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Sample records for vortex transformation performed

  1. Discrimination of orbital angular momentum modes of the terahertz vortex beam using a diffractive mode transformer.

    Science.gov (United States)

    Liu, Changming; Wei, Xuli; Niu, Liting; Wang, Kejia; Yang, Zhengang; Liu, Jinsong

    2016-06-13

    We present an efficient method to discriminate orbital angular momentum (OAM) of the terahertz (THz) vortex beam using a diffractive mode transformer. The mode transformer performs a log-polar coordinate transformation of the input THz vortex beam, which consists of two 3D-printed diffractive elements. A following lens separates each transformed OAM mode to a different lateral position in its focal plane. This method enables a simultaneous measurement over multiple OAM modes of the THz vortex beam. We experimentally demonstrate the measurement of seven individual OAM modes and two multiplexed OAM modes, which is in good agreement with simulations.

  2. Normal modes and mode transformation of pure electron vortex beams.

    Science.gov (United States)

    Thirunavukkarasu, G; Mousley, M; Babiker, M; Yuan, J

    2017-02-28

    Electron vortex beams constitute the first class of matter vortex beams which are currently routinely produced in the laboratory. Here, we briefly review the progress of this nascent field and put forward a natural quantum basis set which we show is suitable for the description of electron vortex beams. The normal modes are truncated Bessel beams (TBBs) defined in the aperture plane or the Fourier transform of the transverse structure of the TBBs (FT-TBBs) in the focal plane of a lens with the said aperture. As these modes are eigenfunctions of the axial orbital angular momentum operator, they can provide a complete description of the two-dimensional transverse distribution of the wave function of any electron vortex beam in such a system, in analogy with the prominent role Laguerre-Gaussian (LG) beams played in the description of optical vortex beams. The characteristics of the normal modes of TBBs and FT-TBBs are described, including the quantized orbital angular momentum (in terms of the winding number l) and the radial index p>0. We present the experimental realization of such beams using computer-generated holograms. The mode analysis can be carried out using astigmatic transformation optics, demonstrating close analogy with the astigmatic mode transformation between LG and Hermite-Gaussian beams.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Author(s).

  3. Optimizing the performance of a data vortex interconnection network

    Science.gov (United States)

    Shacham, Assaf; Bergman, Keren

    2007-04-01

    The definition of the data vortex architecture leaves broad room for decisions regarding the exact design point required for achieving a desired performance level. A detailed simulation-based study of various parameters that affect a data vortex interconnection network's performance is reported. Three implementations are compared by acceptance rate, latency, and cost.

  4. COMPARATIVE ANALYSIS OF PERFORMANCE CHARACTERISTICS OF JET VORTEX TYPE SUPERCHAGES

    Directory of Open Access Journals (Sweden)

    A. Rogovyi

    2016-06-01

    Full Text Available On the basis of mathematical modeling there was carried out a comparative analysis of characteristics of jet vortex type superchargers. Dependences of the energy performance of vortex ejector on the geometry parameters and the largest values in terms of efficiency as well as the coefficient of ejection are analyzed. There were built combined characteristics of vortex chamber pumps and vortex ejectors. Vortex chamber pump has advantage pressure in an exit channel over the vortex ejector, consequently there is a more effective power transmission from a working medium, besides the withdrawal of pumping medium in a tangential channel allows to avoid energy losses owing to rotation of a stream in an exit channel.

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

    Science.gov (United States)

    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

  6. Influence of Structural Parameters on the Performance of Vortex Valve Variable-Thrust Solid Rocket Motor

    Science.gov (United States)

    Wei, Xianggeng; Li, Jiang; He, Guoqiang

    2017-04-01

    The vortex valve solid variable thrust motor is a new solid motor which can achieve Vehicle system trajectory optimization and motor energy management. Numerical calculation was performed to investigate the influence of vortex chamber diameter, vortex chamber shape, and vortex chamber height of the vortex valve solid variable thrust motor on modulation performance. The test results verified that the calculation results are consistent with laboratory results with a maximum error of 9.5%. The research drew the following major conclusions: the optimal modulation performance was achieved in a cylindrical vortex chamber, increasing the vortex chamber diameter improved the modulation performance of the vortex valve solid variable thrust motor, optimal modulation performance could be achieved when the height of the vortex chamber is half of the vortex chamber outlet diameter, and the hot gas control flow could result in an enhancement of modulation performance. The results can provide the basis for establishing the design method of the vortex valve solid variable thrust motor.

  7. The Vortex and the Line: Performative Gestures in Allen Ginsberg's ‘Wichita Vortex Sutra’

    DEFF Research Database (Denmark)

    Sørensen, Bent

    and their identity politics… Queering the straight lines of Modernism, Allen Ginsberg suggests in his long poem about America and the Vietnam War, ‘Wichita Vortex Sutra’, that lying media discourses and corrupt political and military statements about the necessity of participation in the war may be cancelled out...... by a poet performing the simple, yet impossible speech act of declaring the end of the war, and in doing so queering the original declaratory speech act of the executive power. The poet must enter intrepidly the vortex of lies told by the voices disseminated by the media on behalf of politicians, authority...... figures and benighted members of the general public, utter a few lines of magic spells, and after this performative gesture the war will end of its own accord. The vehicle of this speech act is proposed to be the Sutra, a scripture consisting of a ‘string’ or ‘thread’ of aphoristic statements designed...

  8. Analytical and numerical performance models of a Heisenberg Vortex Tube

    Science.gov (United States)

    Bunge, C. D.; Cavender, K. A.; Matveev, K. I.; Leachman, J. W.

    2017-12-01

    Analytical and numerical investigations of a Heisenberg Vortex Tube (HVT) are performed to estimate the cooling potential with cryogenic hydrogen. The Ranque-Hilsch Vortex Tube (RHVT) is a device that tangentially injects a compressed fluid stream into a cylindrical geometry to promote enthalpy streaming and temperature separation between inner and outer flows. The HVT is the result of lining the inside of a RHVT with a hydrogen catalyst. This is the first concept to utilize the endothermic heat of para-orthohydrogen conversion to aid primary cooling. A review of 1st order vortex tube models available in the literature is presented and adapted to accommodate cryogenic hydrogen properties. These first order model predictions are compared with 2-D axisymmetric Computational Fluid Dynamics (CFD) simulations.

  9. Starting Vortex Identified as Key to Unsteady Ejector Performance

    Science.gov (United States)

    Paxson, Daniel E.

    2004-01-01

    Unsteady ejectors are currently under investigation for use in some pulse-detonation-engine-based propulsion systems. Experimental measurements made in the past, and recently at the NASA Glenn Research Center, have demonstrated that thrust augmentation can be enhanced considerably when the driver is unsteady. In ejector systems, thrust augmentation is defined as = T(sup Total)/T(sup j), where T(sup Total) is the total thrust of the combined ejector and driving jet and T(sup j) is the thrust due to the driving jet alone. There are three images in this figure, one for each of the named thrust sources. The images are color contours of measured instantaneous vorticity. Each image is an ensemble average of at least 150 phase-locked measurements. The flow is from right to left, and the shape and location of each driver is shown on the far right of each image. The emitted vortex is a clearly defined "doughnut" of highly vortical (spinning) flow. In these planar images, the vortex appears as two distorted circles, one above, and one below the axis of symmetry. Because they are spinning in the opposite direction, the two circles have vorticity of opposite sign and thus are different colors. There is also a rectangle shown in each image. Its width represents the ejector diameter that was found experimentally to yield the highest thrust augmentation. It is apparent that the optimal ejector diameter is that which just "captures" the vortex: that is, the diameter bounding the outermost edge of the vortex structure. The exact mechanism behind the enhanced performance is unclear; however, it is believed to be related to the powerful vortex emitted with each pulse of the unsteady driver. As such, particle imaging velocimetry (PIV) measurements were obtained for three unsteady drivers: a pulsejet, a resonance tube, and a speaker-driven jet. All the drivers were tested with ejectors, and all exhibited performance enhancement over similarly sized steady drivers. The characteristic

  10. Propeller and inflow vortex interaction : vortex response and impact on the propeller performance

    NARCIS (Netherlands)

    Yang, Y.; Zhou, T; Sciacchitano, A.; Veldhuis, L.L.M.; Eitelberg, G.

    2016-01-01

    The aerodynamic operating conditions of a propeller can include complex situations where vorticity from sources upstream can enter the propeller plane. In general, when the vorticity enters in a concentrated form of a vortex, the interaction between the vortex and blade is referred to as

  11. Optical Image Encryption Using Devil’s Vortex Toroidal Lens in the Fresnel Transform Domain

    Directory of Open Access Journals (Sweden)

    Hukum Singh

    2015-01-01

    Full Text Available We have carried out a study of optical image encryption in the Fresnel transform (FrT domain, using a random phase mask (RPM in the input plane and a phase mask based on devil’s vortex toroidal lens (DVTL in the frequency plane. The original images are recovered from their corresponding encrypted images by using the correct parameters of the FrT and the parameters of DVTL. The use of a DVTL-based structured mask enhances security by increasing the key space for encryption and also aids in overcoming the problem of axis alignment associated with an optical setup. The proposed encryption scheme is a lensless optical system and its digital implementation has been performed using MATLAB 7.6.0 (R2008a. The scheme has been validated for a grayscale and a binary image. The efficacy of the proposed scheme is verified by computing mean-squared-error (MSE between the recovered and the original images. We have also investigated the scheme’s sensitivity to the encryption parameters and examined its robustness against occlusion and noise attacks.

  12. Characterization method of unusual second-order-harmonic generation based on vortex transformation

    Science.gov (United States)

    Zhang, Chaojin; Wu, Erheng; Gu, Mingliang; Hu, Zhengfeng; Liu, Chengpu

    2017-09-01

    When a few-cycle laser beam nonresonantly propagates through an inversion-symmetric medium, beyond the usual odd-order harmonics in the transmission spectra, a well-defined spectral peak at twice the incident laser central frequency is disclosed [T. Tritschler et al., Phys. Rev. Lett. 90, 217404 (2003), 10.1103/PhysRevLett.90.217404]. Beyond the characterization method via the rf measurement of its carrier-envelope phase dependence, here a more direct mode of characterization is proposed by means of vortex transformation where a few-cycle vortex laser is adopted instead: One can easily clarify its origin as an usual third-order harmonic that appears to be a second-order harmonic, based on the criteria that the topological charge number of harmonics is directly proportional to its harmonic order.

  13. Analysis of the Aerodynamic Performance of Counter-Rotating Propeller by Means of Vortex Lattice Method

    OpenAIRE

    Saito, Shigeru; Mizobuchi, Yasuhiro; 齊藤 茂; 溝渕, 泰寛

    1990-01-01

    Aerodynamic performance of a counter-rotating propeller has been calculated by means of Vortex Lattice Method. The new wake system of the each rotor was constructed using a prescribed wake model by Kocurek-Berkowitz-Harris, which is well known as an empirical wake system of helicopter rotor with low aspect ratio blade. The votex filaments including a blade tip vortex were treated as vortex tube with the finite vortex core in order to avoid the numerical divergence in the calculation. The calc...

  14. On Bäcklund transformation and vortex filament equation for null Cartan curve in Minkowski 3-space

    Energy Technology Data Exchange (ETDEWEB)

    Grbović, Milica, E-mail: milica.grbovic@kg.ac.rs; Nešović, Emilija, E-mail: nesovickg@sbb.rs [University of Kragujevac, Faculty of Science, Department of Mathematics and Informatics (Serbia)

    2016-12-15

    In this paper we introduce Bäcklund transformation of a null Cartan curve in Minkowski 3-space as a transformation which maps a null Cartan helix to another null Cartan helix, congruent to the given one. We also give the sufficient conditions for a transformation between two null Cartan curves in the Minkowski 3-space such that these curves have equal constant torsions. By using the Da Rios vortex filament equation, based on localized induction approximation, we derive the vortex filament equation for a null Cartan curve and obtain evolution equation for it’s torsion. As an application, we show that Cartan’s frame vectors generate new solutions of the Da Rios vortex filament equation.

  15. Predicting optimum vortex tube performance using a simplified CFD model

    Energy Technology Data Exchange (ETDEWEB)

    Karimi-Esfahani, M; Fartaj, A.; Rankin, G.W. [Univ. of Windsor, Dept. of Mechanical, Automotive and Materials Engineering, Windsor, Ontario (Canada)]. E-mail: mki_60@hotmail.com

    2004-07-01

    The Ranque-Hilsch tube is a particular type of vortex tube device. The flow enters the device tangentially near one end and exits from the open ends of the tube. The inlet air is of a uniform temperature throughout while the outputs are of different temperatures. One outlet is hotter and the other is colder than the inlet air. This device has no moving parts and does not require any additional power for its operation other than that supplied to the device to compress the inlet air. It has, however, not been widely used, mainly because of its low efficiency. In this paper, a simplified 2-dimensional computational fluid dynamics model for the flow in the vortex tube is developed using FLUENT. This model makes use of the assumption of axial symmetry throughout the entire flow domain. Compared to a three-dimensional computational solution, the simplified model requires significantly less computational time. This is important because the model is to be used for an optimization study. A user-defined function is generated to implement a modified version of the k-epsilon model to account for turbulence. This model is validated by comparing a particular solution with available experimental data. The variation of cold temperature drop and efficiency of the device with orifice diameter, inlet pressure and cold mass flow ratio qualitatively agree with experimental results. Variation of these performance indices with tube length did not agree with the experiments for small values of tube length. However, it did agree qualitatively for large values. (author)

  16. Performance analysis of vortex based mixers for confined flows

    Science.gov (United States)

    Buschhagen, Timo

    The hybrid rocket is still sparsely employed within major space or defense projects due to their relatively poor combustion efficiency and low fuel grain regression rate. Although hybrid rockets can claim advantages in safety, environmental and performance aspects against established solid and liquid propellant systems, the boundary layer combustion process and the diffusion based mixing within a hybrid rocket grain port leaves the core flow unmixed and limits the system performance. One principle used to enhance the mixing of gaseous flows is to induce streamwise vorticity. The counter-rotating vortex pair (CVP) mixer utilizes this principle and introduces two vortices into a confined flow, generating a stirring motion in order to transport near wall media towards the core and vice versa. Recent studies investigated the velocity field introduced by this type of swirler. The current work is evaluating the mixing performance of the CVP concept, by using an experimental setup to simulate an axial primary pipe flow with a radially entering secondary flow. Hereby the primary flow is altered by the CVP swirler unit. The resulting setup therefore emulates a hybrid rocket motor with a cylindrical single port grain. In order to evaluate the mixing performance the secondary flow concentration at the pipe assembly exit is measured, utilizing a pressure-sensitive paint based procedure.

  17. Effect of the conical-shape on the performance of vortex tube

    Science.gov (United States)

    Guen, M.; Natkaniec, C.; Kammeyer, J.; Seume, J. R.; Adjlout, L.; Imine, O.

    2013-04-01

    The present study focuses on the effect of conical shape in the cold side of the Ranque-Hilsch vortex tube which is shown to have a considerable influence on the system performance. A vortex tube is a simple circular tube with no moving parts which is capable to divide a high pressure flow into two relatively lower pressure flows with temperatures higher and lower than the incoming flow. A three-dimensional computational fluid dynamic model is used to analyse the mechanisms of flow inside a vortex tube. The SST turbulence model is used to predict the turbulent flow behaviour inside the vortex tube. The geometry of a vortex tube with circumferential inlet slots as well as axial cold and hot outlet is considered. Performance curves temperature separation versus cold outlet mass fraction are calculated for a given inlet mass flow rate and varying outlet mass flow rates.

  18. Wavelet Transform Of Acoustic Signal From A Ranque- Hilsch Vortex Tube

    Science.gov (United States)

    Istihat, Y.; Wisnoe, W.

    2015-09-01

    This paper presents the frequency analysis of flow in a Ranque-Hilsch Vortex Tube (RHVT) obtained from acoustic signal using microphones in an isolated formation setup. Data Acquisition System (DAS) that incorporates Analog to Digital Converter (ADC) with laptop computer has been used to acquire the wave data. Different inlet pressures (20, 30, 40, 50 and 60 psi) are supplied and temperature differences are recorded. Frequencies produced from a RHVT are experimentally measured and analyzed by means of Wavelet Transform (WT). Morlet Wavelet is used and relation between Pressure variation, Temperature and Frequency are studied. Acoustic data has been analyzed using Matlab® and time-frequency analysis (Scalogram) is presented. Results show that the Pressure is proportional with the Frequency inside the RHVT whereby two distinct working frequencies is pronounced in between 4-8 kHz.

  19. Transformational Leadership and Team Performance

    Directory of Open Access Journals (Sweden)

    Huey-Wen Chou

    2013-07-01

    Full Text Available This study explores the relationships among transformational leadership style, cognitive trust, and collective efficacy as well as the impact of these variables on distal team performance. Data collected from 39 teams find that team cognitive trust as two process variables involves a transformational leadership process in which cognitive trust in the team leader and cognitive trust among team members mediate the impact of this leadership style on collective efficacy. Unlike previous studies, our results show that leveraging cognitive trust in the team leader is necessary but not sufficient for better proximal collective efficacy, which in turn facilitates distal team performance. Although cognitive trust among team members was more closely related to proximal collective efficacy than cognitive trust in the team leader was, the factors that foster the development of cognitive trust among team members remain scantly explored in the transformational leadership literature and deserve more attention in future research.

  20. Prediction of the Effect of Vortex Generators on Airfoil Performance

    DEFF Research Database (Denmark)

    Sørensen, Niels N.; Zahle, Frederik; Bak, Christian

    2014-01-01

    Vortex Generators (VGs) are widely used by the wind turbine industry, to control the flow over blade sections. The present work describes a computational fluid dynamic procedure that can handle a geometrical resolved VG on an airfoil section. After describing the method, it is applied to two...

  1. Effect of an external vortex on the uav aerodynamic performances

    Science.gov (United States)

    Boudaoud, Warda; Yahiaoui, Tayeb; Imine, Bachir; Imine, Omar

    2012-06-01

    In this present work, the CFD and wind tunnel are used to investigate the effect of an external vortex around an UAV in order to obtain initial estimates of lift and drag coefficients with flow velocity of 30 meters per second for various angles of attack. The model of Spalart- Allmaras turbulence is used for the investigation of the complex flow around the UAV. The wind tunnel and CFD results are compared and appropriate error bands placed on the data.

  2. Effect of an external vortex on the uav aerodynamic performances

    Directory of Open Access Journals (Sweden)

    Imine Bachir

    2012-06-01

    Full Text Available In this present work, the CFD and wind tunnel are used to investigate the effect of an external vortex around an UAV in order to obtain initial estimates of lift and drag coefficients with flow velocity of 30 meters per second for various angles of attack. The model of Spalart- Allmaras turbulence is used for the investigation of the complex flow around the UAV. The wind tunnel and CFD results are compared and appropriate error bands placed on the data.

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

    Science.gov (United States)

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

    2017-04-01

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

  4. Optimization of counter flow Ranque-Hilsch vortex tube performance using Taguchi method

    Energy Technology Data Exchange (ETDEWEB)

    Pinar, Ahmet Murat [Celal Bayar University, Vocational High School, Department of Machinery, 45400-Turgutlu-Manisa (Turkey); Uluer, Onuralp [Gazi University, Faculty of Technical Education, Mechanical Education Department, Teknikokullar, 06503 Ankara (Turkey); Kirmaci, Volkan [Bartin University, Faculty of Engineering, Mechanical Engineering Department, 74100 Bartin (Turkey)

    2009-09-15

    This study discusses the application of Taguchi method in assessing maximum temperature gradient for the Ranque-Hilsch counter flow vortex tube performance. The experiments were planned based on Taguchi's L27 orthogonal array with each trial performed under different conditions of inlet pressure, nozzle number and fluid type. Signal-to-noise ratio (S/N) analysis, analysis of variance (ANOVA) and regression analysis were carried out in order to determine the effects of process parameters and optimal factor settings. Finally, confirmation tests verified that Taguchi method achieved optimization of counter flow Ranque-Hilsch vortex tube performance with sufficient accuracy. (author)

  5. Numerical investigation of conjugate heat transfer and flow performance of a fin and tube heat exchanger with vortex generators

    DEFF Research Database (Denmark)

    Singh, Shobhana; Sørensen, Kim

    2017-01-01

    Vortex generator is considered as an effective device for augmentation of the thermal-hydraulic performance of a heat exchanger. The aim of present study is to examine the influence of vortex generators on a double fin and tube heat exchanger performance. Vortex generator of rectangular winglet...... loss characteristics are determined and analyzed for an in-line configuration of a fin and tube heat exchanger. In order to evaluate the enhancement in the performance on an equitable basis, the heat exchanger with plain fin surface is considered as a reference design. Results show that the angle...... of attack of a vortex generator has a significant impact on the volume goodness factor, and enhance the thermal performance of a fin and tube heat exchanger in comparison to the design with plain fin. The vortex generator at an angle of attack ??10 is found to perform superior over the Reynolds number range...

