuke; Ishiguro, Ryosuke; Kashiwaya, Satoshi; Nomura, Shintaro; Kono, Kimitoshi; Maeno, Yoshiteru; Takayanagi, Hideaki

2017-11-01

We investigated the magnetic properties of a Sr2RuO4-Ru eutectic microplate containing a single Ru-inclusion using micrometer-sized DC-SQUIDs (direct-current superconducting quantum interference devices). A phase frustration at the interface between chiral p-wave superconducting Sr2RuO4 and s-wave superconducting Ru is expected to cause novel magnetic vortex states such as the spontaneous Ru-center vortex under zero magnetic field [as reported by H. Kaneyasu and M. Sigrist, J. Phys. Soc. Jpn. 79, 053706 (2010)]. Our experimental results show no positive evidence for such a spontaneous vortex state. However, in an applied field, an abrupt change in the magnetic flux distribution was observed at a superconducting transition of Ru. The flux distribution is clarified by comparing our experimental results with electromagnetic field simulations in our sample geometry. We discuss the transition of the vortex states and the superconducting coupling at the Sr2RuO4/Ru interface.

Vectorial structures of linear-polarized Butterfly-Gauss vortex beams in the far zone

NASA Astrophysics Data System (ADS)

Cheng, Ke; Zhou, Yan; Lu, Gang; Yao, Na; Zhong, Xianqiong

2018-05-01

By introducing the Butterfly catastrophe to optics, the far-zone vectorial structures of Butterfly-Gauss beam with vortex and non-vortex are studied using the angular spectrum representation and stationary phase method. The influence of topological charge, linear-polarized angle, off-axis distance and scaling length on the far-zone vectorial structures, especially in the Poynting vector and angular momentum density of the corresponding beam is emphasized. The results show that the embedded optical vortex at source plane lead to special dark zones in the far zone, where the number of dark zone equals the absolute value of topological charge of optical vortex. Furthermore, the symmetry and direction of the special dark zones can be controlled by off-axis distance and scaling length, respectively. The linear-polarized angle adjusts only the Poynting vectors of TE and TM terms, but it does not affect those of whole beam. Finally, the vectorial expressions also indicate that the total angular momentum density is certainly zero owing to the far-zone stable structures rather than rotation behaviors.

High helicity vortex conversion in a rubidium vapor

NASA Astrophysics Data System (ADS)

Chopinaud, Aurélien; Jacquey, Marion; Viaris de Lesegno, Bruno; Pruvost, Laurence

2018-06-01

The orbital angular momentum (OAM) of light is a quantity explored for communication and quantum technology, its key strength being a wide set of values offering a large basis for quantum working. In this context we have studied the vortex conversion from a red optical vortex to a blue one, for OAMs ranging -30 to +30 . The conversion is realized in a rubidium vapor, via the 5 S1 /2-5 D5 /285Rb two-photon transition done with a Gaussian beam at 780 nm plus a Laguerre-Gaussian beam at 776 nm with the OAM ℓ , producing a radiation at 420 nm . With copropagating input beams, we demonstrate a conversion from red to blue for high-ℓ input vortices. We show that the output blue vortex respects the azimuthal phase matching, has a size determined by the product of the input beams, and a power decreasing with ℓ , in agreement with their overlap. Its propagation indicates that the generated blue wave is a nearly pure Laguerre-Gaussian mode. The vortex converter thus permits a correct OAM transmission.

Spatiotemporal characterization of ultrashort optical vortex pulses

NASA Astrophysics Data System (ADS)

Miranda, Miguel; Kotur, Marija; Rudawski, Piotr; Guo, Chen; Harth, Anne; L'Huillier, Anne; Arnold, Cord L.

2017-12-01

We use a spiral phase plate to generate few-cycle optical vortices from an ultrafast titanium:sapphire oscillator and characterize them in the spatiotemporal domain with a recently introduced technique based on spatially resolved Fourier transform spectrometry. The performance of this simple approach to the generation of optical vortices is analysed from a wavelength-dependent perspective as well as in the spatiotemporal domain, allowing us to characterize ultrashort vortex pulses in space, frequency and time.