  6. Comparative performance tests on the Mod-2, 2.5-mW wind turbine with and without vortex generators

    Science.gov (United States)

    Miller, G. E.

    1995-01-01

    A test program was conducted on the third Mod-2 unit at Goldendale, Washington, to systematically study the effect of vortex generators (VG's) on power performance. The subject unit was first tested without VG's to obtain baseline data. Vortex generators were then installed on the mid-blade assemblies, and the resulting 70% VG configuration was tested. Finally, vortex generators were mounted on the tip assemblies, and data was recorded for the 100% VG configuration. This test program and its results are discussed in this paper. The development of vortex generators is also presented.

  7. Optimization of thermal performance of Ranque Hilsch Vortex Tube: MADM techniques

    Science.gov (United States)

    Devade, K. D.; Pise, A. T.

    2016-08-01

    Thermal performance of vortex tube is noticeably influenced by its geometrical and operational parameters. In this study effect of various geometrical (L/D ratio: 15, 16, 17, 18; exit valve angle; 300, 450, 600, 750, 900; cold end orifice diameter: 5, 6 and 7mm, tube divergence angle: 00, 20, 30, 40) and operational parameters (inlet pressure: 2 to 6 bars) on the performance of vortex tube have been investigated experimentally. Multiple Attribute Decision Making (MADM) techniques are applied to determine the optimum combination of the vortex tube. Performance of vortex tube was analysed with optimum temperature difference on cold end, COP for cooling. The MADM (Multiple Attribute Decision Making) methods, namely WSM (Weighted Sum Method), WPM (Weighted Power Method), TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) and AHP (Analytical Hierarchy Process) are applied. Experimental best performing combinations are obtained for Length to Diameter ratios 15, 16, 17 with exit valve angle as 450,750 and 900 at orifice diameter 5mm for inlet pressure of 5 and 6 bar pressure. Best COP, efficiency and cold end temperature difference are 0.245, 40.6% and 38.3K respectively for the combination of 15 L/D, 450 valve angle, 5mm orifice diameter and 2 bar pressure by MADM techniques.

  8. Modeling the cooling performance of vortex tube using a genetic algorithm-based artificial neural network

    Directory of Open Access Journals (Sweden)

    Pouraria Hassan

    2016-01-01

    Full Text Available In this study, artificial neural networks (ANNs have been used to model the effects of four important parameters consist of the ratio of the length to diameter(L/D, the ratio of the cold outlet diameter to the tube diameter(d/D, inlet pressure(P, and cold mass fraction (Y on the cooling performance of counter flow vortex tube. In this approach, experimental data have been used to train and validate the neural network model with MATLAB software. Also, genetic algorithm (GA has been used to find the optimal network architecture. In this model, temperature drop at the cold outlet has been considered as the cooling performance of the vortex tube. Based on experimental data, cooling performance of the vortex tube has been predicted by four inlet parameters (L/D, d/D, P, Y. The results of this study indicate that the genetic algorithm-based artificial neural network model is capable of predicting the cooling performance of vortex tube in a wide operating range and with satisfactory precision.

  9. Devil’s Vortex Phase Structure as Frequency Plane Mask for Image Encryption Using the Fractional Mellin Transform

    Directory of Open Access Journals (Sweden)

    Sunanda Vashisth

    2014-01-01

    Full Text Available A frequency plane phase mask based on Devil’s vortex structure has been used for image encryption using the fractional Mellin transform. The phase key for decryption is obtained by an iterative phase retrieval algorithm. The proposed scheme has been validated for grayscale secret target images, by numerical simulation. The efficacy of the scheme has been evaluated by computing mean-squared-error between the secret target image and the decrypted image. Sensitivity analysis of the decryption process to variations in various encryption parameters has been carried out. The proposed encryption scheme has been seen to exhibit reasonable robustness against occlusion attack.

  10. INFLUENCE OF TRANSFORMATIONAL LEADERSHIP ON MANAGEMENT PERFORMANCE

    Directory of Open Access Journals (Sweden)

    Mihaela TĂNASE

    2014-11-01

    Full Text Available In today's business world, competitive advantage reflects the ability of the organization to achieve high performance through proper, effective and efficient management. This paper seeks to propose a conceptual model and the companies considered for this study are chosen from Romania, specifically the multinational ones. The research tries to find what attributes of personality belonging to the components of transformational leadership are responsible for an increase or decrease of management performance. Thus, the methodology of the previous survey goes on identifying if it can establish a causal relationship type “stimulus – effect” (personality to transformational leadership, transformational leadership to management performance. The conclusions for the methodological aspects illustrate on one hand, relationship between transformational leadership and management performance and on the other hand, the profile of the effective transformational leader from multinational companies in the services sector, in the NE region of Romania.

  11. Performance augmentation with vortex generators: Design and testing for stall-regulated AWT-26 turbine

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, D.A. [Advanced Wind Turbines Inc., Seattle, WA (United States)

    1996-12-31

    A study investigated the use of vortex generators (VGs) for performance augmentation of the stall-regulated AWT-26 wind turbine. Based on wind-tunnel results and analysis, a VG array was designed for and tested on the AWT-26 prototype, designated Pt. Performance and loads data were measured for P1, both with and without VGs installed. The turbine performance with VGs met most of the design requirements; power output was increased at moderate wind speeds with a minimal effect on peak power. However, VG drag penalties caused a loss in power output for low wind speeds, such that performance with VGs resulted in a net decrease in AEP for wind speed sites up to 8.5 m/s. 8 refs., 8 figs., 3 tabs.

  12. Performance of nonsynchronous noncommensurate impedance transformers in comparison to tapered line transformers

    DEFF Research Database (Denmark)

    Kim, Kseniya; Zhurbenko, Vitaliy; Johansen, Tom Keinicke

    2012-01-01

    Nonsynchronous noncommensurate impedance transformers consist of a combination of high- and low-impedance transmission lines. The present work is dedicated to the synthesis of such transformers. They are analyzed employing wave transmission matrices. The performance of the transformer is compared...... to a traditional tapered line impedance transformer. The increase in bandwidth of nonsynchronous noncommensurate impedance transformers typically leads to shortening the transformer length, which makes the transformer attractive for applications, where a wide operating band and high transformation ratios...

  13. Vortex Counter-Current Chromatography: Performance of a New Preparative Column.

    Science.gov (United States)

    Ito, Yoichiro; Clary, Robert; Witten, Jacob J; Zeng, Yun

    2012-10-01

    A New preparative column for the vortex counter-current chromatograph was fabricated by making many (966) cylindrical separation units to a high-dendity polyethylene disk and thenthreading them with 6-40 taps. The resulting column had a total capacity of 364 mL. The performance of this vortex column was examined with three different two-phase solvent systems each using a set of suitable test samples: hexane-ethyl acetate-methanol-0.1 M hydrochloric acid (1:1:1:1, v/v) for separation of DNP-amino acids; 1-butanol-acetic acid-water (4:1:5, v/v) for separation of dipeptides; and hexane-acetonitrile-water (20:15:2, v/v) for separation of Sudan dyes. Most of the separations show high partition efficiency of over a thousand theoretical plates, as expected based on the results previously obtained in preliminary separations with a small column. Overall, the results of the present study suggest that further improvement of the partition efficiency can be obtained by the modifying column configuration.

  14. Effect of vortex generators on the power conversion performance and structural dynamic loads of the Mod-2 wind turbine

    Science.gov (United States)

    Sullivan, T. L.

    1984-01-01

    Applying vortex generators from 20 to 100 percent span of the Mod-2 rotor resulted in a projected increase in annual energy capture of 20 percent and reduced the wind speed at which rated power is reached by nearly 3 m/sec. Application of vortex generators from 20 to 70 percent span, the fixed portion of the Mod-2 rotor, resulted in a projected increase in annual energy capture of about half this. This improved performance came at the cost of a small increase in cyclic blade loads in below rated power conditions. Cyclic blade loads were found to correlate well with the change in wind speed during one rotor revolution.

  15. Evaluation of the Performance of Vortex Generators on the DU 91-W2-250 Profile using Stereoscopic PIV

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Hansen, Martin Otto Laver; Meyer, Knud Erik

    2009-01-01

    Stereoscopic PIV measurements investigating the effect of Vortex Generators on the lift force near stall and on glide ratio at best aerodynamic performance have been carried out in the LM Glasfiber wind tunnel on a DU 91-W2-250 profile. Measurements at two Reynolds numbers were analyzed; Re=0...

  16. Evaluation of the Performance of Vortex Generators on the DU 91-W2-250 Profile using Stereoscopic PIV

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Hansen, Martin Otto Laver; Meyer, Knud Erik

    2008-01-01

    Stereoscopic PIV measurements investigating the effect of Vortex Generators on the lift force near stall and on glide ratio at best aerodynamic performance have been carried out in the LM Glasfiber wind tunnel on a DU 91-W2-250 profile. Measurements at two Reynolds numbers were analyzed; Re=0...

  17. Development of a High-Performance Fin-and-Tube Heat Exchanger with Vortex Generators for a Vending Machine

    Science.gov (United States)

    Iwasaki, Masamichi; Saito, Hiroshi; Mochizuki, Sadanari; Murata, Akira

    The effect of delta-wing-vortex generators (combination of a delta wing and a delta winglet pair) on the heat transfer performance of fin-and-tube heat exchangers for vending machines has been investegated. Flow visualizations, numerical simulations and heat transfer experiments were conducted to find an optimum geometrical shape and arrangement of the vortex generators. Maximum heat transfer enhancement was achieved by the combination of (a) the delta wing with the apex angle of 86 degrees and (b) the delta winglet pair with the inline angle of 45 degrees. In relatively low Reynolds number range, about 40 % increase in heat transfer coefficient was attained with the above mentioned combination of the vortex generators compared to the ordinary heat exchangers with plain fins. It was revealed that the heat transfer enhancement was attributed to (1) the longitudinal vortexes generated by the delta wing and (2) the reduction of wake area behind the tube. It was also found that an increase in the apex angle of the delta wing brought about heat transfer enhancement, and the scale as well as the streggth of the induced longitudinal vortices played an important role in the heat transfer performance.

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

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, L. A., E-mail: smirnov-lev@allp.sci-nnov.ru; Smirnov, A. I., E-mail: smirnov@appl.sci-nnov.ru; Mironov, V. A. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

    2016-01-15

    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 to 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).

  19. Numerical investigation of conjugate heat transfer and flow performance of a fin and tube heat exchanger with vortex generators

    DEFF Research Database (Denmark)

    Singh, Shobhana; Sørensen, Kim

    2017-01-01

    type is chosen and investigated at different angles of attack 0 , ??10 and ??20 with the flow direction. Three-dimensional numerical model is developed and simulations are performed for a Reynolds number range 5000 Re 11000 taking conjugate heat transfer into account. The heat transfer and pressure...... loss characteristics are determined and analyzed for an in-line configuration of a fin and tube heat exchanger. In order to evaluate the enhancement in the performance on an equitable basis, the heat exchanger with plain fin surface is considered as a reference design. Results show that the angle...... of attack of a vortex generator has a significant impact on the volume goodness factor, and enhance the thermal performance of a fin and tube heat exchanger in comparison to the design with plain fin. The vortex generator at an angle of attack ??10 is found to perform superior over the Reynolds number range...

  20. Effect of Intake Vortex Occurrence on the Performance of an Axial Hydraulic Turbine in Sihwa-Lake Tidal Power Plant, Korea

    National Research Council Canada - National Science Library

    Kim, Jin-Hyuk; Heo, Man-Woong; Cha, Kyung-Hun; Kim, Kwang-Yong; Tac, Se-Wyan; Cho, Yong; Hwang, Jae-Chun; Collins, Maria

    2012-01-01

    A numerical study to investigate the effect of intake vortex occurrence on the performance of an axial hydraulic turbine for generating tidal power energy in Sihwa-lake tidal power plant, Korea, is performed...

  1. Rapid Estimation of Aircraft Performance Models using Differential Vortex Panel Method and Extended Kalman Filter Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Estimation of aerodynamic models for the control of damaged aircraft using an innovative differential vortex lattice method tightly coupled with an extended Kalman...

  2. Rapid Estimation of Aircraft Performance Models using Differential Vortex Panel Method and Extended Kalman Filter Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The problem of estimating the aerodynamic models for flight control of damaged aircraft using an innovative differential vortex lattice method tightly coupled with...

  3. On-sky performance of the QACITS pointing control technique with the Keck/NIRC2 vortex coronagraph

    Science.gov (United States)

    Huby, E.; Bottom, M.; Femenia, B.; Ngo, H.; Mawet, D.; Serabyn, E.; Absil, O.

    2017-04-01

    Context. A vortex coronagraph is now available for high contrast observations with the Keck/NIRC2 instrument at L band. The vortex coronagraph uses a vortex phase mask in a focal plane and a Lyot stop in a downstream pupil plane to provide high contrast at small angular separations from the observed host star. Aims: Reaching the optimal performance of the coronagraph requires fine control of the wavefront incident on the phase mask. In particular, centering errors can lead to significant stellar light leakage that degrades the contrast performance and prevents the observation of faint planetary companions around the observed stars. It is thus critical to correct for the possible slow drift of the star image from the phase mask center, generally due to mechanical flexures induced by temperature and/or gravity field variation, or to misalignment between the optics that rotate in pupil tracking mode. Methods: A control loop based on the QACITS algorithm for the vortex coronagraph has been developed and deployed for the Keck/NIRC2 instrument. This algorithm executes the entire observing sequence, including the calibration steps, initial centering of the star on the vortex center, and stabilisation during the acquisition of science frames. Results: On-sky data show that the QACITS control loop stabilizes the position of the star image down to 2.4 mas rms at a frequency of about 0.02 Hz. However, the accuracy of the estimator is probably limited by a systematic error due to a misalignment of the Lyot stop with respect to the entrance pupil, estimated to be on the order of 4.5 mas. A method to reduce the amplitude of this bias down to 1 mas is proposed. Conclusions: The QACITS control loop has been successfully implemented and provides a robust method to center and stabilize the star image on the vortex mask. In addition, QACITS ensures a repeatable pointing quality and significantly improves the observing efficiency compared to manual operations. It is now routinely used

  4. Impact of Transformational Leadership on Job Performance

    Directory of Open Access Journals (Sweden)

    Jeevan Jyoti

    2015-11-01

    Full Text Available The present study focuses on the role of leader–member exchange and relational identification (RI between transformational leadership and job performance relationship. The model has been tested in higher education sector. All the permanent teachers working in higher education sector were contacted. The data have been duly validated with the help of confirmatory factor analysis (CFA. Reliability has been assessed through Cronbach’s alpha and composite reliability. Structural equation modeling (SEM has been used for hypotheses testing, and hierarchical regression has been used to test the moderating effect of RI. The results indicated that leader–member exchange acts as a mediator and RI acts as a moderator instead of mediator. The managerial implications and future scope have been discussed.

  5. Performance Comparison and Selection of Transformer Fluid

    Directory of Open Access Journals (Sweden)

    Lu Yang

    2016-01-01

    Full Text Available Transformer fluid directly affects the working state of the components and the cooling efficiency of transformer. There are three kinds of transformer fluid used for electric locomotive, EMU and suburban rail vehicles: mineral oil, silicone liquid and synthetic ester based insulating oil. In this paper, the three kinds of oil are compared from the fire safety, environmental protection, reliability and low maintenance. It provides a strong basis for the selection of transformer fluid. By comprehensive analysis, synthetic ester based insulating oil can completely replace mineral oil and silicone liquid. With rail transport safety and environmental protection standards improving, synthetic ester based insulating oil will be the best choice for transformer.

  6. Aerodynamically shaped vortex generators

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver; Velte, Clara Marika; Øye, Stig

    2016-01-01

    An aerodynamically shaped vortex generator has been proposed, manufactured and tested in a wind tunnel. The effect on the overall performance when applied on a thick airfoil is an increased lift to drag ratio compared with standard vortex generators. Copyright © 2015 John Wiley & Sons, Ltd....

  7. 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 HPLC.

    Science.gov (United States)

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

    2017-10-25

    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 (S/N = 3) of the method ranged from 1.0 to 4.6 μg·L(-1) , 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 recoveries rate for three analytes (fumaric acid was undetected) range from 82.0 to 110.6%. 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. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  8. Uncovering the relationship between transformational leaders and followers' task performance.

    NARCIS (Netherlands)

    Breevaart, K.; Bakker, A. B.; Demerouti, E.; Sleebos, D. M.; Maduro, V.

    2015-01-01

    The purpose of the present study was to unravel the mechanisms underlying the relationship between transformational leadership, follower work engagement, and follower job performance and to investigate a possible boundary condition of transformational leadership. We used structural equation modeling

  9. Experimental study of vortex diffusers

    Energy Technology Data Exchange (ETDEWEB)

    Shakerin, S.; Miller, P.L. [National Renewable Energy Lab., Golden, CO (United States)

    1995-11-01

    This report documents experimental research performed on vortex diffusers used in ventilation and air-conditioning systems. The main objectives of the research were (1) to study the flow characteristics of isothermal jets issuing from vortex diffusers, (2) to compare the vortex diffuser`s performance with that of a conventional diffuser, and (3) to prepare a report that disseminates the results to the designers of ventilation and air-conditioning systems. The researchers considered three diffusers: a conventional round ceiling diffuser and two different styles of vortex diffusers. Overall, the vortex diffusers create slightly more induction of ambient air in comparison to the conventional diffuser.

  10. Enhancement of Energy Harvesting Performance by a Coupled Bluff Splitter Body and PVEH Plate through Vortex Induced Vibration near Resonance

    Directory of Open Access Journals (Sweden)

    Wei Ken Chin

    2017-09-01

    Full Text Available Inspired by vortex induced vibration energy harvesting development as a new source of renewable energy, a T-shaped design vibration energy harvester is introduced with the aim of enhancing its performance through vortex induced vibration at near resonance conditions. The T-shaped structural model designed consists of a fixed boundary aluminum bluff splitter body coupled with a cantilever piezoelectric vibration energy harvesters (PVEH plate model which is a piezoelectric bimorph plate made of a brass plate sandwiched between 2 lead zirconate titanate (PZT plates. A 3-dimensional Fluid-Structure Interaction simulation analysis is carried out with Reynolds Stress Turbulence Model under wind speed of 7, 10, 12, 14, 16, 18, 19, 20, 22.5, and 25 m/s. The results showed that with 19 m/s wind speed, the model generates 75.758 Hz of vortex frequency near to the structural model’s natural frequency of 76.9 Hz. Resonance lock-in therefore occurred, generating a maximum displacement amplitude of 2.09 mm or a 49.76% increment relatively in vibrational amplitude. Under the effect of resonance at the PVEH plate’s fundamental natural frequency, it is able to generate the largest normalized power of 13.44 mW/cm3g2.

  11. Performance in model transformations: experiments with ATL and QVT

    NARCIS (Netherlands)

    van Amstel, Marcel; Bosems, S.; Ivanov, Ivan; Ferreira Pires, Luis; Cabot, Jordi; Visser, Eelco

    Model transformations are increasingly being incorporated in software development processes. However, as systems being developed with transformations grow in size and complexity, the performance of the transformations tends to degrade. In this paper we investigate the factors that have an impact on

  12. Optical vortex metrology based on the core structures of phase singularities in Laguerre-Gauss transform of a speckle pattern.

    Science.gov (United States)

    Wang, Wei; Yokozeki, Tomoaki; Ishijima, Reika; Takeda, Mitsuo; Hanson, Steen G

    2006-10-30

    A new technique for displacement measurement is proposed that makes use of phase singularities in the complex signal generated by a Laguerre-Gauss filter operation applied to a speckle pattern. The core structures of phase singularities are used as unique fingerprints attached to the object surface, and the displacement is determined by tracing the movement of registered phase singularities with their correspondence being identified by the fingerprints. Experimental results for translational and rotational displacement measurements are presented that demonstrate large dynamic range and high spatial resolution of the proposed optical vortex metrology.

  13. Effect of Mach number, valve angle and length to diameter ratio on thermal performance in flow of air through Ranque Hilsch vortex tube

    Science.gov (United States)

    Devade, Kiran D.; Pise, Ashok T.

    2017-01-01

    Ranque Hilsch vortex tube is a device that can produce cold and hot air streams simultaneously from pressurized air. Performance of vortex tube is influenced by a number of geometrical and operational parameters. In this study parametric analysis of vortex tube is carried out. Air is used as the working fluid and geometrical parameters like length to diameter ratio (15, 16, 17, 18), exit valve angles (30°-90°), orifice diameters (5, 6 and 7 mm), 2 entry nozzles and tube divergence angle 4° is used for experimentation. Operational parameters like pressure (200-600 kPa), cold mass fraction (0-1) is varied and effect of Mach number at the inlet of the tube is investigated. The vortex tube is tested at sub sonic (0 tube is observed for CMF up to 0.5. Experimental correlations are proposed for optimum COP. Parametric correlation is developed for geometrical and operational parameters.

  14. Evolution of optical vortex distributions in stochastic vortex fields

    Science.gov (United States)

    Roux, Filippus S.

    2011-03-01

    Stochastic vortex fields are found in laser speckle, in scintillated beams propagating through a turbulent atmosphere, in images of holograms produced by Iterative Fourier Transform methods and in the beams produced by certain diffractive optical elements, to name but a few. Apart from the vortex fields found in laser speckle, the properties and dynamics of stochastic vortex fields are largely unexplored. Stochastic vortex fields with non-equilibrium initial conditions exhibit a surprisingly rich phenomenology in their subsequent evolution during free-space propagation. Currently there does not exist a general theory that can predict this behavior and only limited progress has thus far been made in its understanding. Curves of the evolution of optical vortex distributions during free-space propagation that are obtained from numerical simulations, will be presented. A variety of different stochastic vortex fields are used as input to these simulations, including vortex fields that are homogeneous in their vortex distributions, as well as inhomogeneous vortex fields where, for example, the topological charge densities vary sinusoidally along one or two dimensions. Some aspects of the dynamics of stochastic vortex fields have been uncovered with the aid of these numerical simulations. For example, the numerical results demonstrate that stochastic vortex fields contain both diffusion and drift motions that are driven by local and global variations in amplitude and phase. The mechanisms for these will be explained. The results also provide evidence that global variations in amplitude and phase are caused by variations in the vortex distributions, giving rise to feedback mechanisms and nonlinear behavior.

  15. The effect of shape of winglet vortex generator on the thermal-hydrodynamic performance of a circular tube bank fin heat exchanger

    Science.gov (United States)

    Hu, Wanling; Wang, Liangbi; Guan, Yong; Hu, Wenju

    2017-09-01

    In real application, the shape of the vortex generator has great influence on the heat transfer and flow resistance characteristics of tube bank fin heat exchanger. Therefore, the effect of the shape of the vortex generator on heat transfer performance of such heat exchanger should be considered. In this paper, the effect of three different shaped vortex generators (i.e. delta winglet, rectangular winglet and trapezoid winglet) on heat transfer intensity and secondary flow intensity of a circular tube bank fin heat exchanger was numerically studied. The results show that with increasing Re, overall average Nu and the non-dimensional secondary flow intensity Se m increase however friction factor f decreases. A corresponding relationship can be found between Nu and Se m, which indicates that the secondary flow intensity determines the heat transfer intensity in the fin-side channel of circular tube bank fin heat exchanger with different shaped vortex generators on the fin surfaces. Under the identical pumping power constrain, the optimal shape of the vortex generators is the delta winglet vortex generators for the studied cases.

  16. An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

    Directory of Open Access Journals (Sweden)

    Xuanlin Peng

    2017-11-01

    Full Text Available In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration based on field experiments and a finite element method (FEM is presented. It is found that the resonance between the Kármán vortex and the stay vane is the main cause for the undesired vibration. Then, we focus on establishing an intelligent optimization model of the stay vane’s trailing edge profile. To this end, an approach combining factorial experiments, extreme learning machine (ELM and particle swarm optimization (PSO is implemented. Three kinds of improved profiles of the stay vane are proposed and compared. Finally, the profile with a Donaldson trailing edge is adopted as the best solution for the stay vane, and verifications such as computational fluid dynamics (CFD simulations, structural analysis and fatigue analysis are performed to validate the optimized geometry.

  17. Improving the cooling performance of electrical distribution transformer using transformer oil – Based MEPCM suspension

    Directory of Open Access Journals (Sweden)

    Mushtaq Ismael Hasan

    2017-04-01

    Full Text Available In this paper the electrical distribution transformer has been studied numerically and the effect of outside temperature on its cooling performance has been investigated. The temperature range studied covers the hot climate regions. 250 KVA distribution transformer is chosen as a study model. A novel cooling fluid is proposed to improve the cooling performance of this transformer, transformer oil-based microencapsulated phase change materials suspension is used with volume concentration (5–25% as a cooling fluid instead of pure transformer oil. Paraffin wax is used as a phase change material to make the suspension, in addition to the ability of heat absorption due to melting, the paraffin wax considered as a good electrical insulator. Results obtained show that, using of MEPCM suspension instead of pure transformer oil lead to improve the cooling performance of transformer by reducing its temperature and as a consequence increasing its protection against the breakdown. The melting fraction increased with increasing outside temperature up to certain temperature after which the melting fraction reach maximum constant value (MF = 1 which indicate that, the choosing of PCM depend on the environment in which the transformer is used.

  18. Relationship of Transformational Leadership, Organizational Learning and Organizational Performance

    National Research Council Canada - National Science Library

    Amena Y Mutahar; Amran Md Rasli; Basheer M Al-Ghazali

    2015-01-01

      Purpose of this study is to analyze the influence of transformational leadership on organizational performance through the dynamic capabilities of organizational learning in telecom sector of Kingdom of Saudi Arabia (KSA...

  19. Predicting unit performance by assessing transformational and transactional leadership.

    Science.gov (United States)

    Bass, Bernard M; Avolio, Bruce J; Jung, Dong I; Berson, Yair

    2003-04-01

    How do leadership ratings collected from units operating under stable conditions predict subsequent performance of those units operating under high stress and uncertainty? To examine this question, the authors calculated the predictive relationships for the transformational and transactional leadership of 72 light infantry rifle platoon leaders for ratings of unit potency, cohesion, and performance for U.S. Army platoons participating in combat simulation exercises. Both transformational and transactional contingent reward leadership ratings of platoon leaders and sergeants positively predicted unit performance. The relationship of platoon leadership to performance was partially mediated through the unit's level of potency and cohesion. Implications, limitations, and future directions for leadership research are discussed.

  20. Experimental investigation of the performance of a Ranque-Hilsch vortex tube with regard to a plug located at the hot outlet

    Energy Technology Data Exchange (ETDEWEB)

    Dincer, K. [Department of Mechanical Engineering, Faculty of Engineering and Architecture, Selcuk University, Konya (Turkey); Baskaya, S. [Department of Mechanical Engineering, Faculty of Engineering and Architecture, Gazi University, Maltepe, 06570 Ankara (Turkey); Uysal, B.Z. [Department of Chemical Engineering, Faculty of Engineering and Architecture, Gazi University, Maltepe, Ankara (Turkey); Ucgul, I. [Department of Textile Engineering, Faculty of Engineering and Architecture, Suleyman Demirel University, Isparta (Turkey)

    2009-01-15

    In this study, effects of position, diameter (5, 6, 7, 8 mm) and angle (30 -180 ) of a mobile plug, located at the hot outlet side in a Ranque-Hilsch Vortex Tube (RHVT), were determined experimentally for best performance. In addition to plug parameters, effects of supply pressure (200-420 kPa) and number of nozzles (2, 4, 6) were also studied. The internal diameter (D) of the vortex tube used in the experiments was 9 mm; the ratio of the length of the vortex tube to its diameter (L/D) was 15. Four different plug locations were studied. The maximum difference in the temperatures of hot and cold streams was obtained for the plug diameter of 5 mm, tip angles of 30 and 60 , 4 nozzles and by keeping the plug location at the far extreme end. (author)

  1. Vortex wake, downwash distribution, aerodynamic performance and wingbeat kinematics in slow-flying pied flycatchers

    Science.gov (United States)

    Muijres, Florian T.; Bowlin, Melissa S.; Johansson, L. Christoffer; Hedenström, Anders

    2012-01-01

    Many small passerines regularly fly slowly when catching prey, flying in cluttered environments or landing on a perch or nest. While flying slowly, passerines generate most of the flight forces during the downstroke, and have a ‘feathered upstroke’ during which they make their wing inactive by retracting it close to the body and by spreading the primary wing feathers. How this flight mode relates aerodynamically to the cruising flight and so-called ‘normal hovering’ as used in hummingbirds is not yet known. Here, we present time-resolved fluid dynamics data in combination with wingbeat kinematics data for three pied flycatchers flying across a range of speeds from near hovering to their calculated minimum power speed. Flycatchers are adapted to low speed flight, which they habitually use when catching insects on the wing. From the wake dynamics data, we constructed average wingbeat wakes and determined the time-resolved flight forces, the time-resolved downwash distributions and the resulting lift-to-drag ratios, span efficiencies and flap efficiencies. During the downstroke, slow-flying flycatchers generate a single-vortex loop wake, which is much more similar to that generated by birds at cruising flight speeds than it is to the double loop vortex wake in hovering hummingbirds. This wake structure results in a relatively high downwash behind the body, which can be explained by the relatively active tail in flycatchers. As a result of this, slow-flying flycatchers have a span efficiency which is similar to that of the birds in cruising flight and which can be assumed to be higher than in hovering hummingbirds. During the upstroke, the wings of slowly flying flycatchers generated no significant forces, but the body–tail configuration added 23 per cent to weight support. This is strikingly similar to the 25 per cent weight support generated by the wing upstroke in hovering hummingbirds. Thus, for slow-flying passerines, the upstroke cannot be regarded as

  2. Vortex wake, downwash distribution, aerodynamic performance and wingbeat kinematics in slow-flying pied flycatchers.

    Science.gov (United States)

    Muijres, Florian T; Bowlin, Melissa S; Johansson, L Christoffer; Hedenström, Anders

    2012-02-07

    Many small passerines regularly fly slowly when catching prey, flying in cluttered environments or landing on a perch or nest. While flying slowly, passerines generate most of the flight forces during the downstroke, and have a 'feathered upstroke' during which they make their wing inactive by retracting it close to the body and by spreading the primary wing feathers. How this flight mode relates aerodynamically to the cruising flight and so-called 'normal hovering' as used in hummingbirds is not yet known. Here, we present time-resolved fluid dynamics data in combination with wingbeat kinematics data for three pied flycatchers flying across a range of speeds from near hovering to their calculated minimum power speed. Flycatchers are adapted to low speed flight, which they habitually use when catching insects on the wing. From the wake dynamics data, we constructed average wingbeat wakes and determined the time-resolved flight forces, the time-resolved downwash distributions and the resulting lift-to-drag ratios, span efficiencies and flap efficiencies. During the downstroke, slow-flying flycatchers generate a single-vortex loop wake, which is much more similar to that generated by birds at cruising flight speeds than it is to the double loop vortex wake in hovering hummingbirds. This wake structure results in a relatively high downwash behind the body, which can be explained by the relatively active tail in flycatchers. As a result of this, slow-flying flycatchers have a span efficiency which is similar to that of the birds in cruising flight and which can be assumed to be higher than in hovering hummingbirds. During the upstroke, the wings of slowly flying flycatchers generated no significant forces, but the body-tail configuration added 23 per cent to weight support. This is strikingly similar to the 25 per cent weight support generated by the wing upstroke in hovering hummingbirds. Thus, for slow-flying passerines, the upstroke cannot be regarded as inactive

  3. Comparison of maintenance scheme effects on power transformer reliability performance

    Directory of Open Access Journals (Sweden)

    I. C. Durán

    2015-11-01

    Full Text Available Power transformer failures have a significant impact on electrical systems reliability, as they compromise the electricity delivery. Failures impact the operational cost of electric utilities as they endanger the accomplishment of power commitments. Power transformer failure rate can be modeled from its health condition, which is determined from different condition parameters. This paper is aimed to compare different maintenance schemes that allow the asset to be available the longest possible time. The power transformer operation is represented considering actual electric load profiles and temperature. Electrical and thermal transformer parameters are taken from manufacturer tests and technical standards. An electrical-thermal model is employed to estimate the life span reduction and temperature changes. From life span and loading, the health condition is determined, so as the effects of different maintenance schemes. The failure rates are calculated for unmaintained conditions and different maintained schemes, allowing to determine their effects on transformer reliability. Optimal maintenance schemes are determined and the expected benefits in failure rate reduction, asset reliability and life span extension are presented. As a result, it was found that certain time-based maintenance schemes provide better transformer reliability performance in comparison to condition based schemes, allowing to reduce the interruptions and extending the life of the transformer.

  4. Experimental investigation of the effects of length to diameter ratio and nozzle number on the performance of counter flow Ranque-Hilsch vortex tubes

    Science.gov (United States)

    Dincer, K.; Baskaya, S.; Uysal, B. Z.

    2008-01-01

    In this experimental study, performance of counter flow type Ranque-Hilsch vortex tubes (RHVT), with a length to diameter ratio of 10, 15 and 18, were investigated with 2, 4, 6 nozzles. The measure of performance was chosen as the difference between the temperatures of hot output stream and cold output stream. The performances of RHVTs were experimentally tested by making use of velocity and temperature measurements of the input and output streams. It was determined that the difference between the temperatures of these streams, changed between 9 and 56 K. When all the results were assessed, it was concluded that the best performance was obtained when the ratio of vortex tube’s length to the diameter was 15 and the nozzle number was at least four, and the inlet pressure was as high as possible. Desired performance could be obtained by controlling the rate of the hot output stream.

  5. Experimental investigation of the effects of length to diameter ratio and nozzle number on the performance of counter flow Ranque-Hilsch vortex tubes

    Energy Technology Data Exchange (ETDEWEB)

    Dincer, K. [Selcuk University, Department of Mechanical Engineering, Faculty of Engineering and Architecture, Konya (Turkey); Baskaya, S. [Gazi University, Department of Mechanical Engineering, Faculty of Engineering and Architecture, Maltepe, Ankara (Turkey); Uysal, B.Z. [Gazi University, Department of Chemical Engineering, Faculty of Engineering and Architecture, Maltepe, Ankara (Turkey)

    2008-01-15

    In this experimental study, performance of counter flow type Ranque-Hilsch vortex tubes (RHVT), with a length to diameter ratio of 10, 15 and 18, were investigated with 2, 4, 6 nozzles. The measure of performance was chosen as the difference between the temperatures of hot output stream and cold output stream. The performances of RHVTs were experimentally tested by making use of velocity and temperature measurements of the input and output streams. It was determined that the difference between the temperatures of these streams, changed between 9 and 56 K. When all the results were assessed, it was concluded that the best performance was obtained when the ratio of vortex tube's length to the diameter was 15 and the nozzle number was at least four, and the inlet pressure was as high as possible. Desired performance could be obtained by controlling the rate of the hot output stream. (orig.)

  6. Vortex tube optimization theory

    Energy Technology Data Exchange (ETDEWEB)

    Lewins, Jeffery [Cambridge Univ., Magdalene Coll., Cambridge (United Kingdom); Bejan, Adrian [Duke Univ., Dept. of Mechanical Engineering and Materials Science, Durham, NC (United States)

    1999-11-01

    The Ranque-Hilsch vortex tube splits a single high pressure stream of gas into cold and warm streams. Simple models for the vortex tube combined with regenerative precooling are given from which an optimisation can be undertaken. Two such optimisations are needed: the first shows that at any given cut or fraction of the cold stream, the best refrigerative load, allowing for the temperature lift, is nearly half the maximum loading that would result in no lift. The second optimisation shows that the optimum cut is an equal division of the vortex streams between hot and cold. Bounds are obtainable within this theory for the performance of the system for a given gas and pressure ratio. (Author)

  7. Performance Comparison of Image Transforms for Palm Print Recognition with Fractional Coefficients of Transformed Palm Print Images

    OpenAIRE

    Dr. H. B. Kekre,; Sudeep D. Thepade,; Ashish Varun,; Nikhil Kamat,; Arvind Viswanathan; Pratik Dhwoj

    2010-01-01

    The paper presents performance comparison of palm print recognition techniques based on fractional coefficients of transformed palm print image using six different transforms like Sine, Cosine, Walsh, Slant,Hartley and Haar. In transform domain, the energy of image gets accumulated towards high frequency region; this characteristic of image transforms is exploited here to reduce the feature vector size of palm print images by neglecting the low frequency coefficients in transformed palm print...

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

    Science.gov (United States)

    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 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.

  9. Transformational leadership, work satisfaction and group performance: Mediation analysis

    OpenAIRE

    Procházka Jakub; Vaculík Martin; Smutný Petr

    2017-01-01

    This study investigated whether followers’ work satisfaction mediates the relationship between a transformational leadership style and group performance. An evaluation of 32 CEOs by 500 subordinates took place after three months of intensive cooperation within a managerial simulation game. All of the respondents were college students. The followers assessed their work satisfaction using three questions from the Job Diagnostic Survey. Each CEO was evaluated by an average of 15 followers in ter...

  10. On the vortex ring state

    Science.gov (United States)

    Green, Richard; Gillies, E.; Giuni, M.; Hislop, J.; Savas, Omer

    2014-11-01

    The investigation considers the vortex ring state, a phenomenon normally associated with the collapse of a trailing, helical vortex wake into a unstable vortex ring, and is a problem encountered when a helicopter rotor descends into its own wake. A series of wind tunnel and towing tank experiments on rotor systems have been performed, and a comparison is then made with the behaviour of a specially designed open core, annular jet system that generates a mean flow velocity profile similar to that observed below a rotor. In experimentally simulated descents the jet system forms flow patterns that are topologically similar to the vortex ring state of a rotor system. Furthermore the dynamic behaviour of the flow shares many of the important characteristics of the rotor flow. This result suggests that the phenomenon of the vortex ring state of a rotor wake is decoupled from the detailed vortex dynamics of the helical vortex filaments themselves. The presentation will describe the principle behind the investigation, the details of the annular jet system and the results gained using PIV and flow visualisation of the wake and jet systems.

  11. Improving Vortex Generators to Enhance the Performance of Air-Cooled Condensers in a Geothermal Power Plant

    Energy Technology Data Exchange (ETDEWEB)

    Manohar S. Sohal

    2005-09-01

    Colburn j-factor) associated with deployment of the winglets with circular as well as oval tubes. In general, toe-in (common flow up) type winglets appear to have better performance than the toe-out (common flow down) type winglets. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. During the course of their independent research, all of the researchers have established that about 10 to 30% enhancement in Colburn j-factor is expected. However, actual increase in heat transfer rate from a heat exchanger employing finned tubes with winglets may be smaller, perhaps on the order of 2 to 5%. It is also concluded that for any specific application, more full-size experimentation is needed to optimize the winglet design for a specific heat exchanger application. If in place of a circular tube, an oval tube can be economically used in a bundle, it is expected that the pressure drop across the tube bundle with the application of vortex generators (winglets) will be similar to that in a conventional circular tube bundle. It is hoped that the results of this research will demonstrate the benefits of applying vortex generators (winglets) on the fins to improve the heat transfer from the air-side of the tube bundle.

  12. The Impact of Transformational Leadership on Employee Sustainable Performance: The Mediating Role of Organizational Citizenship Behavior

    OpenAIRE

    Weiping Jiang; Xianbo Zhao; Jiongbin Ni

    2017-01-01

    Transformational leadership has drawn extensive attention in management research. In this field, the influence of transformational leadership on employee performance is an important branch. Recent research indicates that organizational citizenship behavior plays a mediating role between transformational leadership and employee performance. However, some of these findings contradict each other. Given the background where greater attention is being paid to transformational leadership in the con...