White-light optical vortex coronagraph

NASA Astrophysics Data System (ADS)

Kanburapa, Prachyathit

An optical vortex is characterized by a dark core of destructive interference in a light beam. One of the methods commonly employed to create an optical vortex is by using a computer-generated hologram. A vortex hologram pattern is computed from the interference pattern between a reference plane wave and a vortex wave, resulting in a forked grating pattern. In astronomy, an optical vortex coronagraph is one of the most promising high contrast imaging techniques for the direct imaging of extra-solar planets. Direct imaging of extra-solar planets is a challenging task since the brightness of the parent star is extremely high compared to its orbiting planets. The on-axis light from the parent star gets diffracted in the coronagraph, forming a "ring of fire" pattern, whereas the slightly off-axis light from the planet remains intact. Lyot stop can then be used to block the ring of fire pattern, thus allowing only the planetary light to get through to the imaging camera. Contrast enhancements of 106 or more are possible, provided the vortex lens (spiral phase plate) has exceptional optical quality. By using a vortex hologram with a 4 microm pitch, and an f/300 focusing lens, we were able to demonstrate the creation of a "ring of fire" using a white light emitting diode as a source. A dispersion compensating linear diffraction grating of 4 microm pitch was used to bring the rings together to form a single white light ring of fire. To our knowledge, this is the first time a vortex hologram based OVC has been demonstrated, resulting in a well-formed white light ring of fire. Experimental results show measured power contrast of 1/515 when HeNe laser source was used as a light source and 1/77 when using a white light emitting diode.

Nonlinear Analysis of Two-phase Circumferential Motion in the Ablation Circumstance

NASA Astrophysics Data System (ADS)

Xiao-liang, Xu; Hai-ming, Huang; Zi-mao, Zhang

2010-05-01

In aerospace craft reentry and solid rocket propellant nozzle, thermal chemistry ablation is a complex process coupling with convection, heat transfer, mass transfer and chemical reaction. Based on discrete vortex method (DVM), thermal chemical ablation model and particle kinetic model, a computational module dealing with the two-phase circumferential motion in ablation circumstance is designed, the ablation velocity and circumferential field can be thus calculated. The calculated nonlinear time series are analyzed in chaotic identification method: relative chaotic characters such as correlation dimension and the maximum Lyapunov exponent are calculated, fractal dimension of vortex bulbs and particles distributions are also obtained, thus the nonlinear ablation process can be judged as a spatiotemporal chaotic process.

Quantum oscillations in a biaxial pair density wave state.

PubMed

Norman, M R; Davis, J C Séamus

2018-05-22

There has been growing speculation that a pair density wave state is a key component of the phenomenology of the pseudogap phase in the cuprates. Recently, direct evidence for such a state has emerged from an analysis of scanning tunneling microscopy data in halos around the vortex cores. By extrapolation, these vortex halos would then overlap at a magnetic-field scale where quantum oscillations have been observed. Here, we show that a biaxial pair density wave state gives a unique description of the quantum oscillation data, bolstering the case that the pseudogap phase in the cuprates may be a pair density wave state. Copyright © 2018 the Author(s). Published by PNAS.

Quantum turbulence in cold multicomponent matter

NASA Astrophysics Data System (ADS)

Pshenichnyuk, Ivan A.

2018-02-01

Quantum vortices are pivotal for understanding of phenomena in quantum hydrodynamics. Vortices were observed in different physical systems like trapped dilute Bose-Einstein condensates, liquid helium, exciton-polariton condensates and other types of systems. Foreign particles attached to the vortices often serve for a visualization of the vortex shape and kinematics in superfluid experiments. Fascinating discoveries were made in the field of cold quantum mixtures, where vortices created in one component may interact with the other component. This works raise the fundamental question of the interaction between quantum vortices and matter. The generalized nonlinear Schrodinger equation based formalism is applied here to model three different processes involving the interaction of quantum vortices with foreign particles: propagation of a fast classical particle in a superfluid under the influence of sound waves, scattering of a single fermion by a quantized vortex line and dynamics of vortex pairs doped with heavy bosonic matter. The obtained results allow to to clarify the details of recent experiments and acquire a better understanding of the multicomponent quantum turbulence.