  13. Analytical model of the optical vortex microscope.

    Science.gov (United States)

    Płocinniczak, Łukasz; Popiołek-Masajada, Agnieszka; Masajada, Jan; Szatkowski, Mateusz

    2016-04-20

    This paper presents an analytical model of the optical vortex scanning microscope. In this microscope the Gaussian beam with an embedded optical vortex is focused into the sample plane. Additionally, the optical vortex can be moved inside the beam, which allows fine scanning of the sample. We provide an analytical solution of the whole path of the beam in the system (within paraxial approximation)-from the vortex lens to the observation plane situated on the CCD camera. The calculations are performed step by step from one optical element to the next. We show that at each step, the expression for light complex amplitude has the same form with only four coefficients modified. We also derive a simple expression for the vortex trajectory of small vortex displacements.

  14. Effects of surface anisotropy on magnetic vortex core

    Energy Technology Data Exchange (ETDEWEB)

    Pylypovskyi, Oleksandr V., E-mail: engraver@univ.net.ua [Taras Shevchenko National University of Kiev, 01601 Kiev (Ukraine); Sheka, Denis D. [Taras Shevchenko National University of Kiev, 01601 Kiev (Ukraine); Kravchuk, Volodymyr P.; Gaididei, Yuri [Institute for Theoretical Physics, 03143 Kiev (Ukraine)

    2014-06-01

    The vortex core shape in the three dimensional Heisenberg magnet is essentially influenced by a surface anisotropy. We predict that depending of the surface anisotropy type there appears barrel- or pillow-shaped deformation of the vortex core along the magnet thickness. Our theoretical study is well confirmed by spin–lattice simulations. - Highlights: • The shape of magnetic vortex core is essentially influenced by SA (surface anisotropy). • We predict barrel- or pillow-shaped deformation of the vortex depending on SA. • The variational approach fully describes the vortex core deformation. • We performed spin–lattice simulations to detect SA influence on the vortex core.

  15. Theorizing Slum Tourism: Performing, Negotiating and Transforming Inequality

    Directory of Open Access Journals (Sweden)

    Eveline Dürr

    2012-10-01

    Full Text Available Abstract:This Exploration focuses on the emerging field of slum tourism research, which has the potential to connect Latin American and Caribbean studies on tourism and urban inequality. Slum tourism involves transforming poverty, squalor and violence into a tourism product. Drawing on both altruism and voyeurism, this form of tourism is a complex phenomenon that raises various questions concerning power, inequality and subjectivity. This essay seeks to advance the theoretical debate on slum tourism research and to stimulate comparative studies. Introducing brief examples of slum tourism in Mexico and Jamaica, this contribution moves towards an initial theorization of the performance, negotiation and transformation of inequality in a framework of tourism and global mobilities.Resumen: Teorizar el Turismo en las zonas marginadas: Construcción, negociación y transformación de la desigualdadEsta Exploración se centra en el campo emergente del turismo en zonas marginadas, que tiene como potencial conectar a América Latina y el Caribe en los estudios sobre el turismo y la desigualdad urbana. Turismo 'Slum' implica la transformación de la pobreza, la miseria y la violencia en un producto turístico. Basándose tanto en el altruismo como en el voyerismo, esta forma de turismo es un fenómeno complejo que plantea diversas cuestiones relativas al poder, la desigualdad y la subjetividad. Con este ensayo se pretende avanzar en el debate teórico sobre la investigación de turismo en zonas marginadas y estimular estudios comparativos. Presentando ejemplos breves de turismo en barrios pobres en la ciudad de México y de Jamaica, esta contribución se mueve hacia una teorización inicial de la construcción, la negociación y la transformación de la desigualdad en el marco del turismo y la movilidad global.

  16. Speciation analysis of mercury in sediments using vortex-assisted liquid-liquid microextraction coupled to high-performance liquid chromatography-cold vapor atomic fluorescence spectrometry.

    Science.gov (United States)

    Leng, Geng; Yin, Hui; Li, Shaobo; Chen, Yong; Dan, Dezhong

    2012-09-15

    A simple and fast solvent microextraction method termed vortex-assisted liquid-liquid microextraction (VALLME) coupled with high-performance liquid chromatography-vapor generation atomic fluorescence spectrometry (HPLC-CVAFS) has been developed for the trace analysis of methylmercury (MeHg(+)), ethylmercury (EtHg(+)) and inorganic mercury (Hg(2+)) in sediment samples. Carbon tetrachloride was used as collecting solvent for the extraction of mercury species from sediment by a vortex-assisted extraction. In VALLME, 100 μL 1% (m/v) l-Cysteine were used as extraction solvent and were injected into 4 mL carbon tetrachloride. The extraction solvent dispersed into carbon tetrachloride under vigorously shaking by a vortex agitator. The fine droplets could extract mercury species within few minutes because of the shorter diffusion distance and larger specific surface area. After centrifugation, the floating extractant phase restored its initial single microdrop shape and was used for HPLC-CVAFS analysis. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition etc. were investigated. Under the optimum conditions, linearity was found in the concentration range from 0.1 to 25 ng g(-1) for MeHg(+), 0.2 to 65 ng g(-1) for EtHg(+), and 0.1 to 30 ng g(-1) for Hg(2+). Coefficients of determination (R(2)) ranged from 0.9938 to 0.9972. The limits of detection (LODs, signal-to-noise ratio (S/N)=3) were 0.028 ng g(-1) for MeHg(+), 0.057 ng g(-1) for EtHg(+), and 0.029 ng g(-1) for Hg(2+). Reproducibility and recoveries were assessed by testing a series of 6 sediment samples, which were spiked with different concentration levels. Finally, the proposed method was successfully applied in analyses of real nature sediment samples. In this work, VALLME was applied to the extraction of mercury species in sediment samples for the first time. Using l-Cys as extraction solvent, the

  17. Novel Vortex Generator and Mode Converter for Electron Beams

    OpenAIRE

    Schattschneider, P.; Stoeger-Pollach, M.; Verbeeck, J.

    2012-01-01

    Abstract: A mode converter for electron vortex beams is described. Numerical simulations, confirmed by experiment, show that the converter transforms a vortex beam with a topological charge m = +/- 1 into beams closely resembling Hermite-Gaussian HG(10) and HG(01) modes. The converter can be used as a mode discriminator or filter for electron vortex beams. Combining the converter with a phase plate turns a plane wave into modes with topological charge m = +/- 1. This combination serves as a g...

  18. Exergy analysis and performance of a counter flow Ranque-Hilsch vortex tube having various nozzle numbers at different inlet pressures of oxygen and air

    Energy Technology Data Exchange (ETDEWEB)

    Kirmaci, Volkan [Bartin University, Faculty of Engineering, Mechanical Engineering Department, 74100 Bartin (Turkey)

    2009-11-15

    An experimental investigation is made to determine the effects of the orifice nozzle number and the inlet pressure on the heating and cooling performance of the counter flow Ranque-Hilsch vortex tube when air and oxygen used as a fluid. The orifices used at these experiments are made of the polyamide plastic material. The thermal conductivity of polyamide plastic material is 0.25 W/m C. Five orifices with nozzle numbers of 2, 3, 4, 5 and 6 have been manufactured and used during the experiments. For each one of the orifices (nozzle numbers) when used with two different fluids, inlet pressures were adjusted from 150 kPa to 700 kPa with 50 kPa increments, and the exergy efficiency was determined. During the experiments, a vortex tube is used with an L/D ratio of 15, and cold mass fraction is held constant at 0.5. As a result of the experimental study, it is determined that the temperature gradient between the hot and cold fluid is decreased with increasing of the orifice nozzle number. (author)

  19. Vortex-assisted low density solvent based demulsified dispersive liquid-liquid microextraction and high-performance liquid chromatography for the determination of organophosphorus pesticides in water samples.

    Science.gov (United States)

    Seebunrueng, Ketsarin; Santaladchaiyakit, Yanawath; Srijaranai, Supalax

    2014-05-01

    A simple, rapid, effective and eco-friendly preconcentration method, vortex-assisted low density solvent based solvent demulsified dispersive liquid-liquid microextraction (VLDS-SD-DLLME), followed by high performance liquid chromatography-diode array detector (HPLC-DAD) analysis, has been developed for the first time for the determination of four organophosphorus pesticides (OPPs) (e.g., azinphos-methyl, parathion-methyl, fenitrothion and diazinon) in environmental water samples. In this preconcentration procedure, an emulsion was obtained after the mixture of extraction solvent (1-dodecanol) and dispersive solvent (acetonitrile, ACN) was injected rapidly into 10 mL of the sample solution. The vortex agitator aided the dispersion of the extraction solvent into the sample solution. After the formation of an emulsion, the demulsifier (ACN) was added, resulting in the rapid separation of the mixture into two phases without centrifugation. Under optimal conditions, the proposed method provided high extraction efficiency (90-99%), good linearity range (0.5-500 ng mL(-1)), low limits of detection (0.25-1 ng mL(-1)) and good repeatability and recoveries were obtained. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. TRANSFORMATION

    Energy Technology Data Exchange (ETDEWEB)

    LACKS,S.A.

    2003-10-09

    Transformation, which alters the genetic makeup of an individual, is a concept that intrigues the human imagination. In Streptococcus pneumoniae such transformation was first demonstrated. Perhaps our fascination with genetics derived from our ancestors observing their own progeny, with its retention and assortment of parental traits, but such interest must have been accelerated after the dawn of agriculture. It was in pea plants that Gregor Mendel in the late 1800s examined inherited traits and found them to be determined by physical elements, or genes, passed from parents to progeny. In our day, the material basis of these genetic determinants was revealed to be DNA by the lowly bacteria, in particular, the pneumococcus. For this species, transformation by free DNA is a sexual process that enables cells to sport new combinations of genes and traits. Genetic transformation of the type found in S. pneumoniae occurs naturally in many species of bacteria (70), but, initially only a few other transformable species were found, namely, Haemophilus influenzae, Neisseria meningitides, Neisseria gonorrheae, and Bacillus subtilis (96). Natural transformation, which requires a set of genes evolved for the purpose, contrasts with artificial transformation, which is accomplished by shocking cells either electrically, as in electroporation, or by ionic and temperature shifts. Although such artificial treatments can introduce very small amounts of DNA into virtually any type of cell, the amounts introduced by natural transformation are a million-fold greater, and S. pneumoniae can take up as much as 10% of its cellular DNA content (40).

  1. Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime

    OpenAIRE

    Karapetrov, G.; Yefremenko, V.; Mihajlović, G; Pearson, J. E.; Iavarone, M.; Novosad, V.; Bader, S. D.

    2012-01-01

    We report on dynamics of non-local Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the non-local voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipula...

  2. Vortex profiles and vortex interactions at the electroweak crossover

    OpenAIRE

    Chernodub, M.N.; Ilgenfritz, E. -M.; Schiller, A.

    1999-01-01

    Local correlations of Z-vortex operators with gauge and Higgs fields (lattice quantum vortex profiles) as well as vortex two-point functions are studied in the crossover region near a Higgs mass of 100 GeV within the 3D SU(2) Higgs model. The vortex profiles resemble certain features of the classical vortex solutions in the continuum. The vortex-vortex interactions are analogous to the interactions of Abrikosov vortices in a type-I superconductor.

  3. Defense Business Transformation: DOD Should Improve Its Planning with and Performance Monitoring of the Military Departments

    Science.gov (United States)

    2016-12-01

    DEFENSE BUSINESS TRANSFORMATION DOD Should Improve Its Planning with and Performance Monitoring of the Military...strategic or business transformation plans , but DOD has not coordinated with the military departments to align their strategic planning efforts for...strategic planning process to develop department- wide business transformation goals and objectives. Further, DOD has not aligned the military departments

  4. TRANSFORMER

    Science.gov (United States)

    Baker, W.R.

    1959-08-25

    Transformers of a type adapted for use with extreme high power vacuum tubes where current requirements may be of the order of 2,000 to 200,000 amperes are described. The transformer casing has the form of a re-entrant section being extended through an opening in one end of the cylinder to form a coaxial terminal arrangement. A toroidal multi-turn primary winding is disposed within the casing in coaxial relationship therein. In a second embodiment, means are provided for forming the casing as a multi-turn secondary. The transformer is characterized by minimized resistance heating, minimized external magnetic flux, and an economical construction.

  5. Novel vortex generator and mode converter for electron beams.

    Science.gov (United States)

    Schattschneider, P; Stöger-Pollach, M; Verbeeck, J

    2012-08-24

    A mode converter for electron vortex beams is described. Numerical simulations, confirmed by experiment, show that the converter transforms a vortex beam with a topological charge m=±1 into beams closely resembling Hermite-Gaussian HG(10) and HG(01) modes. The converter can be used as a mode discriminator or filter for electron vortex beams. Combining the converter with a phase plate turns a plane wave into modes with topological charge m=±1. This combination serves as a generator of electron vortex beams of high brilliance.

  6. PRELATIONSHIP BETWEEN TRANSFORMATIONAL LEADERSHIP, EMPOWERMENT AND FOLLOWERS’ PERFORMANCE: A EMPIRICAL STUDY IN MALAYSIA

    Directory of Open Access Journals (Sweden)

    Azman Ismail

    2009-07-01

    Full Text Available Further research reveals that the effect of transformational leadership on followers’ performance is indirectly affected by empowerment. The nature of this relationship is less emphasized in organizational leadership literature. Therefore, this study was conducted to examine the effect of transformational leadership on followers’ performance and investigate the mediating effect of empowerment in the relationship between transformational leadership and followers’ performance. Findings showed that the relationship between empowerment and transformational leadership had increased followers’ performance. This result confirms that empowerment acts as a full mediating role in the leadership model of the studied organization.

  7. Transformation

    DEFF Research Database (Denmark)

    Peters, Terri

    2011-01-01

    Artiklen diskuterer ordet "transformation" med udgangspunkt i dels hvorledes ordet bruges i arkitektfaglig terminologi og dels med fokus på ordets potentielle indhold og egnethed i samme teminologi....

  8. Performance versus values in sustainability transformation of food systems

    DEFF Research Database (Denmark)

    Alrøe, Hugo F.; Sautier, Marion; Legun, Katharine

    2017-01-01

    -based approaches that aim at communicating and mediating sustainability values to enable coordinated and cooperative action to transform the food system. We identify their respective strengths and weaknesses based on a cross-case analysis of four cases, and propose that the two approaches, likeWeber's two types......Questions have been raised on what role the knowledge provided by sustainability science actually plays in the transition to sustainability and what role it may play in the future. In this paper we investigate different approaches to sustainability transformation of food systems by analyzing...... the rationale behind transformative acts-the ground that the direct agents of change act upon-and how the type of rationale is connected to the role of research and how the agents of change are involved. To do this we employ MaxWeber's distinction between instrumental rationality and value-rationality in social...

  9. Theorizing slum tourism: performing, negotiating and transforming inequality

    NARCIS (Netherlands)

    Dürr, E.; Jaffe, R.

    2012-01-01

    This Exploration focuses on the emerging field of slum tourism research, which has the poten- tial to connect Latin American and Caribbean studies on tourism and urban inequality. Slum tourism involves transforming poverty, squalor and violence into a tourism product. Drawing on both altruism and

  10. Domain formation in the type-II/1 superconductor niobium: Interplay of pinning, geometry, and attractive vortex-vortex interaction

    Science.gov (United States)

    Reimann, Tommy; Schulz, Michael; Mildner, David F. R.; Bleuel, Markus; Brûlet, Annie; Harti, Ralph P.; Benka, Georg; Bauer, Andreas; Böni, Peter; Mühlbauer, Sebastian

    2017-10-01

    Vortex attraction which can cause a bundling of vortices has been observed in a multitude of type-II superconductors. While its underlying mechanisms have been extensively studied, the morphology of the emerging vortex superstructure has only been rarely considered. Here, we present a comprehensive experimental study on the type-II/1 superconductor niobium which focuses on the transformation of its homogeneous vortex lattice into an inhomogeneous domain structure at the onset of vortex attraction. By means of small-angle neutron scattering, ultra-small-angle neutron scattering, and neutron grating interferometry, the vortex lattice and the micrometer-scale vortex domain structure as well as its distribution could be investigated. In particular, we focus on the transformation of the vortex lattice at the transition to the intermediate mixed state, which is characterized by vortex attraction. We have found that the phase separation of the vortex lattice into an irregular domain structure takes place via a process showing strong similarity to spinodal decomposition. While pinning disorders the domain morphology, the characteristic length scale of the domain structure is governed by an interplay of field distortion energy and domain surface tension. Finally, geometric barriers in the disk-shaped samples provoke an inhomogeneous distribution of domains on the macroscopic scale.

  11. A performance-oriented power transformer design methodology using multi-objective evolutionary optimization.

    Science.gov (United States)

    Adly, Amr A; Abd-El-Hafiz, Salwa K

    2015-05-01

    Transformers are regarded as crucial components in power systems. Due to market globalization, power transformer manufacturers are facing an increasingly competitive environment that mandates the adoption of design strategies yielding better performance at lower costs. In this paper, a power transformer design methodology using multi-objective evolutionary optimization is proposed. Using this methodology, which is tailored to be target performance design-oriented, quick rough estimation of transformer design specifics may be inferred. Testing of the suggested approach revealed significant qualitative and quantitative match with measured design and performance values. Details of the proposed methodology as well as sample design results are reported in the paper.

  12. A performance-oriented power transformer design methodology using multi-objective evolutionary optimization

    Directory of Open Access Journals (Sweden)

    Amr A. Adly

    2015-05-01

    Full Text Available Transformers are regarded as crucial components in power systems. Due to market globalization, power transformer manufacturers are facing an increasingly competitive environment that mandates the adoption of design strategies yielding better performance at lower costs. In this paper, a power transformer design methodology using multi-objective evolutionary optimization is proposed. Using this methodology, which is tailored to be target performance design-oriented, quick rough estimation of transformer design specifics may be inferred. Testing of the suggested approach revealed significant qualitative and quantitative match with measured design and performance values. Details of the proposed methodology as well as sample design results are reported in the paper.

  13. A performance-oriented power transformer design methodology using multi-objective evolutionary optimization

    OpenAIRE

    Adly, Amr A.; Abd-El-Hafiz, Salwa K.

    2014-01-01

    Transformers are regarded as crucial components in power systems. Due to market globalization, power transformer manufacturers are facing an increasingly competitive environment that mandates the adoption of design strategies yielding better performance at lower costs. In this paper, a power transformer design methodology using multi-objective evolutionary optimization is proposed. Using this methodology, which is tailored to be target performance design-oriented, quick rough estimation of tr...

  14. Bell’s measure and implementing quantum Fourier transform with orbital angular momentum of classical light

    Science.gov (United States)

    Song, Xinbing; Sun, Yifan; Li, Pengyun; Qin, Hongwei; Zhang, Xiangdong

    2015-01-01

    We perform Bell’s measurement for the non-separable correlation between polarization and orbital angular momentum from the same classical vortex beam. The violation of Bell’s inequality for such a non-separable classical correlation has been demonstrated experimentally. Based on the classical vortex beam and non-quantum entanglement between the polarization and the orbital angular momentum, the Hadamard gates and conditional phase gates have been designed. Furthermore, a quantum Fourier transform has been implemented experimentally. PMID:26369424

  15. Bell's measure and implementing quantum Fourier transform with orbital angular momentum of classical light.

    Science.gov (United States)

    Song, Xinbing; Sun, Yifan; Li, Pengyun; Qin, Hongwei; Zhang, Xiangdong

    2015-09-15

    We perform Bell's measurement for the non-separable correlation between polarization and orbital angular momentum from the same classical vortex beam. The violation of Bell's inequality for such a non-separable classical correlation has been demonstrated experimentally. Based on the classical vortex beam and non-quantum entanglement between the polarization and the orbital angular momentum, the Hadamard gates and conditional phase gates have been designed. Furthermore, a quantum Fourier transform has been implemented experimentally.