Analysis of nulling phase functions suitable to image plane coronagraphy

NASA Astrophysics Data System (ADS)

Hénault, François; Carlotti, Alexis; Vérinaud, Christophe

2016-07-01

Coronagraphy is a very efficient technique for identifying and characterizing extra-solar planets orbiting in the habitable zone of their parent star, especially in a space environment. An important family of coronagraphs is actually based on phase plates located at an intermediate image plane of the optical system, and spreading the starlight outside the "Lyot" exit pupil plane of the instrument. In this commutation we present a set of candidate phase functions generating a central null at the Lyot plane, and study how it propagates to the image plane of the coronagraph. These functions include linear azimuthal phase ramps (the well-known optical vortex), azimuthally cosine-modulated phase profiles, and circular phase gratings. Nnumerical simulations of the expected null depth, inner working angle, sensitivity to pointing errors, effect of central obscuration located at the pupil or image planes, and effective throughput including image mask and Lyot stop transmissions are presented and discussed. The preliminary conclusion is that azimuthal cosine functions appear as an interesting alternative to the classical optical vortex of integer topological charge.

Investigation of Thermocapillary Convection of High Prandtl Number Fluid Under Microgravity

NASA Technical Reports Server (NTRS)

Liang, Ruquan; Duan, Guangdong

2012-01-01

Thermocapillary convection in a liquid bridge, which is suspended between two coaxial disks under zero gravity, has been investigated numerically. The Navier-Stokes equations coupled with the energy conservation equation are solved on a staggered grid, and the level set approach is used to capture the free surface deformation of the liquid bridge. The velocity and temperature distributions inside the liquid bridge are analyzed. It is shown from this work that as the development of the thermocapillary convection, the center of the vortex inside the liquid bridge moves down and reaches an equilibrium position gradually. The temperature gradients in the regions near the upper center axis and the bottom cold corner are higher than those in the other regions.

Magnetic field controlled floating-zone single crystal growth of intermetallic compounds

NASA Astrophysics Data System (ADS)

Hermann, R.; Gerbeth, G.; Priede, J.

2013-03-01

Radio-frequency (RF) floating zone single crystal growth is an important technique for the preparation of single bulk crystals. The advantage of the floating-zone method is the crucible-free growth of single crystals of reactive materials with high melting points. The strong heat diffusion on the surface, as well as the melt convection in the molten zone due to induction heating, often leads to an undesired solid-liquid interface geometry with a concave (towards the solid phase) outer rim. These concave parts aggravate the single crystal growth over the full cross-section. A two-phase stirrer was developed at IFW Dresden in order to avoid the problems connected with these concave parts. It acts as a magnetic field pump and changes the typical double vortex structure to a single roll structure, thus pushing hot melt into the regions where the concave parts may arise. The current in the secondary coil is induced by the primary coil, and the capacitor and the resistance of the secondary circuit are adjusted to get a stable 90 degree phase-shift between the coil currents. Single crystal growth of industrial relevant RuAl and TiAl intermetallic compounds was performed based on the material parameters and using the adjusted two-phase stirrer. Very recently, the magnetic system was applied to the crystal growth of biocompatible TiNb alloys and antiferromagnetic Heusler MnSi compounds.

The metal-organic framework HKUST-1 as efficient sorbent in a vortex-assisted dispersive micro solid-phase extraction of parabens from environmental waters, cosmetic creams, and human urine.

PubMed

Rocío-Bautista, Priscilla; Martínez-Benito, Carla; Pino, Verónica; Pasán, Jorge; Ayala, Juan H; Ruiz-Pérez, Catalina; Afonso, Ana M

2015-07-01

Three metal-organic frameworks (MOFs), specifically HKUST-1, MOF-5, and MIL-53(Al), have been synthetized, characterized, studied and compared in a vortex-assisted dispersive micro-solid-phase extraction (VA-D-µ-SPE) procedure in combination with high-performance liquid chromatography (HPLC) with diode-array detection (DAD) for determining seven parabens in environmental waters (tap water, swimming pool water, and water coming from a spa pool), human urine (from two volunteers), and cosmetic creams (two commercial brands). Experimental parameters, such as nature and amount of MOF, sample volume, nature of elution solvent and its amount, vortex and centrifugation time, among others, were properly optimized. HKUST-1 was the most adequate MOF to work with. Detection limits for the overall method down to 0.1 μgL(-1) for butylparaben (BPB) and benzylparaben (BzPB) were obtained, with determination coefficients (R(2)) higher than 0.9966 for a range of 0.5-147 μgL(-1) (depending on the paraben), average relative recoveries (RR, in %) of 80.3% at the low spiked level (7 μgL(-1)), and relative standard deviation (RSD) values below 10% also at the low spiked level. The strength of the affinity between HKUST-1 and parabens was evaluated, and it ranged from 33.5% for isopropylparaben (iPPB) to 77.0% for isobutylparaben (iBPB). When analyzing complex environmental waters, RR values of 78%, inter-day precision values (as RSD) lower than 15%, and intra-day precision values lower than 7.8% were obtained, despite the observed matrix effect. When analyzing cosmetic creams, parabens were detected, with contents ranging from 0.14 ± 0.01 μgg(-1) for EPB in the healing cream analyzed to 1.12 ± 0.07 mgg(-1) for MPB in the mask cream analyzed, with precision values (RSD) lower than 12% and RR values from 63.7% for propylparaben (PPB) to 121% for iPPB. When analyzing human urine, no parabens were detected but the method could be performed with RSD values lower than 19%. These results show the adequateness of MOFs as sorbents in VA-D-µ-SPE procedures despite sample complexity. Copyright © 2015 Elsevier B.V. All rights reserved.

Electronic properties of high-temperature superconductors and novel carbon-based conductors and superconductors

NASA Astrophysics Data System (ADS)

Fuhrer, Michael Sears

This thesis is divided into three sections. The first section discusses the electrical transport properties of a highly anisotropic high temperature superconductor, Bi2Sr2CaCu2O8, in magnetic fields. High temperature superconductivity has greatly expanded the study of vortex matter: the state of the quantized magnetic field excitations, or vortices, in a superconductor. The effects of tilted fields and fields parallel to the planes are studied: striking deviations from the expectations of a simple anisotropic superconductivity model are found, indicating that the layered structure of high temperature superconductors plays a significant role in determining the dynamics and phases of vortex matter. For the case of parallel magnetic fields, the Josephson vortex state, a new phase transition is identified, the melting of the Josephson vortex lattice. A mechanism for Josephson vortex lattice melting is proposed to explain the differences in the phase diagrams from the usual case of Abrikosov vortex lattice melting. The second section discusses experiments on C60-containing solids. A method for growing high quality single crystals of C60 is described. Isotopically pure single crystal samples of the fulleride superconductor Rb3C60 were synthesized in order to measure the carbon isotope effect on superconductivity. By measuring the superconducting transitions in the resistance of single crystals of Rb3C60, the carbon isotope effect was determined with unprecedented accuracy. Measurement of the isotope effect gives essential information for determination of the superconducting parameters, necessary for a complete theoretical picture of superconductivity in this material. New intercalated graphite compounds containing C60, and their electronic properties, are also discussed. The third section discusses the electrical transport and magnetotransport properties of mats of single-walled carbon nanotubes. Single-walled nanotubes are an intriguing new physical system: nanowires of pure carbon with nanometerscale diameters and lengths of microns. The previously unexplained low-temperature properties are shown to be due to localization. The radius of the localized states is determined, and the hopping conduction is found to be three-dimensional in nature. The magnetotransport also agrees with models of variable range hopping in two or greater dimensions, indicating that mats of single-walled nanotubes are well-connected metallic networks.