  16. Transforming and Turning around Low-Performing Schools: The Role of Online Learning

    Science.gov (United States)

    Corry, Michael; Carlson-Bancroft, Angela

    2014-01-01

    This review of the literature examines online learning as a core strategy for bold, dramatic curricular reform within transformational or turnaround models in improving low-performing K-12 schools. The analysis of the literature in this area found benefits of online learning in transforming and turning around low-performing schools to include: (a)…

  17. Hydrodynamic Vortex on Surfaces

    Science.gov (United States)

    Ragazzo, Clodoaldo Grotta; de Barros Viglioni, Humberto Henrique

    2017-10-01

    The equations of motion for a system of point vortices on an oriented Riemannian surface of finite topological type are presented. The equations are obtained from a Green's function on the surface. The uniqueness of the Green's function is established under hydrodynamic conditions at the surface's boundaries and ends. The hydrodynamic force on a point vortex is computed using a new weak formulation of Euler's equation adapted to the point vortex context. An analogy between the hydrodynamic force on a massive point vortex and the electromagnetic force on a massive electric charge is presented as well as the equations of motion for massive vortices. Any noncompact Riemann surface admits a unique Riemannian metric such that a single vortex in the surface does not move ("Steady Vortex Metric"). Some examples of surfaces with steady vortex metric isometrically embedded in R^3 are presented.

  18. All-electrical magnetic vortex array sensing

    Science.gov (United States)

    Tannous, C.; Gieraltowski, J.

    2016-08-01

    Vortex sensing magnetometers based on arrays of soft magnetic dots are good candidates for high-resolution and accurate spatial magnetic-field estimation. When the arrays are laid out along different spatial directions they can perform tensor gradiometry allowing the measurement of field components and their spatial derivatives as a function of orientation. Detection is based on using spin-polarized currents to counteract vortex displacements or to excite vortex oscillation modes triggered by magnetic-field application. Sensor linearization, field detection range and conditions to obtain large sensitivity electronic compatibility and scalability are discussed.

  19. Vortex Cloud Street during AMTEX 75

    DEFF Research Database (Denmark)

    Jensen, Niels Otto; Agee, E. M.

    1978-01-01

    Strong northerly flow across Cheju Island, Korea, during the 1975 Air Mass Transformation Experiment (AMTEX 75) resulted in a pronounced vortex cloud street to the lee of the island on February 17 1975. This pattern has been studied and explained in terms of classical von Karman eddies shed...

  20. Embracing transformational leadership: team values and the impact of leader behavior on team performance.

    Science.gov (United States)

    Schaubroeck, John; Lam, Simon S K; Cha, Sandra E

    2007-07-01

    The authors investigated the relationship between transformational leadership behavior and group performance in 218 financial services teams that were branches of a bank in Hong Kong and the United States. Transformational leadership influenced team performance through the mediating effect of team potency. The effect of transformational leadership on team potency was moderated by team power distance and team collectivism, such that higher power distance teams and more collectivistic teams exhibited stronger positive effects of transformational leadership on team potency. The model was supported by data in both Hong Kong and the United States, which suggests a convergence in how teams function in the East and West and highlights the importance of team values.

  1. Quenching processes in flame-vortex interactions

    Science.gov (United States)

    Zingale, M.; Niemeyer, J. C.; Timmes, F. X.; Dursi, L. J.; Calder, A. C.; Fryxell, B.; Lamb, D. Q.; MacNeice, P.; Olson, K.; Ricker, P. M.; Rosner, R.; Truran, J. W.; Tufo, H. M.

    2001-10-01

    We show direct numerical simulations of flame-vortex interactions in order to understand quenching of thermonuclear flames. The key question is-can a thermonuclear flame be quenched? If not, the deflagration-detonation transition mechanisms that demand a finely tuned preconditioned region in the interior of a white dwarf are unlikely to work. In these simulations, we pass a steady-state laminar flame through a vortex pair. The vortex pair represents the most severe strain the flame front will encounter inside the white dwarf. We perform a parameter study, varying the speed and size of the vortex pair, in order to understand the quenching process. No quenching is observed in any of the calculations performed to date. .

  2. Holographic Vortex Coronagraph

    Science.gov (United States)

    Palacios, David

    2010-01-01

    A holographic vortex coronagraph (HVC) has been proposed as an improvement over conventional coronagraphs for use in high-contrast astronomical imaging for detecting planets, dust disks, and other broadband light scatterers in the vicinities of stars other than the Sun. Because such light scatterers are so faint relative to their parent stars, in order to be able to detect them, it is necessary to effect ultra-high-contrast (typically by a factor of the order of 1010) suppression of broadband light from the stars. Unfortunately, the performances of conventional coronagraphs are limited by low throughput, dispersion, and difficulty of satisfying challenging manufacturing requirements. The HVC concept offers the potential to overcome these limitations.

  3. Transformational, Transactional Leadership Styles and Job Performance of Academic Leaders

    Science.gov (United States)

    Mahdinezhad, Maryam; Bin Suandi, Turiman; bin Silong, Abu Daud; Omar, Zoharah Binti

    2013-01-01

    In higher learning education, the performance is influenced by many factors. Effective leadership has an imperative role in the better performance and growth of the organization. Yet, several performance efforts were unsuccessful as a result of factors such as satisfactory leadership style of leaders. This study was carried out to identify the…

  4. Influence of Transformational and Transactional Leadership Towards Employee Performance (study at PT Ekistindo, Makassar)

    OpenAIRE

    Idayanti

    2012-01-01

    The purpose of this study was to anallze (1) the significances of the transformational leadership and transactional leadership to employees performance, and (2) the dominant variable affecting employee performance. From the sample that consisted of 102 respondent, the analysis used multiple linear regression to determine a model which best predicts the performance of these firms. Result of this research shown that transformational and transactional leadership variables have significant effect...

  5. Cryptanalysis of Vortex

    DEFF Research Database (Denmark)

    Aumasson, Jean-Philippe; Dunkelman, Orr; Mendel, Florian

    2009-01-01

    Vortex is a hash function that was first presented at ISC'2008, then submitted to the NIST SHA-3 competition after some modifications. This paper describes several attacks on both versions of Vortex, including collisions, second preimages, preimages, and distinguishers. Our attacks exploit flaws...

  6. Abatement of fluorinated compounds using a 2.45 GHz microwave plasma torch with a reverse vortex plasma reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.H.; Cho, C.H.; Shin, D.H. [Plasma Technology Research Center, National Fusion Research Institute, 814-2 Oxikdo-dong, Gunsan-city, Jeollabuk-do (Korea, Republic of); Hong, Y.C., E-mail: ychong@nfri.re.kr [Plasma Technology Research Center, National Fusion Research Institute, 814-2 Oxikdo-dong, Gunsan-city, Jeollabuk-do (Korea, Republic of); Shin, Y.W. [Plasma Technology Research Center, National Fusion Research Institute, 814-2 Oxikdo-dong, Gunsan-city, Jeollabuk-do (Korea, Republic of); School of Advanced Green Energy and Environments, Handong Global University, Heunghae-eup, Buk-gu, Pohang-city, Gyeongbuk (Korea, Republic of)

    2015-08-30

    Highlights: • We developed a microwave plasma torch with reverse vortex reactor (RVR). • We calculated a volume fraction and temperature distribution of discharge gas and waste. • The performance of reverse vortex reactor increased from 29% to 43% than conventional vortex reactor. - Abstract: Abatement of fluorinated compounds (FCs) used in semiconductor and display industries has received an attention due to the increasingly stricter regulation on their emission. We have developed a 2.45 GHz microwave plasma torch with reverse vortex reactor (RVR). In order to design a reverse vortex plasma reactor, we calculated a volume fraction and temperature distribution of discharge gas and waste gas in RVR by ANSYS CFX of computational fluid dynamics (CFD) simulation code. Abatement experiments have been performed with respect to SF{sub 6}, NF{sub 3} by varying plasma power and N{sub 2} flow rates, and FCs concentration. Detailed experiments were conducted on the abatement of NF{sub 3} and SF{sub 6} in terms of destruction and removal efficiency (DRE) using Fourier transform infrared (FTIR). The DRE of 99.9% for NF{sub 3} was achieved without an additive gas at the N{sub 2} flow rate of 150 liter per minute (L/min) by applying a microwave power of 6 kW with RVR. Also, a DRE of SF{sub 6} was 99.99% at the N{sub 2} flow rate of 60 L/min using an applied microwave power of 6 kW. The performance of reverse vortex reactor increased about 43% of NF{sub 3} and 29% of SF{sub 6} abatements results definition by decomposition energy per liter more than conventional vortex reactor.

  7. 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.

    Science.gov (United States)

    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 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.

  8. Athlete Characteristics and Team Competitive Performance as Moderators for the Relationship Between Coach Transformational Leadership and Athlete Performance.

    Science.gov (United States)

    Bormann, Kai C; Schulte-Coerne, Paul; Diebig, Mathias; Rowold, Jens

    2016-06-01

    The goal of this study is to examine the effects of coaches' transformational leadership on player performance. To advance existing research, we examine (a) effects on individual and team performance and (b) consider joint moderating effects of players' win orientation and teams' competitive performance on the leadership- individual performance link. In a three-source sample from German handball teams, we collected data on 336 players and 30 coaches and teams. Results showed positive main effects of transformational leadership's facet of articulating a vision (AV) on team and individual performance and negative main effects of providing an appropriate model (PAM) on team performance. With regard to moderating effects, AV increased and PAM decreased individual performance when both moderators were low, and intellectual stimulation had a positive effect when both were high. This study expands insights into the potential and limitation of transformational leadership with a strong focus on the role of situational contingencies.

  9. Transformational Leadership and the Leadership Performance of Oregon Secondary School Principals

    Science.gov (United States)

    Breaker, Jason Lee

    2009-01-01

    A study of 118 secondary school principals in Oregon was conducted to examine the relationship of transformational leadership to secondary school principals' leadership performance. This study measured the transformational leadership of secondary school principals in Oregon using the "Multifactor Leadership Questionnaire (5X-Short)"…

  10. Analisis Dampak Transformational Leadership terhadap Financial Performance pada Perusahaan Manufaktur di Surabaya

    OpenAIRE

    Siajaya, Stanley Kevin

    2014-01-01

    Penelitian ini bertujuan untuk menguji hubungan antara transformational leadership terhadap financial performance Perusahaan. Peneletian ini dilakukan sebab di Indonesia masih belum banyak peneliti yang mengangkat topik ini serta untuk mengembangkan variabel baru dalam penelitian yang sudah ada Variabel bebas adalah pengaplikasian dari Transformational Leadership. Variabel bebas diukur dengan menggunakan pendektatan definisi operasional dan indikator empirik. Variabel terikat adalah Financial...

  11. Performing Frame Transformations to Correctly Stream Position Data

    Science.gov (United States)

    Franco, Tom

    Unmanned Aerial Vehicles (UAV) are starting to become a more common occurrence today. What started off as highly classified military weapons with little known information, have become part of everyday life for the common individual. UAV's still carry a great deal of importance in paving the way for unmanned flight. UAV's hold major potential for many amazing technological advances within the near future. Drones have become such a common backyard toy for individuals all over the world as well as the way of the future. Major corporations, such as Amazon, are starting to test drones for delivering small packages. Uber has stated that they want to get to the point where cars will be self-driving, already implementing their testing facility for self-driving cars. It is crazy to think that if an order from amazon is processed, it could arrive at the desired destination the same day within minutes of being processed. To get to that point, there is a lot to consider. First, and most importantly, the drone must be largely autonomous with no minimal human control. The drone also must be able to communicate effectively and relay its position to some sort of tracking device, whether it be a GPS signal or software. How would it go about this? What sort of factors make this possible fantasy of the future a tangible reality? The drone must communicate with numerous devices, be in the proper orientation and have the data being streamed be associated with the proper direction. Since there are a variety of potential directions for the drone to move, odds are there will be some sort of data conversion involved. When testing turbomachinery, sensors used to be placed on the rotating piece of machinery and frame transformations were done to relay the data from the rotating frame to that of the inertial frame. Using this concept, exploring the use of frame transformations to relay position data is conducted. Once explore, testing can be conducted to collect data and once the data is

  12. Vortex-assisted liquid-liquid micro-extraction and high-performance liquid chromatography for a higher sensitivity methyl methacrylate determination in biological matrices.

    Science.gov (United States)

    Sousa, Tiago F A; Aniceto, Marta C; Amorim, Célia G; Souto-Lopes, Mariana; Pérez-Mongiovi, Daniel; Montenegro, Maria C B S M; Araújo, Alberto N

    2014-05-01

    A vortex-assisted liquid-liquid micro-extraction coupled with high-performance liquid chromatography, with UV-vis, is proposed to pre-concentrate methyl methacrylate and to improve separation in biological matrices. The use of 1-octanol as extracting phase, its volume, the need for a dispersant agent, the agitation conditions and the cooling time before phase separation were evaluated. In optimum conditions, enrichment factors of 20 (±0.5) and enrichment recovery of 99% were obtained. The straightforward association of this extraction process with the HPLC method, previously regulated by the International Organization for Standardization, afforded a detection limit of 122 ng/mL and a quantification limit of 370 ng/mL. The within-batch precision, relative standard deviation, was 3% for a sample with 1.49 µg/mL and 4% for a sample with 13.4 µg/mL. The results showed a between batch-precision of 21% for experiments performed on five different days, for a sample with a concentration of 1.10 µg/mL in methyl methacrylate. Copyright © 2013 John Wiley & Sons, Ltd.

  13. Experimental characteristics of vortex heaters

    Science.gov (United States)

    Piralishvili, Sh. A.; Novikov, N. N.

    The performance of a Ranque-Hilsch vortex tube is investigated experimentally for the case where the tube operates as a heater, with the mass of the heated gas remaining constant. The results obtained indicate that energy separation zones with sufficiently high (50 percent) relative heating effects can be achieved for a gas flow ratio of unity. A nomogram is presented for calculating the relative and absolute heating effects as a function of the tube geometry.

  14. The Impact of Transformational Leadership on Employee Sustainable Performance: The Mediating Role of Organizational Citizenship Behavior

    Directory of Open Access Journals (Sweden)

    Weiping Jiang

    2017-09-01

    Full Text Available Transformational leadership has drawn extensive attention in management research. In this field, the influence of transformational leadership on employee performance is an important branch. Recent research indicates that organizational citizenship behavior plays a mediating role between transformational leadership and employee performance. However, some of these findings contradict each other. Given the background where greater attention is being paid to transformational leadership in the construction industry, this research aims to find the degree of the influence of transformational leadership on employee sustainable performance, as well as the mediating role of organizational citizenship behavior. A total of 389 questionnaires were collected from contractors and analyzed via structural equation modeling. The findings reveal that employee sustainable performance is positively influenced by transformational leadership. In addition, more than half of that influence is mediated by their organizational citizenship behavior. These findings remind project managers of the need to pay close attention to transformational leadership, to cultivate organizational citizenship behavior, and thereby to eventually improve employee’s sustainable performance.

  15. The Influence of Transformational Leadership on Job Satisfaction, Organizational Commitment,and Employee Performance

    Directory of Open Access Journals (Sweden)

    Marnis Atmojo

    2012-04-01

    Full Text Available This research has four main objectives; first, to prove and analyze the influence of transformational leadership towards employee job satis faction; Second, to prove and analyze the influence of transformational leadership towards organizational commitment; Third, to prove and analyze the influence of transformationalleadership towards employee performance; Fourth, to prove and analyze the influence of organization commitment towards the employee performance. This research involved 146 members of middle management as our research sample namely Head of Department, Plantation Manager, Plant Manager, Head of Bureau/Division, Head Assistant, Head of Strategic Business Unit (SBU, Chief Engineer and Head of Hospital Service. Structural Equation Modeling (SEM was used to test and analyze relationship among the research variables. Research findings are transformational leadership significantly influences job satisfaction, transformational leadership significantly influences the organization commitment. The job satisfaction is shown to have significant influence on employee performance, and organization commitment significantly influences the employee performance.

  16. Computational investigation of the temperature separation in vortex chamber

    Energy Technology Data Exchange (ETDEWEB)

    Anish, S. [National Institute of Technology Karnataka, Mangalore (India); Setoguchi, T. [Institute of Ocean Energy, Saga University (Japan); Kim, H. D. [Andong National University, Andong (Korea, Republic of)

    2014-06-15

    The vortex chamber is a mechanical device, without any moving parts that separates compressed gas into a high temperature region and a low temperature region. Functionally vortex chamber is similar to a Ranque-Hilsch vortex tube (RVHT), but it is a simpler and compact structure. The objective of the present study is to investigate computationally the physical reasoning behind the energy separation mechanism inside a vortex chamber. A computational analysis has been performed using three-dimensional compressible Navier Stokes equations. A fully implicit finite volume scheme was used to solve the governing equations. A commercial software ANSYS CFX is used for this purpose. The computational predictions were validated with existing experimental data. The results obtained show that the vortex chamber contains a large free vortex zone and a comparatively smaller forced vortex region. The physical mechanism that causes the heating towards periphery of the vortex chamber is identified as the work done by the viscous force. The cooling at the center may be due to expansion of the flow. The extent of temperature separation greatly depends on the outer diameter of the vortex chamber. A small amount of compression is observed towards the periphery of the vortex chamber when the outer diameter is reduced.

  17. Experimental investigation and exergy analysis of the performance of a counter flow Ranque-Hilsch vortex tube with regard to nozzle cross-section areas

    Energy Technology Data Exchange (ETDEWEB)

    Dincer, K.; Avci, A.; Berber, A. [Dept. of Mechanical Eng., Fac. of Eng. and Architecture, Selcuk Univ., Selcuklu, Konya (Turkey); Baskaya, S. [Dept. of Mechanical Eng., Fac. of Eng. and Architecture, Gazi Univ., Maltepe, Ankara (Turkey)

    2010-08-15

    Exergy analysis and performance of a Ranque-Hilsch Vortex Tube (RHVT) with various nozzle cross-section areas (NCSA = 3 x 3, 4 x 4, 5 x 5 mm{sup 2}) were determined under inlet pressures (P{sub i}) of 260, 300 kPa (absolute) pressurized air. The maximum difference in the temperatures of hot output and cold output streams was obtained for NCSA = 3 x 3 mm{sup 2}. The total inlet exergy (sum E{sub i}), total outlet exergy (sum E{sub O}), total lost exergy (sum E{sub Lost}) and exergy efficiency ({eta}, %) were calculated. It was determined that the exergy efficiency of the system, varied between 1% and 39%, and the highest exergy efficiency was obtained for NCSA = 3 x 3 mm{sup 2}. The exergy efficiency strongly depends on the level of P{sub i}, {xi} and v{sub cold}. Variation of the exergy efficiency decreased with decreasing P{sub i}, {xi}, v{sub cold} and the highest and lowest exergy efficiencies were found when the values of P{sub i}, {xi}, v{sub cold} reached maximum and minimum levels, respectively. (author)

  18. Vortex dominated flows

    CERN Document Server

    Ting, Lu; Knio, Omar M

    2007-01-01

    Addressed to both graduate students and researchers this monograph provides in-depth analyses of vortex dominated flows via matched and multiscale asymptotics, and it demonstrates how insight gained through these analyses can be exploited in the construction of robust, efficient, and accurate numerical techniques. The dynamics of slender vortex filaments is discussed in detail, including fundamental derivations, compressible core structure, weakly non-linear limit regimes, and associated numerical methods. Similarly, the volume covers asymptotic analysis and computational techniques for weakly compressible flows involving vortex generated sound and thermoacoustics.

  19. Performance through transformation of identity in road cycling

    DEFF Research Database (Denmark)

    Stilling Olesen, Jesper

    In this paper I investigate the relationship between skills and identity of an elite cyclist, who during his career managed to become a big star in the professional peleton. This is Jesper Skibby. The paper is based on a reading of his autobiography "Forstå mig ret." In the book he reproduces his...... career chronologically progressing through a series of identities from an amateur rider, to a team rider and a captain. On the surface and in his own self-understanding these identities and the corresponding competencies belong to the individual. But on closer reading based on actor-network theory......, it turns out that the conception of the self-reliant, performing individual does not hold. In this paper I will argue that the rider achieve his skills through the deletion of personal boundaries and re-assembly with an ever-wider range of actors in the surrounding world. To develop as a rider...

  20. Transforming RNA-Seq data to improve the performance of prognostic gene signatures.

    Science.gov (United States)

    Zwiener, Isabella; Frisch, Barbara; Binder, Harald

    2014-01-01

    Gene expression measurements have successfully been used for building prognostic signatures, i.e for identifying a short list of important genes that can predict patient outcome. Mostly microarray measurements have been considered, and there is little advice available for building multivariable risk prediction models from RNA-Seq data. We specifically consider penalized regression techniques, such as the lasso and componentwise boosting, which can simultaneously consider all measurements and provide both, multivariable regression models for prediction and automated variable selection. However, they might be affected by the typical skewness, mean-variance-dependency or extreme values of RNA-Seq covariates and therefore could benefit from transformations of the latter. In an analytical part, we highlight preferential selection of covariates with large variances, which is problematic due to the mean-variance dependency of RNA-Seq data. In a simulation study, we compare different transformations of RNA-Seq data for potentially improving detection of important genes. Specifically, we consider standardization, the log transformation, a variance-stabilizing transformation, the Box-Cox transformation, and rank-based transformations. In addition, the prediction performance for real data from patients with kidney cancer and acute myeloid leukemia is considered. We show that signature size, identification performance, and prediction performance critically depend on the choice of a suitable transformation. Rank-based transformations perform well in all scenarios and can even outperform complex variance-stabilizing approaches. Generally, the results illustrate that the distribution and potential transformations of RNA-Seq data need to be considered as a critical step when building risk prediction models by penalized regression techniques.

  1. Three-wave electron vortex lattices for measuring nanofields.

    Science.gov (United States)

    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.

  2. High performance simulations for transformational earthquake risk assessments

    Science.gov (United States)

    McCallen, D. B.; Larsen, S. C.

    2009-07-01

    Earthquakes occurring around the world are responsible for extensive loss of life and infrastructure damage. On average, 1100 earthquakes with significant damage potential occur world-wide per year, and a major societal challenge is to design a human environment that contains appropriate earthquake resistance. Design of critical infrastructure such as large buildings, bridges, industrial facilities and nuclear power plants in seismically active regions is a significant scientific and engineering challenge that encompasses the multiple disciplines of geophysics, geotechnical and structural engineering. Because of the great complexities in earthquake physical processes, traditional approaches to seismic hazard assessment have relied heavily on historical earthquake observations. In this approach, observational data from many locations is homogenized into an empirical assessment of earthquake hazard at any specific site of interest. With major advancements in high performance computing platforms and algorithms, it is now possible to utilize physics-based predictive models to gain enhanced insight about site-specific earthquake ground motions and infrastructure response. This paper discusses recent advancements in geophysics and infrastructure simulations and future challenges in implementing advanced simulations for both earthquake hazard (future ground motions) and earthquake risk (infrastructure response and damage) assessments.

  3. Vortex and source rings

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The velocity field, vector potential and velocity gradient of a vortex ring is derived in this chapter. The Biot-Savart law for the vector potential and velocity is expressed in a first section. Then, the flow is derived at specific locations: on the axis, near the axis and in the far field where...... the analogy to a doublet field is made. The following section derive the value of the vector potential and velocity field in the full domain. The expression for the velocity gradient is also provided since it may be relevant in a simulation with vortex particles and vortex rings. Most of this chapter...... is dedicated to vortex rings. Source rings are only briefly mentioned....

  4. The singing vortex.

    Science.gov (United States)

    Arndt, R; Pennings, P; Bosschers, J; van Terwisga, T

    2015-10-06

    Marine propellers display several forms of cavitation. Of these, propeller-tip vortex cavitation is one of the important factors in propeller design. The dynamic behaviour of the tip vortex is responsible for hull vibration and noise. Thus, cavitation in the vortices trailing from tips of propeller blades has been studied extensively. Under certain circumstances cavitating vortices have been observed to have wave-like disturbances on the surfaces of vapour cores. Intense sound at discrete frequencies can result from a coupling between tip vortex disturbances and oscillating sheet cavitation on the surfaces of the propeller blades. This research article focuses on the dynamics of vortex cavitation and more in particular on the energy and frequency content of the radiated pressures.

  5. Effects of angular gain transformations between movement and visual feedback on coordination performance in unimanual circling

    Directory of Open Access Journals (Sweden)

    Martina eRieger

    2014-03-01

    Full Text Available Tool actions are characterized by a transformation (of spatio-temporal and/or force-related characteristics between movements and their resulting consequences in the environment. This transformation has to be taken into account, when planning and executing movement and its existence may affect performance. In the present study we investigated how angular gain transformations between movement and visual feedback during circling movements affect coordination performance. Participants coordinated the visual feedback (feedback dot with a continuously circling stimulus (stimulus dot on a computer screen in order to produce mirror symmetric trajectories of them. The movement angle was multiplied by a gain factor (0.5 to 2; 9 levels before it was presented on the screen. Thus, the angular gain transformations changed the spatio-temporal relationship between the movement and its feedback in visual space, and resulted in a non-constant mapping of movement to feedback positions. Coordination performance was best with gain = 1. With high gains the feedback dot was in lead of the stimulus dot, with small gains it lagged behind. Anchoring (reduced movement variability occurred when the two trajectories were close to each other. Awareness of the transformation depended on the deviation of the gain from 1. In conclusion, the size of an angular gain transformation as well as its mere presence influence performance in a situation in which the mapping of movement positions to visual feedback positions is not constant. When designing machines or tools that involve transformations between movements and their external consequences, one should be aware that the mere presence of angular gains may result in performance decrements and that there can be flaws in the representation of the transformation.

  6. Direct Numerical Simulation of Twin Swirling Flow Jets: Effect of Vortex-Vortex Interaction on Turbulence Modification

    Directory of Open Access Journals (Sweden)

    Wenkai Xu

    2014-01-01

    Full Text Available A direct numerical simulation (DNS was carried out to study twin swirling jets which are issued from two parallel nozzles at a Reynolds number of Re = 5000 and three swirl levels of S = 0.68, 1.08, and 1.42, respectively. The basic structures of vortex-vortex interaction and temporal evolution are illustrated. The characteristics of axial variation of turbulent fluctuation velocities, in both the near and far field, in comparison to a single swirling jet, are shown to explore the effects of vortex-vortex interaction on turbulence modifications. Moreover, the second order turbulent fluctuations are also shown, by which the modification of turbulence associated with the coherent or correlated turbulent fluctuation and turbulent kinetic energy transport characteristics are clearly indicated. It is found that the twin swirling flow has a fairly strong localized vortex-vortex interaction between a pair of inversely rotated vortices. The location and strength of interaction depend on swirl level greatly. The modification of vortex takes place by transforming large-scale vortices into complex small ones, whereas the modulation of turbulent kinetic energy is continuously augmented by strong vortex modification.

  7. Role of Reversible Phase Transformation for Strong Piezoelectric Performance at the Morphotropic Phase Boundary

    Science.gov (United States)

    Liu, Hui; Chen, Jun; Huang, Houbing; Fan, Longlong; Ren, Yang; Pan, Zhao; Deng, Jinxia; Chen, Long-Qing; Xing, Xianran

    2018-01-01

    A functional material with coexisting energetically equivalent phases often exhibits extraordinary properties such as piezoelectricity, ferromagnetism, and ferroelasticity, which is simultaneously accompanied by field-driven reversible phase transformation. The study on the interplay between such phase transformation and the performance is of great importance. Here, we have experimentally revealed the important role of field-driven reversible phase transformation in achieving enhanced electromechanical properties using in situ high-energy synchrotron x-ray diffraction combined with 2D geometry scattering technology, which can establish a comprehensive picture of piezoelectric-related microstructural evolution. High-throughput experiments on various Pb /Bi -based perovskite piezoelectric systems suggest that reversible phase transformation can be triggered by an electric field at the morphotropic phase boundary and the piezoelectric performance is highly related to the tendency of electric-field-driven phase transformation. A strong tendency of phase transformation driven by an electric field generates peak piezoelectric response. Further, phase-field modeling reveals that the polarization alignment and the piezoelectric response can be much enhanced by the electric-field-driven phase transformation. The proposed mechanism will be helpful to design and optimize the new piezoelectrics, ferromagnetics, or other related functional materials.

  8. Unified transform architecture for AVC, AVS, VC-1 and HEVC high-performance codecs

    Science.gov (United States)

    Dias, Tiago; Roma, Nuno; Sousa, Leonel

    2014-12-01

    A unified architecture for fast and efficient computation of the set of two-dimensional (2-D) transforms adopted by the most recent state-of-the-art digital video standards is presented in this paper. Contrasting to other designs with similar functionality, the presented architecture is supported on a scalable, modular and completely configurable processing structure. This flexible structure not only allows to easily reconfigure the architecture to support different transform kernels, but it also permits its resizing to efficiently support transforms of different orders (e.g. order-4, order-8, order-16 and order-32). Consequently, not only is it highly suitable to realize high-performance multi-standard transform cores, but it also offers highly efficient implementations of specialized processing structures addressing only a reduced subset of transforms that are used by a specific video standard. The experimental results that were obtained by prototyping several configurations of this processing structure in a Xilinx Virtex-7 FPGA show the superior performance and hardware efficiency levels provided by the proposed unified architecture for the implementation of transform cores for the Advanced Video Coding (AVC), Audio Video coding Standard (AVS), VC-1 and High Efficiency Video Coding (HEVC) standards. In addition, such results also demonstrate the ability of this processing structure to realize multi-standard transform cores supporting all the standards mentioned above and that are capable of processing the 8k Ultra High Definition Television (UHDTV) video format (7,680 × 4,320 at 30 fps) in real time.

  9. Transformational leadership and safety performance among nurses: the mediating role of knowledge-related job characteristics.

    Science.gov (United States)

    Lievens, Ilse; Vlerick, Peter

    2014-03-01

    To report the impact of transformational leadership on two dimensions of nurses' safety performance (i.e. safety compliance and safety participation) and to study the mediating role of knowledge-related job characteristics in this relationship. Safety performance refers to the behaviours that employees exhibit to adhere to safety guidelines and to promote health and safety at their workplace. Nurses' safety performance is a major challenge for healthcare settings, urging the need to identify the key determinants and psychological mechanisms that influence it. A cross-sectional survey study. The study was carried out in September 2010 in a large Belgian hospital. We used self-administered questionnaires; 152 nurses participated. The hypotheses were tested using hierarchical regression analyses. In line with our first hypothesis, the results show that transformational leadership exerted a significant positive impact on both dimensions of nurses' safety performance. This positive relation was mediated by knowledge-related job characteristics, supporting our second hypothesis. Head nurses' transformational leadership can enhance nurses' compliance with and participation in safety. Furthermore, transformational head nurses are able to influence the perception that their nurses have about the kind and amount of knowledge in their job, which can also lead to increases in both dimensions of nurses' safety performance. This study therefore demonstrates the key impact that transformational head nurses have, both directly and indirectly, on the safety performance of their nurses. © 2013 John Wiley & Sons Ltd.

  10. The Influence of Transformational Leadership on Job Satisfaction, Organizational Commitment,and Employee Performance

    Directory of Open Access Journals (Sweden)

    Marnis Atmojo

    2012-08-01

    Full Text Available This research has four main objectives; first, to prove and analyze the influence of transformational leadership towards employee job satis faction; Second, to prove and analyze the influence of transformationalleadership towards organizational commitment; Third, to prove and analyze the influence of transformational leadership towards employee performance; Fourth, to prove and analyze the influence of organization commitment towards the employee performance. This research involved 146 members of middle management as our research sample namely Head of Department, Plantation Manager, Plant Manager, Head of Bureau/Division, Head Assistant, Head of Strategic Business Unit (SBU, Chief Engineer and Head of Hospital Service. Structural Equation Modeling (SEM was used to test and analyze relationship among the research variables. Research findings are transformationalleadership significantly influences job satisfaction, transformational leadership significantly influences the organization commitment. The job satisfaction is shown to have significant influence on employee performance, and organization commitment significantly influences the employee performance.

  11. Redesigned High Schools for Transformed STEM Learning: Performance Assessment Pilot Outcome

    Science.gov (United States)

    Ernst, Jeremy Vaughn; Glennie, Elizabeth J.

    2015-01-01

    This performance assessment pilot study was a major research component of the overall National Science Foundation funded Redesigned High Schools for Transformed STEM Learning Project. Secondary Earth/Environmental Science students' abilities to translate cognitive knowledge into demonstrable performance-based proficiencies were specifically…

  12. Vortex lattice transitions in YNi 2 B 2 C

    Indian Academy of Sciences (India)

    We have performed extensive small-angle neutron scattering (SANS) diffraction studies of the vortex lattice in single crystal YNi2B2C for B | | c . High-resolution SANS, combined with a field-oscillation vortex lattice preparation technique, allows us to separate Bragg scattered intensities from two orthogonal domains and ...

  13. A nonabelian particle–vortex duality

    Directory of Open Access Journals (Sweden)

    Jeff Murugan

    2016-02-01

    Full Text Available We define a nonabelian particle–vortex duality as a 3-dimensional analogue of the usual 2-dimensional worldsheet nonabelian T-duality. The transformation is defined in the presence of a global SU(2 symmetry and, although derived from a string theoretic setting, we formulate it generally. We then apply it to so-called “semilocal strings” in an SU(2G×U(1L gauge theory, originally discovered in the context of cosmic string physics.

  14. Transformational Leaders and Work Performance: The Mediating Roles of Identification and Self-efficacy

    Directory of Open Access Journals (Sweden)

    Flávia Cavazotte

    2013-10-01

    Full Text Available In this study we investigate the connections between transformational leadership and subordinate formal and contextual performance among Brazilian employees. We also proposed and tested two mediating processesthrough which transformational leaders would enhance the performance of their staff: stronger follower identification with the leader and efficacy beliefs. These relations were tested with a sample of 107 managers from a multinational company that operates in the financial sector. The proposed structural equation model was assessed with Partial Least Squares (PLS techniques. The results suggest that perceived transformational leadership is associated with higher levels of task performance and helping behaviors. Moreover, the proposed mediating processes were empirically supported. We discuss implications for theory and practice.

  15. Integrating dependency on the leader and empowerment into the transformational leadership-creative performance relationship

    Directory of Open Access Journals (Sweden)

    Tobias Kollmann

    2013-03-01

    Full Text Available Previous literature highlights employees’ creativity as an important means of fostering innovation and competitiveadvantage in companies. Transformational leadership is an approach aimed at stimulating and encouraging thecreative performance of employees. However, contradictory empirical fi ndings indicate that the relationship betweentransformational leadership and creativity may be more complex than a simple direct link. Drawing from the existingliterature, we propose that dependency on the leader is a partial mediator of this relationship, impeding employees’ creativity.Synthesizing theories of leadership and creativity, we propose that empowerment, as a moderator, is able to reducethe dependency on the leader caused by transformational leadership as well as contribute to turning possible negativeoutcomes of transformational leadership on creative performance into positive outcomes. The fi ndings of a PLS analysisof 271 employees support the predicted mediating and moderating effects. Our results indicate that the transformationalleadership style should be combined with empowering behavior to enhance employees’ creative performance.

  16. Studies on the coupling transformer to improve the performance of microwave ion source.

    Science.gov (United States)

    Misra, Anuraag; Pandit, V S

    2014-06-01

    A 2.45 GHz microwave ion source has been developed and installed at the Variable Energy Cyclotron Centre to produce high intensity proton beam. It is operational and has already produced more than 12 mA of proton beam with just 350 W of microwave power. In order to optimize the coupling of microwave power to the plasma, a maximally flat matching transformer has been used. In this paper, we first describe an analytical method to design the matching transformer and then present the results of rigorous simulation performed using ANSYS HFSS code to understand the effect of different parameters on the transformed impedance and reflection and transmission coefficients. Based on the simulation results, we have chosen two different coupling transformers which are double ridged waveguides with ridge widths of 24 mm and 48 mm. We have fabricated these transformers and performed experiments to study the influence of these transformers on the coupling of microwave to plasma and extracted beam current from the ion source.

  17. 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.

    Science.gov (United States)

    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.

  18. THE INFLUENCE OF ORGANIZATIONAL CLIMATE, TRANSFORMATIONAL LEADERSHIP, AND WORK MOTIVATION ON TEACHER JOB PERFORMANCE

    Directory of Open Access Journals (Sweden)

    K. Kartini

    2017-07-01

    Full Text Available This research aimed at investigating the influence of organizational climate, transformational leadership, and work motivation on teacher job performance at Pondok Modern Tazakka, Batang - Central Java.The research using a quantitative approach with survey method. Amount of the samples in this research are 55 teachers that selected randomly. The data were analyzed by using descriptive statistics and inferential statistic using path analysis. (1 organizational climate have positive direct effect on teacher performance with path coefficient (py1 = 0,257 and t-count 2,963> t-table 1,684; (2 transformational leadership have positive direct effect on teacher performance with path coefficient (py2 = 0,489 and t-count 5,164> t-table 1,684, (3 work motivation have positive direct effect to teacher performance with path coefficient (py3 = 0,261 and t count 2,42> t-table 1,684, (4 organizational climate have positive direct effect (p31 = 0.391 and t-count 3.990> t-table 1.684, and (5 transformational leadership have a direct positive effect on work motivation with path coefficient (p32 = 0.526 and t-count 5,376> t- table 1,684. The Conclusion is organizational climate, transformational leadership, and work motivation have a direct effect on teacher job performance. Organizational climate and transformational leadership also have a direct effect on teacher work motivation. Therefore to improve teacher job performance, organizational climate, transformational leadership, and work motivation must be considered to be improved.

  19. Symmetrical collision of multiple vortex rings

    Science.gov (United States)

    Hernández, R. H.; Reyes, T.

    2017-10-01

    In this work, we investigate the motion, interaction, and simultaneous collision between many initially stable vortex rings arranged symmetrically in two initial configurations, three and six rings making an angle of 60 and 120° between their straight path lines, respectively. We report results for laminar vortex rings in air obtained through numerical simulations of the ring velocity, pressure, and vorticity fields, both in free flight and during the entire collision. Each collision was studied for small Reynolds numbers R e formed by laterally expanding dipolar arms with top and bottom secondary vortex rings. The case of six colliding rings produces, as secondary structures, two big rings moving in opposite directions, a process that reminds us of the head-on collision of two rings [T. T. Lim and T. B. Nickels, "Instability and reconnection in the head-on collision of two vortex rings," Nature 357, 225-227 (1992)] under a hypothetical time reversal transformation. Both collisions display a characteristic kinetic energy evolution where mean collision stages can be identified within the range of Reynolds numbers investigated here.

  20. Vortex Characterization for Engineering Applications

    Energy Technology Data Exchange (ETDEWEB)

    Jankun-Kelly, M; Thompson, D S; Jiang, M; Shannahan, B; Machiraju, R

    2008-01-30

    Realistic engineering simulation data often have features that are not optimally resolved due to practical limitations on mesh resolution. To be useful to application engineers, vortex characterization techniques must be sufficiently robust to handle realistic data with complex vortex topologies. In this paper, we present enhancements to the vortex topology identification component of an existing vortex characterization algorithm. The modified techniques are demonstrated by application to three realistic data sets that illustrate the strengths and weaknesses of our approach.

  1. Vorticity and vortex dynamics

    CERN Document Server

    Wu, Jie-Zhi; Zhou, M-D

    2006-01-01

    The importance of vorticity and vortex dynamics has now been well rec- nized at both fundamental and applied levels of ?uid dynamics, as already anticipatedbyTruesdellhalfcenturyagowhenhewrotethe?rstmonograph onthesubject, The Kinematics of Vorticity(1954);andasalsoevidencedby the appearance of several books on this ?eld in 1990s. The present book is characterizedbythefollowingfeatures: 1. A basic physical guide throughout the book. The material is directed by a basic observation on the splitting and coupling of two fundamental processes in ?uid motion, i.e., shearing (unique to ?uid) and compre- ing/expanding.Thevorticityplaysakeyroleintheformer,andavortex isnothingbuta?uidbodywithhighconcentrationofvorticitycompared to its surrounding ?uid. Thus, the vorticity and vortex dynamics is - cordinglyde?nedasthetheoryofshearingprocessanditscouplingwith compressing/expandingprocess. 2. A description of the vortex evolution following its entire life.Thisbegins from the generation of vorticity to the formation of thi...

  2. Quantum vortex reconnections

    Science.gov (United States)

    Zuccher, S.; Caliari, M.; Baggaley, A. W.; Barenghi, C. F.