Vorticity dynamics in an intracranial aneurysm

NASA Astrophysics Data System (ADS)

Le, Trung; Borazjani, Iman; Sotiropoulos, Fotis

2008-11-01

Direct Numerical Simulation is carried out to investigate the vortex dynamics of physiologic pulsatile flow in an intracranial aneurysm. The numerical solver is based on the CURVIB (curvilinear grid/immersed boundary method) approach developed by Ge and Sotiropoulos, J. Comp. Physics, 225 (2007) and is applied to simulate the blood flow in a grid with 8 million grid nodes. The aneurysm geometry is extracted from MRI images from common carotid artery (CCA) of a rabbit (courtesy Dr.Kallmes, Mayo Clinic). The simulation reveals the formation of a strong vortex ring at the proximal end during accelerated flow phase. The vortical structure advances toward the aneurysm dome forming a distinct inclined circular ring that connects with the proximal wall via two long streamwise vortical structures. During the reverse flow phase, the back flow results to the formation of another ring at the distal end that advances in the opposite direction toward the proximal end and interacts with the vortical structures that were created during the accelerated phase. The basic vortex formation mechanism is similar to that observed by Webster and Longmire (1998) for pulsed flow through inclined nozzles. The similarities between the two flows will be discussed and the vorticity dynamics of an aneurysm and inclined nozzle flows will be analyzed.This work was supported in part by the University of Minnesota Supercomputing Institute.

Vortex assisted solid-phase extraction of lead(II) using orthorhombic nanosized Bi2WO6 as a sorbent.

PubMed

Baghban, Neda; Yilmaz, Erkan; Soylak, Mustafa

2017-12-07

Nanosized single crystal orthorhombic Bi 2 WO 6 was synthesized by a hydrothermal method and used as a sorbent for vortex assisted solid phase extraction of lead(II). The crystal and molecular structure of the sorbent was examined using XRD, Raman, SEM and SEM-EDX analysis. Various parameters affecting extraction efficiency were optimized by using multivariate design. The effect of diverse ions on the extraction also was studied. Lead was quantified by flame atomic absorption spectrometry (FAAS). The recoveries of lead(II) from spiked samples (at a typical spiking level of 200-400 ng·mL -1 ) are >95%. Other figures of merit includes (a) a detection limit of 6 ng·mL -1 , (b) a preconcentration factor of 50, (c) a relative standard deviation of 1.6%, and (d) and adsorption capacity of 6.6 mg·g -1 . The procedure was successfully applied to accurate determination of lead in (spiked) pomegranate and water samples. Graphical abstract Nanosized single crystal orthorhombic Bi 2 WO 6 was synthesized and characterized by a hydrothermal method and used as a sorbent for vortex assisted solid phase extraction of lead(II). The procedure was successfully applied to accurate determination of lead in (spiked) pomegranate and water samples.

Vortex Matter in Highly Strained Nb_{75}Zr_{25}: Analogy with Viscous Flow of Disordered Solids

NASA Astrophysics Data System (ADS)

Chandra, Jagdish; Manekar, Meghmalhar; Sharma, V. K.; Mondal, Puspen; Tiwari, Pragya; Roy, S. B.

2017-01-01

We present the results of magnetization and magneto-transport measurements in the superconducting state of an as-cast Nb_{75}Zr_{25} alloy. We also report the microstructure of our sample at various length scales by using optical, scanning electron and transmission electron microscopies. The information of microstructure is used to understand the flux pinning properties in the superconducting state within the framework of collective pinning. The magneto-transport measurements show a non-Arrhenius behaviour of the temperature- and field-dependent resistivity across the resistive transition and is understood in terms of a model for viscous flow of disordered solids which is popularly known as the `shoving model'. The activation energy for flux flow is assumed to be mainly the elastic energy stored in the flux-line lattice. The scaling of pinning force density indicates the presence of two pinning mechanisms of different origins. The elastic constants of the flux-line lattice are used to estimate the length scale of vortex lattice movement, or the volume displaced by the flux-line lattice. It appears that the vortex lattice displacement estimated from elastic energy considerations is of the same order of magnitude as that of the flux bundle hopping length during flux flow. Our results could provide possible directions for establishing a framework where vortex matter and glass-forming liquids or amorphous solids can be treated in a similar manner for understanding the phenomenon of viscous flow in disordered solids or more generally the pinning and depinning properties of elastic manifolds in random media. It is likely that the vortex molasses scenario is more suited to explain the vortex dynamics in conventional low-T_C superconductors.