    2012-12-01

    We study reconnections of quantum vortices by numerically solving the governing Gross-Pitaevskii equation. We find that the minimum distance between vortices scales differently with time before and after the vortex reconnection. We also compute vortex reconnections using the Biot-Savart law for vortex filaments of infinitesimal thickness, and find that, in this model, reconnections are time symmetric. We argue that the likely cause of the difference between the Gross-Pitaevskii model and the Biot-Savart model is the intense rarefaction wave which is radiated away from a Gross-Pitaeveskii reconnection. Finally we compare our results to experimental observations in superfluid helium and discuss the different length scales probed by the two models and by experiments.

  3. Comparative performance evaluation of transform coding in image pre-processing

    Science.gov (United States)

    Menon, Vignesh V.; NB, Harikrishnan; Narayanan, Gayathri; CK, Niveditha

    2017-07-01

    We are in the midst of a communication transmute which drives the development as largely as dissemination of pioneering communication systems with ever-increasing fidelity and resolution. Distinguishable researches have been appreciative in image processing techniques crazed by a growing thirst for faster and easier encoding, storage and transmission of visual information. In this paper, the researchers intend to throw light on many techniques which could be worn at the transmitter-end in order to ease the transmission and reconstruction of the images. The researchers investigate the performance of different image transform coding schemes used in pre-processing, their comparison, and effectiveness, the necessary and sufficient conditions, properties and complexity in implementation. Whimsical by prior advancements in image processing techniques, the researchers compare various contemporary image pre-processing frameworks- Compressed Sensing, Singular Value Decomposition, Integer Wavelet Transform on performance. The paper exposes the potential of Integer Wavelet transform to be an efficient pre-processing scheme.

  4. Numerical investigation of vortex shedding and vortex-induced vibration for flexible riser models

    Directory of Open Access Journals (Sweden)

    Zheng-Shou Chen

    2010-06-01

    Full Text Available The numerical study about the vortex-induced vibration and vortex shedding in the wake has been presented. Prior to the numerical simulation of flexible riser systems concerning engineering conditions, efficiency validating of the proposed FSI solution method have been performed. The comparison between numerical simulation and published experimental data shows that the CFD method designed for FSI solution could give acceptable result for the VIV prediction of flexible riser/pipe system. As meaningful study on VIV and vortex shedding mode with the focus on flexible riser model systems, two kinds of typical simulation cases have been carried out. One was related to the simulation of vortex visualization in the wake for a riser model subject to forced oscillation, and another was related to the simulation of fluid-structure interaction between the pipes of coupled multi-assembled riser system. The result from forced oscillation simulation shows that the vortex-induced vibration with high response frequency but small instantaneous vibration amplitude contributes to vortex conformation as much as the forced oscillation with large normalized amplitude does, when the frequency of forced oscillation was relatively high. In the multi-assembled riser systems, it has been found that the external current velocity and the distance between two pipes are the critical factors to determine the vibration state and the steady vibration state emerging in quad-pipe system may be destroyed more easily than dual-pipe system.

  5. Transformational leadership and employee safety performance: a within-person, between-jobs design.

    Science.gov (United States)

    Inness, Michelle; Turner, Nick; Barling, Julian; Stride, Chris B

    2010-07-01

    We investigated the extent to which the safety performance (i.e., self-reported safety compliance and safety participation) of employees with 2 jobs was predicted by their respective supervisors' transformational leadership behaviors. We compared 2 within-person models: a context-specific model (i.e., transformational leadership experienced by employees in 1 context related to those same employees' safety performance only in that context) and a context-spillover model (i.e., transformational leadership experienced by employees in 1 context related to those same employees' safety performance in the same and other contexts). Our sample comprised 159 "moonlighters" (73 men, 86 women): employees who simultaneously hold 2 different jobs, each with a different supervisor, providing within-person data on the influence of different supervisors on employee safety performance across 2 job contexts. Having controlled for individual differences (negative affectivity and conscientiousness) and work characteristics (e.g., hours worked and length of relationship with supervisor), the context-specific model provided the best fit to the data among alternative nested models. Implications for the role of transformational leadership in promoting workplace safety are discussed.

  6. Transformational leadership climate : Performance linkages, mechanisms, and boundary conditions at the organizational level

    NARCIS (Netherlands)

    Menges, J.; Walter, F.; Vogel, B.; Bruch, H.

    2011-01-01

    Transformational leadership (TFL) climate describes the degree to which leaders throughout an organization engage in TFL behaviors. In this study, we investigate performance linkages, mechanisms, and boundary conditions of TFL climate at the organizational level of analysis. In a sample of 158

  7. Transforming Input Into Output : How Downward Networking Mediates the Effect of External Networking on Organizational Performance

    NARCIS (Netherlands)

    van den Bekerom, Petra; Schalk, Jelmer; Torenvlied, René

    2017-01-01

    One of the core assumptions of the open systems perspective is that management facilitates the technical flows that transform resources and demands into output, which ultimately affects the organization’s performance. This article sheds light on the managerial throughput hypothesis by testing the

  8. Performing Cultural Work in Demographically Changing Schools: Implications for Expanding Transformative Leadership Frameworks

    Science.gov (United States)

    Cooper, Camille Wilson

    2009-01-01

    Purpose: Marginalizing dynamics can emerge in school communities that are experiencing rapid demographic change, even when led by equity-oriented principals. The purpose of this article is to consider how educators can serve as transformative leaders through their performing cultural work that addresses inequity, crosses sociocultural boundaries,…

  9. Extension of Friedel's law to Vortex Beam Diffraction

    CERN Document Server

    Juchtmans, Roeland; Verbeeck, Jo

    2016-01-01

    Friedel's law states that the modulus of the Fourier transform of real functions is centrosymmetric, while the phase is antisymmetric. As a consequence of this, elastic scattering of plane wave photons or electrons within the first-order Born-approximation as well as Fraunhofer diffraction on any aperture, is bound to result in centrosymmetric diffraction patterns. Friedel's law, however, does not apply for vortex beams, and centrosymmetry in general is not present in their diffraction patterns. In this work we extend Friedel's law for vortex beams by showing that the diffraction patterns of vortex beams with opposite topological charge, scattered on the same two dimensional potential, always are centrosymmetric to one another, regardless of the symmetry of the scattering object. We verify our statement by means of numerical simulations and experimental data. Our research provides deeper understanding in vortex beam diffraction and can be used to design new experiments to measure the topological charge of vor...

  10. Transformational Leadership Influence on Follower Performance through Upward Knowledge Management and Organizational Learning

    Directory of Open Access Journals (Sweden)

    Ali Osman Uymaz

    2015-06-01

    Full Text Available This article analyzes the direct and indirect effects of transformational leadership on follower performance through upward knowledge management and organizational learning. The research has been carried out in a company that has formed learning organization teams for organizational growth. 247 employees have participated in this study. After applying a confirmatory factor analysis to the scales used in the research, the relationship among research variables has been analyzed by using the structural equation model (SEM. The results of the research has determined that: a transformational leadership has a positive effect on follower performance through upward knowledge management and organizational learning; b upward knowledge management does not only directly and positively impact follower performance but also has a positive but indirect effect through organizational learning; c organizational learning has a direct and positive effect on follower performance.

  11. Green Transformational Leadership and Green Performance: The Mediation Effects of Green Mindfulness and Green Self-Efficacy

    Directory of Open Access Journals (Sweden)

    Yu-Shan Chen

    2014-09-01

    Full Text Available No prior literature explores the influence of green transformational leadership on green performance, thus, this study develops a novel research framework to fill the research gap. This study investigates the influence of green transformational leadership on green performance and discusses the mediation effects of green mindfulness and green self-efficacy by means of structural equation modeling (SEM. The results indicate that green transformational leadership positively influences green mindfulness, green self-efficacy, and green performance. Moreover, this study demonstrates that the positive relationship between green transformational leadership and green performance is partially mediated by the two mediators: green mindfulness and green self-efficacy. It means that green transformational leadership can not only directly affect green performance positively but also indirectly affect it positively through green mindfulness and green self-efficacy. Therefore, firms need to raise their green transformational leadership, green mindfulness, and green self-efficacy to increase their green performance.

  12. Propagation of sharply autofocused ring Airy Gaussian vortex beams.

    Science.gov (United States)

    Chen, Bo; Chen, Chidao; Peng, Xi; Peng, Yulian; Zhou, Meiling; Deng, Dongmei

    2015-07-27

    Controlling the focal length and the intensity of the optical focus in the media is an important task. Here we investigate the propagation properties of the sharply autofocused ring Airy Gaussian vortex beams numerically and some numerical experiments are performed. We introduce the distribution factor b into the initial beams, and discuss the influences for the beams. With controlling the factor b, the beams that tend to a ring Airy vortex beam with the smaller value, or a hollow Gaussian vortex beam with the larger one. By a choice of initial launch condition, we find that the number of topological charge of the incident beams, as well as its size, greatly affect the focal intensity and the focal length of the autofocused ring Airy Gaussian vortex beams. Furthermore, we show that the off-axis autofocused ring Airy Gaussian beams with vortex pairs can be implemented.

  13. Effects of trailing jet instability on vortex ring formation

    Science.gov (United States)

    Zhao, Wei; Frankel, Steven H.; Mongeau, Luc G.

    2000-03-01

    Numerical simulations of an impulsively started jet were performed in order to investigate the effects of trailing jet instability on axisymmetric vortex ring formation. The predictions were compared to experimental results reported in the literature and to recently published numerical results. The total and vortex ring circulations were found to be in good agreement with both the experimental and the numerical results. The presence of a universal formation time scale was confirmed. The results also highlighted an important interaction between an instability which develops in the trailing jet for large discharge times and the dynamics of the head vortex ring. This interaction accelerates the process by which the vortex ring detaches from the trailing jet and has a significant effect on the vortex ring circulation.

  14. Vortex wakes of a flapping foil

    DEFF Research Database (Denmark)

    Schnipper, Teis; Andersen, Anders Peter; Bohr, Tomas

    2009-01-01

    We present an experimental study of a symmetric foil performing pitching oscillations in a vertically flowing soap film. By varying the frequency and amplitude of the oscillation we visualize a variety of wakes with up to 46 vortices per oscillation period, including von Karman vortex street...

  15. Soliton algebra by vortex-beam splitting.

    Science.gov (United States)

    Minardi, S; Molina-Terriza, G; Di Trapani, P; Torres, J P; Torner, L

    2001-07-01

    We experimentally demonstrate the possibility of breaking up intense vortex light beams into stable and controllable sets of parametric solitons. We report observations performed in seeded second-harmonic generation, but the scheme can be extended to all parametric processes. The number of generated solitons is shown to be determined by a robust arithmetic rule.

  16. Vortex Apparatus and Demonstrations

    Science.gov (United States)

    Shakerin, Said

    2010-01-01

    Vortex flow, from millimeter to kilometer in scale, is important in many scientific and technological areas. Examples are seen in water strider locomotion, from industrial pipe flow (wastewater treatment) to air traffic control (safe distance between aircrafts on a runway ready for takeoff) to atmospheric studies. In this paper, we focus on a…

  17. Dynamics of Vortex Cavitation

    NARCIS (Netherlands)

    Pennings, P.C.

    2016-01-01

    This thesis describes the mechanisms with which tip vortex cavitation is responsible for broadband pressure fluctuations on ship propellers. Hypotheses for these are described in detail by Bosschers (2009). Validation is provided by three main cavitation-tunnel experiments, one on a model propeller

  18. Performance analysis of electronic power transformer based on neuro-fuzzy controller.

    Science.gov (United States)

    Acikgoz, Hakan; Kececioglu, O Fatih; Yildiz, Ceyhun; Gani, Ahmet; Sekkeli, Mustafa

    2016-01-01

    In recent years, electronic power transformer (EPT), which is also called solid state transformer, has attracted great interest and has been used in place of the conventional power transformers. These transformers have many important functions as high unity power factor, low harmonic distortion, constant DC bus voltage, regulated output voltage and compensation capability. In this study, proposed EPT structure contains a three-phase pulse width modulation rectifier that converts 800 Vrms AC to 2000 V DC bus at input stage, a dual active bridge converter that provides 400 V DC bus with 5:1 high frequency transformer at isolation stage and a three-phase two level inverter that is used to obtain AC output at output stage. In order to enhance dynamic performance of EPT structure, neuro fuzzy controllers which have durable and nonlinear nature are used in input and isolation stages instead of PI controllers. The main aim of EPT structure with the proposed controller is to improve the stability of power system and to provide faster response against disturbances. Moreover, a number of simulation results are carried out to verify EPT structure designed in MATLAB/Simulink environment and to analyze compensation ability for voltage harmonics, voltage flicker and voltage sag/swell conditions.

  19. On contention resolution in the data vortex optical interconnection network

    Science.gov (United States)

    Shacham, Assaf; Bergman, Keren

    2007-06-01

    Alternative contention resolution techniques are studied in the data vortex interconnection network, namely, the insertion of fiber-delay-line (FDL) buffers into the switching nodes. The performance of each technique is evaluated according to relevant performance metrics: acceptance rate, mean latency, and latency variance. A detailed discussion concludes that while traditional data vortex networks perform better in terms of throughput, FDL-based switching nodes have a favorable impact in reducing the system latency.

  20. Invariant dynamical systems embedded in the N-vortex problem on a sphere with pole vortices

    OpenAIRE

    Sakajo, Takashi

    2006-01-01

    We are concerned with the system of N vortex points on a sphere with two fixed vortex points at the poles. This article gives a reduction method of the system to invariant dynamical systems when all the vortex points have the same strength. It is carried out by considering the invariant property of the system with respect to the shift and pole reversal transformations, for which the polygonal ring configuration of the N vortex points at the line of latitude, called "N-ring",...

  1. Vortex-assisted liquid-liquid-liquid microextraction followed by high performance liquid chromatography for the simultaneous determination of fourteen phenolic acids in honey, iced tea and canned coffee drinks.

    Science.gov (United States)

    Shalash, Marwan; Makahleh, Ahmad; Salhimi, Salizawati Muhamad; Saad, Bahruddin

    2017-11-01

    A vortex-assisted liquid-liquid-liquid microextraction method followed by high performance liquid chromatography-diode array detection for the determination of fourteen phenolic acids (cinnamic, m-coumaric, chlorogenic, syringic, ferulic, o-coumaric, p-coumaric, vanillic, p-hydroxybenzoic, caffeic, 2, 4-dihydroxybenzoic, sinapic, gentisic and gallic acids) in honey, iced tea and canned coffee drink samples has been developed. The separation was achieved using a Poroshell 120-EC-C18 column under a gradient elution at a flow rate of 0.6mLmin-1 and mobile phase composed of methanol and acetic acid (1%, v/v). Under the optimum chromatographic conditions, the fourteen phenolic acids were separated in less than 32min. The extraction was performed using a small volume (400µL) of ternary organic solvents (1-pentanol, propyl acetate and 1-hexanol) dispersed into the aqueous sample (10mL) and assisted by vortex agitation (2500rpm for 45s), the analytes were next back-extracted from the organic solvent using 0.02M KOH (40µL) with vortex speed and time of 2500rpm and 60s, respectively. Under these conditions, enrichment factors of 30-193-fold were achieved. The limits of detection (LODs) were 0.05-0.68µgL-1. Recoveries in honey, iced tea and canned coffee drinks were in the range 72.2-112%. The method was successfully applied for the determination of the phenolic acids in honey, iced tea and canned coffee drinks. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. TRANSFORMATION OF LUDRUK PERFORMANCES: FROM POLITICAL INVOLVEMENT AND STATE HEGEMONY TO CREATIVE SURVIVAL STRATEGY

    Directory of Open Access Journals (Sweden)

    Ikwan Setiawan

    2014-06-01

    Full Text Available This article discusses the transformation of ludruk performances, from Soekarno to Reformation era. In discussing the problem, we apply a cultural studies perspective. From our analysis, there are three findings related to the discursive transformation of ludruk stories. Firstly, in the era of Soekarno, many ludruk groups joined Lembaga Kebudayaan Rakyat (Lekra/Institute of People’s Culture, which had many ideological similarities with Partai Komunis Indonesia (PKI/ Indonesian Communist Party. Consequently, ludruk groups performed some provocative stories that exposed the problems of lower-class people and criticized Islamic religious beliefs. Secondly, after the bloody 1965 tragedy, the regional military apparatuses controlled ludruk groups and their performances, including the stories. In this era, ludruk stories supported the New Order regime’s national development programs and raised people’s consensus on the significance of militarism through popular stories about people’s resistance to colonizers. Thirdly, in the Reformation era, some ludruk groups make newer, interesting stories about many complicated social problems in contemporary society. Finally, we conclude that this mode of transformation through creating newer, social problem-based stories that intertwine with historical conditions has deep historical roots in ludruk performances. In addition, during the Reformation period in whichmarket capitalism becomes a dominant ideology and practice, such newer stories and breakthroughs of staging may become a suitable creative survival strategy for ludruk groups in the midst of techno-cultural popularity as the dominant taste and orientation in societies.

  3. A study of short wave instability on vortex filaments

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hong Yun [Univ. of California, Berkeley, CA (United States)

    1996-12-01

    The numerical stability and accuracy of the vortex method are studied. The effect of the ordinary differential equations (ODE) solver and of the time step on the numerical stability is analyzed. Various ODE solvers are compared and a best performer is chosen. A new constraint on the time step based on numerical stability is proposed and verified in numerical simulations. It is shown through numerical examples that empirical rules for selecting the spatial discretization obtained in simple test problems may not be extended to more general problems. The thin tube vortex filament method is applied to the problem of Widnall's instability on vortex rings. Numerical results different from previous calculations are presented and the source of the discrepancies is explained. The long time behavior of the unstable mode on thin vortex rings is simulated and analyzed. The short wave instability on vortex filaments is investigated both theoretically and numerically. It is shown that the short wave instability always occurs on co-rotating vortex filaments of fixed core structure. Furthermore when they are close to each other, vortex filaments produce short wave unstable modes which lead to wild stretching and folding. However, when the inter-filament distance is large in comparison with the core size of the filaments, unstable modes are bounded by a small fraction of the core size and the vortex filaments do not create hairpins nor wild stretching. These findings may explain the smooth behavior of the superfluid vortices. The formation of hairpin structures on numerical vortex filaments is investigated. It is shown that the formation of hairpin structures is independent of the ODE solver, of the time step and of other numerical parameters. The hairpin structures are primarily caused by short wave instability on co-rotating vortex filaments.

  4. The performance of methods based on the fractional Fourier transform for detecting marine mammal vocalizations.

    Science.gov (United States)

    Locke, Jonathan; White, Paul R

    2011-10-01

    The analysis of cetacean vocalizations is considered using Fourier-based techniques that employ chirp functions in their decomposition. In particular, the paper considers a short-time methods based on the fractional Fourier transform for detecting frequency modulated narrow-band signals, such as dolphin whistles, and compares this to the classical short-time Fourier methods. The fractional Fourier technique explored computes transforms associated with a range of chirp rates and automatically selects the rate for the final analysis. This avoids the need for prior knowledge of signal's chirp rate. An analysis is presented that details the performance of both methods as signal detectors and allows one to determine their detection thresholds. These thresholds are then used to measure the detectability of synthetic signals. This principle is then extended to measure performance on a set of recordings of narrow-band vocalizations from a range of cetacean species. © 2011 Acoustical Society of America

  5. Thermonuclear Quenching in Flame-Vortex Interactions

    Science.gov (United States)

    Zingale, M.; Niemeyer, J. C.; Timmes, F. X.; Dursi, L. J.; Calder, A. C.; Fryxell, B.; Olson, K.; Ricker, P.; Rosner, R.; Truran, J. W.; Tufo, H.; MacNeice, P.