Spin Superfluidity and Magnone BEC in He-3

NASA Astrophysics Data System (ADS)

Bunkov, Yury

2011-03-01

The spin superfluidity -- superfluidity in the magnetic subsystem of a condensed matter -- is manifested as the spontaneous phase-coherent precession of spins first discovered in 1984 in 3 He-B. This superfluid current of spins -- spin supercurrent -- is one more representative of superfluid currents known or discussed in other systems, such as the superfluid current of mass and atoms in superfluid 4 He; superfluid current of electric charge in superconductors; superfluid current of hypercharge in Standard Model of particle physics; superfluid baryonic current and current of chiral charge in quark matter; etc. Spin superfluidity can be described in terms of the Bose condensation of spin waves -- magnons. We discuss different states of magnon superfluidity with different types of spin-orbit coupling: in bulk 3 He-B; magnetically traped `` Q -balls'' at very low temperatures; in 3 He-A and 3 He-B immerged in deformed aerogel; etc. Some effects in normal 3 He can also be treated as a magnetic BEC of fermi liquid. A very similar phenomena can be observed also in a magnetic systems with dinamical frequensy shift, like MnC03 . We will discuss the main experimental signatures of magnons superfluidity: (i) spin supercurrent, which transports the magnetization on a macroscopic distance more than 1 cm long; (ii) spin current Josephson effect which shows interference between two condensates; (iii) spin current vortex -- a topological defect which is an analog of a quantized vortex in superfluids, of an Abrikosov vortex in superconductors, and cosmic strings in relativistic theories; (iv) Goldstone modes related to the broken U (1) symmetry -- phonons in the spin-superfluid magnon gas; etc. For recent review see Yu. M. Bunkov and G. E. Volovik J. Phys. Cond. Matter. 22, 164210 (2010) This work is partly supported by the Ministry of Education and Science of the Russian Federation (contract N 02.740.11.5217).

Overcoming the challenges of conventional dispersive liquid-liquid microextraction: analysis of THMs in chlorinated swimming pools.

PubMed

Faraji, Hakim; Helalizadeh, Masoumeh; Kordi, Mohammad Reza

2018-01-01

A rapid, simple, and sensitive approach to the analysis of trihalomethanes (THMs) in swimming pool water samples has been developed. The main goal of this study was to overcome or to improve the shortcomings of conventional dispersive liquid-liquid microextraction (DLLME) and to maximize the realization of green analytical chemistry principles. The method involves a simple vortex-assisted microextraction step, in the absence of the dispersive solvent, followed by salting-out effect for the elimination of the centrifugation step. A bell-shaped device and a solidifiable solvent were used to simplify the extraction solvent collection after phase separation. Optimization of the independent variables was performed by using chemometric methods in three steps. The method was statistically validated based on authentic guidance documents. The completion time for extraction was less than 8 min, and the limits of detection were in the range between 4 and 72 ng L -1 . Using this method, good linearity and precision were achieved. The results of THMs determination in different real samples showed that in some cases the concentration of total THMs was more than threshold values of THMs determined by accredited healthcare organizations. This method indicated satisfactory analytical figures of merit. Graphical Abstract A novel green microextraction technique for overcoming the challenges of conventional DLLME. The proposed procedure complies with the principles of green/sustainable analytical chemistry, comprising decreasing the sample size, making easy automation of the process, reducing organic waste, diminishing energy consumption, replacing toxic reagents with safer reagents, and enhancing operator safety.

Theory of the vortex-clustering transition in a confined two-dimensional quantum fluid

NASA Astrophysics Data System (ADS)

Yu, Xiaoquan; Billam, Thomas P.; Nian, Jun; Reeves, Matthew T.; Bradley, Ashton S.

2016-08-01

Clustering of like-sign vortices in a planar bounded domain is known to occur at negative temperature, a phenomenon that Onsager demonstrated to be a consequence of bounded phase space. In a confined superfluid, quantized vortices can support such an ordered phase, provided they evolve as an almost isolated subsystem containing sufficient energy. A detailed theoretical understanding of the statistical mechanics of such states thus requires a microcanonical approach. Here we develop an analytical theory of the vortex clustering transition in a neutral system of quantum vortices confined to a two-dimensional disk geometry, within the microcanonical ensemble. The choice of ensemble is essential for identifying the correct thermodynamic limit of the system, enabling a rigorous description of clustering in the language of critical phenomena. As the system energy increases above a critical value, the system develops global order via the emergence of a macroscopic dipole structure from the homogeneous phase of vortices, spontaneously breaking the Z2 symmetry associated with invariance under vortex circulation exchange, and the rotational SO (2 ) symmetry due to the disk geometry. The dipole structure emerges characterized by the continuous growth of the macroscopic dipole moment which serves as a global order parameter, resembling a continuous phase transition. The critical temperature of the transition, and the critical exponent associated with the dipole moment, are obtained exactly within mean-field theory. The clustering transition is shown to be distinct from the final state reached at high energy, known as supercondensation. The dipole moment develops via two macroscopic vortex clusters and the cluster locations are found analytically, both near the clustering transition and in the supercondensation limit. The microcanonical theory shows excellent agreement with Monte Carlo simulations, and signatures of the transition are apparent even for a modest system of 100 vortices, accessible in current Bose-Einstein condensate experiments.

3D laser printing by ultra-short laser pulses for micro-optical applications: towards telecom wavelengths

NASA Astrophysics Data System (ADS)

Ryu, Meguya; Mizeikis, Vygantas; Morikawa, Junko; Magallanes, Hernando; Brasselet, Etienne; Varapnickas, Simonas; Malinauskas, Mangirdas; Juodkazis, Saulius

2017-08-01

Three dimensional (3D) fast (< 0.5 hour) printing of micro-optical elements down to sub-wavelength resolution over 100 μm footprint areas using femtosecond (fs-)laser oscillator is presented. Using sub-1 nJ pulse energies, optical vortex generators made of polymerised grating segments with an azimuthally changing orientation have been fabricated in SZ2080 resist; width of polymerised rods was 150 nm and period 0.6-1 μm. Detailed phase retardance analysis was carried out manually with Berek compensator (under a white light illumination) and using an equivalent principle by an automated Abrio implementation at 546 nm. Direct experimental measurements of retardance was required since the period of the grating was comparable (or larger) than the wavelength of visible light. By gold sputtering, transmissive optical vortex generators were turned into reflective ones with augmented retardance, Δn × h defined by the form birefringence, Δn, and the height h = 2d where d is the thickness of the polymerised structure. Retardance reached 315 nm as measured with Berek compensator at visible wavelengths. Birefringent phase delays of π (or λ/2 in wavelength) required for high purity vortex generators can be made based on the proposed approach. Optical vortex generators for telecom wavelengths with sub-wavelength patterns of azimuthally oriented gratings are amenable by direct laser polymerisation.

Analysis of Poiseuille Flow Property in Two-Dimensional Mi-cro Channels of Microfluidic Pneumatic Micro-Valve

NASA Astrophysics Data System (ADS)

Yang, Shaohua; Long, Wei; Chen, Yajun

2018-03-01

In this paper, the control mechanism and mathematical description of the microfluidic flow in the microfluidic process of the PDMS membrane type pneumatic micro-valve were studied. The velocity and pressure variation law of the velocity field inside micro valve was analyzed by numerical simulation method. The influence of the two kinds of inlet drive modes on the working effect and the pressure flow characteristics of the pneumatic micro-valve was studied. The structure of the elastic solid valve diaphragm under the dual action of the airway and the liquid channel was analyzed. Deformation and stress distribution. The results show that the gas flow in the gas flow channel under the diaphragm by the vacuum part of the role of the formation of a suction gas vortex, pressure-driven mode was easier under the diaphragm to produce a strong gas vortex, resulting in internal and external pressure to promote diaphragm cut-off liquid channel; In the pressure pneumatic mode, the stress at both ends of the diaphragm was smaller, the membrane was not easy to tear failure.