    2000-12-01

    A Type Ia supernova begins as a flame, deep in the interior of a white dwarf. At some point, the burning may undergo a deflagration-detonation transition (DDT). Some mechanisms for this transition require a preconditioned region in the star. As the flame propagates down the temperature gradient, the speed increases, and the transition to a detonation may occur (see Khokhlov et al. 1997; Niemeyer & Woosley 1997). For this to happen, the region must be free of any temperature fluctuations -- any burning must be quenched. We show direct numerical simulations of flame-vortex interactions in order to understand quenching of thermonuclear flames. The key question is -- can a thermonuclear flame be quenched? If not, the DDT mechanisms that demand the finely tuned preconditioned region are unlikely to work. In these simulations, we pass a steady-state laminar flame through a vortex pair. The vortex pair represents the most severe strain the flame front will encounter inside the white dwarf. We perform a parameter study, varying the speed and size of the vortex pair, in order to understand the quenching process. These simulations were carried out with the FLASH Code. This work is supported by the Department of Energy under Grant No. B341495 to the Center for Astrophysical Thermonuclear Flashes at the University of Chicago. These calculations were performed on the Nirvana Cluster at Los Alamos National Laboratory

  6. Performance Improvement of Sensorless Vector Control for Matrix Converter Drives Using PQR Transformation

    DEFF Research Database (Denmark)

    Lee, Kyo-Beum; Blaabjerg, Frede

    2005-01-01

    This paper presents a new method to improve sensorless performance of matrix converter drives using PQR power transformation. The non-linearity of matrix converter drives such as commutation delay, turn-on and turn-off time of switching device, and on-state switching device voltage drop is modelled...... drives using a 3 kW matrix converter system without a speed sensor. Experimental results are shown to illustrate the feasibility of the proposed strategy....

  7. The impact of dimensions of transformational leadership on post-acquisition performance of acquired company

    OpenAIRE

    Sladjana Savovic

    2017-01-01

    Mergers and acquisitions (M&A) are the important mechanisms through which companies can achieve growth, gain access to new markets and diversify their activities. Although companies engage themselves in M&As with optimism, empirical evidence shows that many M&A transactions are not successful. Therefore, research is often focused on the identification of the ways to improve post-acquisition performance. One of the key success factors of M&A is to provide adequate transformational leadership d...

  8. The Relationship between Transformational Leadership and Followers’ Work Characteristics and Task Performance

    OpenAIRE

    Oon Fok-Yew

    2015-01-01

    Although leaders and followers are both essential elements within the leadership process, there has been limited research regarding followers and their effects in the process. This study aims to examine the relationship between transformational leadership and followers’ work characteristics and performance, and follower’s attitudes towards a leader as a moderating variable. A questionnaire survey will be used to collect data from Malaysian multi-national corporations. The questionnaire will b...

  9. Segmented trapped vortex cavity

    Science.gov (United States)

    Grammel, Jr., Leonard Paul (Inventor); Pennekamp, David Lance (Inventor); Winslow, Jr., Ralph Henry (Inventor)

    2010-01-01

    An annular trapped vortex cavity assembly segment comprising includes a cavity forward wall, a cavity aft wall, and a cavity radially outer wall there between defining a cavity segment therein. A cavity opening extends between the forward and aft walls at a radially inner end of the assembly segment. Radially spaced apart pluralities of air injection first and second holes extend through the forward and aft walls respectively. The segment may include first and second expansion joint features at distal first and second ends respectively of the segment. The segment may include a forward subcomponent including the cavity forward wall attached to an aft subcomponent including the cavity aft wall. The forward and aft subcomponents include forward and aft portions of the cavity radially outer wall respectively. A ring of the segments may be circumferentially disposed about an axis to form an annular segmented vortex cavity assembly.

  10. Performance analysis of a finite radon transform in OFDM system under different channel models

    Energy Technology Data Exchange (ETDEWEB)

    Dawood, Sameer A.; Anuar, M. S.; Fayadh, Rashid A. [School of Computer and Communication Engineering, Universiti Malaysia Perlis (UniMAP) Pauh Putra, 02000 Arau, Parlis (Malaysia); Malek, F.; Abdullah, Farrah Salwani [School of Electrical System Engineering, Universiti Malaysia Perlis (UniMAP) Pauh Putra, 02000 Arau, Parlis (Malaysia)

    2015-05-15

    In this paper, a class of discrete Radon transforms namely Finite Radon Transform (FRAT) was proposed as a modulation technique in the realization of Orthogonal Frequency Division Multiplexing (OFDM). The proposed FRAT operates as a data mapper in the OFDM transceiver instead of the conventional phase shift mapping and quadrature amplitude mapping that are usually used with the standard OFDM based on Fast Fourier Transform (FFT), by the way that ensure increasing the orthogonality of the system. The Fourier domain approach was found here to be the more suitable way for obtaining the forward and inverse FRAT. This structure resulted in a more suitable realization of conventional FFT- OFDM. It was shown that this application increases the orthogonality significantly in this case due to the use of Inverse Fast Fourier Transform (IFFT) twice, namely, in the data mapping and in the sub-carrier modulation also due to the use of an efficient algorithm in determining the FRAT coefficients called the optimal ordering method. The proposed approach was tested and compared with conventional OFDM, for additive white Gaussian noise (AWGN) channel, flat fading channel, and multi-path frequency selective fading channel. The obtained results showed that the proposed system has improved the bit error rate (BER) performance by reducing inter-symbol interference (ISI) and inter-carrier interference (ICI), comparing with conventional OFDM system.

  11. Phase transformation in thiamine hydrochloride tablets: Influence on tablet microstructure, physical properties, and performance.

    Science.gov (United States)

    Chakravarty, Paroma; Suryanarayanan, Raj; Govindarajan, Ramprakash

    2012-04-01

    The objective of this article was to monitor phase transformation in thiamine hydrochloride, from a nonstoichiometric hydrate (NSH) to a hemihydrate (HH), in stored tablets, prepared both by direct compression and wet granulation, and to relate the storage-induced phase transformation with changes in tablet microstructure, physical properties, and performance. Raman spectroscopy revealed complete NSH → HH transformation in tablets, within 30 h of storage at 40°C/75% relative humidity. When the tablets were prepared by wet granulation of NSH alone, there was a marked increase in both tablet volume and hardness on storage. However, when microcrystalline cellulose (MCC) was included in granulation, the resulting stored tablets also exhibited a pronounced increase in disintegration time. In contrast, tablets prepared by dry processing via compression of a NSH-MCC physical mixture did not exhibit any changes in properties, despite the in situ solid form conversion. Scanning electron microscopy revealed growth of needle-like HH crystals in all stored tablets and mercury porosimetry revealed considerable changes in the pore size distribution during storage. Longer storage led to crystal growth (Ostwald ripening), causing further gradual but less dramatic changes in properties. The phase transformation and the complex interparticulate associations in the tablet influenced the changes in tablet microstructure, compact physical properties, and product behavior. Copyright © 2011 Wiley Periodicals, Inc.

  12. Comparison between hydraulic and structural based anti-vortex methods at intakes

    Science.gov (United States)

    Monshizadeh, Morteza; Tahershamsi, Ahmad; Rahimzadeh, Hassan; Sarkardeh, Hamed

    2017-08-01

    Surface vortices are the main reason of flow instability and entraining air and debris into the intakes. Using structural based anti-vortex facilities is a common method for dissipating vortices over the intakes. In the present experimental study, performance of a new hydraulic based anti-vortex method is compared with available structural based anti-vortex methods over the horizontal intakes. In the new approach dynamically high-risk surface vortices are eliminated by imposing a hydraulic jet at the formed vortex zone over the intake. The injected jet acts as a point source of external momentum in order to change the hydrodynamic condition of the formed vortex flow. Results show that the investigated hydraulic based anti-vortex device is more flexible and more hydraulically efficient than the structural based anti-vortex methods, especially when the intake Froude number is higher than 1.3.

  13. Multiplexing of adjacent vortex modes with the forked grating coupler

    Science.gov (United States)

    Nadovich, Christopher T.; Kosciolek, Derek J.; Crouse, David T.; Jemison, William D.

    2017-08-01

    For vortex fiber multiplexing to reach practical commercial viability, simple silicon photonic interfaces with vortex fiber will be required. These interfaces must support multiplexing. Toward this goal, an efficient singlefed multimode Forked Grating Coupler (FGC) for coupling two different optical vortex OAM charges to or from the TE0 and TE1 rectangular waveguide modes has been developed. A simple, apodized device implemented with e-beam lithography and a conventional dual-etch processing on SOI wafer exhibits low crosstalk and reasonable mode match. Advanced designs using this concept are expected to further improve performance.

  14. A multiresolution remeshed Vortex-In-Cell algorithm using patches

    DEFF Research Database (Denmark)

    Rasmussen, Johannes Tophøj; Cottet, Georges-Henri; Walther, Jens Honore

    2011-01-01

    We present a novel multiresolution Vortex-In-Cell algorithm using patches of varying resolution. The Poisson equation relating the fluid vorticity and velocity is solved using Fast Fourier Transforms subject to free space boundary conditions. Solid boundaries are implemented using the semi...

  15. Superconducting Vortex with Antiferromagnetic Core

    Energy Technology Data Exchange (ETDEWEB)

    Arovas, D.P. [Department of Physics, University of California at San Diego, La Jolla, California 92093 (United States); Berlinsky, A.J.; Kallin, C.; Zhang, S. [Department of Physics, Stanford University, Stanford, California 94305 (United States)

    1997-10-01

    We show that a superconducting vortex in underdoped high T{sub c} superconductors could have an antiferromagnetic core. This type of vortex configuration arises as a topological solution in the recently constructed SO(5) nonlinear {sigma} model and in Landau-Ginzburg theory with competing antiferromagnetic and superconducting order parameters. Experimental detection of this type of vortex by muon spin resonance and neutron scattering is proposed. {copyright} {ital 1997} {ital The American Physical Society}

  16. The roles of emotional intelligence, interpersonal skill, and transformational leadership on improving construction safety performance

    Directory of Open Access Journals (Sweden)

    Riza Yosia Sunindijo

    2013-09-01

    Full Text Available Due to the characteristics of the constructionindustry, human skills are essential for working with and through others inmanaging safety. Research has shown that emotional intelligence, interpersonalskill, and transformational leadership are human skill components that generatesuperior performance in today’s workplace. The aim of this research is toinvestigate the influence of project management personnel’s human skills on theimplementation of safety management tasks and development of safety climate inconstruction projects. The structural equation modelling (SEM method wasapplied to analyse the quantitative data collected and establishinterrelationship among the research variables. The results indicate thatemotional intelligence is a key factor for developing interpersonal skill andtransformational leadership, and for implementing safety management tasks whichleads to the development of safety climate. This research also found thatinterpersonal skill is needed for becoming transformational leaders whocontribute to the development of safety climate.

  17. Vortex-assisted low density solvent liquid-liquid microextraction and salt-induced demulsification coupled to high performance liquid chromatography for the determination of five organophosphorus pesticide residues in fruits.

    Science.gov (United States)

    Seebunrueng, Ketsarin; Santaladchaiyakit, Yanawath; Srijaranai, Supalax

    2015-01-01

    A simple and rapid microextraction method, vortex-assisted low density solvent liquid-liquid microextraction and salt-induced demulsification (VLLME-SID) coupled to high performance liquid chromatography (HPLC) was developed for the determination of organophosphorus pesticide (OPP) residues in fruits. The studied OPPs were azinphos-methyl, parathion-methyl, fenitrothion, diazinon and chlorpyrifos. For VLLME-SID, a mixture of low density solvents (1-dodecanol and hexane) was used as the extraction solvent under vortex agitation for enhancing dispersion. After complete dispersion, the emulsion was formed and the OPPs were extracted into extraction solvent droplets. Then, the emulsion was quickly broken up into two clear phases after the addition of AlCl3 as a demulsifier. Centrifugation was not required in this procedure. Under the optimal conditions, high enrichment factors (180-282), low limit of detections (LODs) (0.05-1 ng mL(-1)) and good precision (RSD≤7% for retention time and peak area) were obtained. The proposed method was successfully applied to the analysis of OPP residues in fruit samples (watermelon, grape, and cantaloupe). The LODs for samples were in the range 0.0006-0.0015 mg kg(-1) which are below the established EU-MRLs (0.01-0.3 mg kg(-1)). Good recoveries were also obtained (80-104%). Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Aircraft Wake Vortex Deformation in Turbulent Atmosphere

    OpenAIRE

    Hennemann, Ingo; Holzaepfel, Frank

    2007-01-01

    Large-scale distortion of aircraft wake vortices appears to play a crucial role for aircraft safety during approach and landing. Vortex distortion is investigated based on large eddy simulations of wake vortex evolution in a turbulent atmosphere. A vortex identification method is developed that can be adapted to the vortex scales of interest. Based on the identified vortex center tracks, a statistics of vortex curvature radii is established. This statistics constitutes the basis for understan...

  19. Performance of single wire earth return transformers with amorphous alloy core in a rural electric energy distribution system

    Directory of Open Access Journals (Sweden)

    Benedito Antonio Luciano

    2012-10-01

    Full Text Available In this paper are presented some considerations about the performance of single wire earth return amorphous alloy core transformers in comparison with conventional silicon steel sheets cores transformers used in rural electric energy distribution network. It has been recognized that amorphous metal core transformers improve electrical power distribution efficiency by reducing transformer core losses. This reduction is due to some electromagnetic properties of the amorphous alloys such as: high magnetic permeability, high resistivity, and low coercivity. Experimental results obtained with some single-phase, 60 Hz, 5 kVA amorphous core transformers installed in a rural area electric distribution system in Northern Brazil have been confirming their superior performance in comparison to identical nominal rated transformers built with conventional silicon steel cores, particularly with regard to the excitation power and to the no-load losses.

  20. Performance analysis of wavelet transforms and morphological operator-based classification of epilepsy risk levels

    Science.gov (United States)

    Harikumar, Rajaguru; Vijayakumar, Thangavel

    2014-12-01

    The objective of this paper is to compare the performance of singular value decomposition (SVD), expectation maximization (EM), and modified expectation maximization (MEM) as the postclassifiers for classifications of the epilepsy risk levels obtained from extracted features through wavelet transforms and morphological filters from electroencephalogram (EEG) signals. The code converter acts as a level one classifier. The seven features such as energy, variance, positive and negative peaks, spike and sharp waves, events, average duration, and covariance are extracted from EEG signals. Out of which four parameters like positive and negative peaksand spike and sharp waves, events and average duration are extracted using Haar, dB2, dB4, and Sym 8 wavelet transforms with hard and soft thresholding methods. The above said four features are also extracted through morphological filters. Then, the performance of the code converter and classifiers are compared based on the parameters such as performance index (PI) and quality value (QV).The performance index and quality value of code converters are at low value of 33.26% and 12.74, respectively. The highest PI of 98.03% and QV of 23.82 are attained at dB2 wavelet with hard thresholding method for SVD classifier. All the postclassifiers are settled at PI value of more than 90% at QV of 20.

  1. Characterising stationary and translating vortex flow using magnetic resonance

    Science.gov (United States)

    Vallatos, Antoine; Wilson, Mark C. T.; Taylor, Annette F.; Britton, Melanie M.

    2012-09-01

    We report magnetic resonance (MR) velocity and diffusion maps in three directions for stationary vortices (Taylor vortex flow —TVF) and velocity maps for translating vortices (vortex flow reactor —VFR) produced in a Couette cell. Motion artefacts in the translating vortex flow are removed by synchronising data acquisition with the translation period of the vortices. MR propagator experiments, which measure the conditional probability density for displacement, were performed to characterise molecular displacements in these systems. Simulations were performed using the experimental velocity and diffusion maps to aid interpretation of experimentally measured propagators and enable characterisation of the macro-mixing and transport properties within TVF and VFR systems. These simulations enabled molecular transport and mixing to be assessed over longer-time scales than are accessible experimentally, allowing plug flow, by-pass flow and inter-vortex mixing to be quantified.

  2. Investigation a single-spiral vortex in a swirl flow

    Directory of Open Access Journals (Sweden)

    Gesheva Elizaveta S.

    2017-01-01

    Full Text Available The work is aimed at a detailed study of large-scale helical vortex structures emerging in a high turbulent intensively swirling flow. It was shown that the vortex formed in the chamber by installing diaphragm with shifted outlet is folded into a single-helical vortex. The flow visualization shows that although the vortex axis performs slow oscillations (precession, on average this structure is fixed in space. The velocity fields were measured with the aid of a nonintrusive method of flow diagnostics (PIV. Verification of the calculation results obtained using a LES simulation was performed based on measured experimental data to confirm the correctness of the chosen mathematical modelling approach. It has been asserted that the investigated regimes are in a self-similarity area relative to Reynolds number.

  3. Melting of heterogeneous vortex matter: The vortex 'nanoliquid'

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 66; Issue 1. Melting of heterogeneous vortex matter: The vortex ... By sweeping the applied magnetic field, the number of vortices in the nanodroplets is varied continuously from a few to several hundred. Upon cooling, the caged nanodroplets freeze into ordered ...

  4. Vortex-Surface Interactions: Vortex Dynamics and Instabilities

    Science.gov (United States)

    2015-10-16

    Crow instability (see for example Leweke & Williamson, 2012). (b) Short-wave cooperative elliptic instability (Leweke & Williamson 1998). (c...vortex generators. Of interest in such studies would be the formation of secondary vorticity from the surface, the downstream vortex trajectories , and

  5. Large-scale vortex structures and local heat release in lean turbulent swirling jet-flames under vortex breakdown conditions

    Science.gov (United States)

    Chikishev, Leonid; Lobasov, Aleksei; Sharaborin, Dmitriy; Markovich, Dmitriy; Dulin, Vladimir; Hanjalic, Kemal

    2017-11-01

    We investigate flame-flow interactions in an atmospheric turbulent high-swirl methane/air lean jet-flame at Re from 5,000 to 10,000 and equivalence ratio below 0.75 at the conditions of vortex breakdown. The focus is on the spatial correlation between the propagation of large-scale vortex structures, including precessing vortex core, and the variations of the local heat release. The measurements are performed by planar laser-induced fluorescence of hydroxyl and formaldehyde, applied simultaneously with the stereoscopic particle image velocimetry technique. The data are processed by the proper orthogonal decomposition. The swirl rate exceeded critical value for the vortex breakdown resulting in the formation of a processing vortex core and secondary helical vortex filaments that dominate the unsteady flow dynamics both of the non-reacting and reacting jet flows. The flame front is located in the inner mixing layer between the recirculation zone and the annular swirling jet. A pair of helical vortex structures, surrounding the flame, stretch it and cause local flame extinction before the flame is blown away. This work is supported by Russian Science Foundation (Grant No 16-19-10566).

  6. Linking transformational leadership to nurses' extra-role performance: the mediating role of self-efficacy and work engagement.

    Science.gov (United States)

    Salanova, Marisa; Lorente, Laura; Chambel, Maria J; Martínez, Isabel M

    2011-10-01

    This paper is a report of a social cognitive theory-guided study about the link between supervisors' transformational leadership and staff nurses' extra-role performance as mediated by nurse self-efficacy and work engagement. Past research has acknowledged the positive influence that transformational leaders have on employee (extra-role) performance. However, less is known about the psychological mechanisms that may explain the links between transformational leaders and extra-role performance, which encompasses behaviours that are not considered formal job requirements, but which facilitate the smooth functioning of the organization as a social system. Seventeen supervisors evaluated nurses' extra-role performance, the data generating a sample consisting of 280 dyads. The nurses worked in different health services in a large Portuguese hospital and the participation rate was 76·9% for nurses and 100% for supervisors. Data were collected during 2009. A theory-driven model of the relationships between transformation leadership, self-efficacy, work engagement and nurses' extra-role performance was tested using Structural Equation Modelling. Data analysis revealed a full mediation model in which transformational leadership explained extra-role performance through self-efficacy and work engagement. A direct relationship between transformational leadership and work engagement was also found. Nurses' supervisors with a transformational leadership style enhance different 'extra-role' performance in nurses and this increases hospital efficacy. They do so by establishing a sense of self-efficacy but also by amplifying their levels of engagement in the workplace. © 2011 Blackwell Publishing Ltd.

  7. Optical vortex filtering for the detection of Electromagnetically Induced Transparency

    OpenAIRE

    Phillips, Nathaniel B.; Romanov, Gleb V.; Ames, William F.; Novikova, Irina

    2009-01-01

    We report the realization of an optical filter based on an optical vortex mask designed to exclusively detect a weak coherent laser field in the presence of much stronger spatially-overlapping field. We demonstrate the performance of such an optical vortex filter to eliminate the strong control field and detect only a weak optical field's transmission under the conditions of electromagnetically induced transparency. The attractive feature of such filter is its insensitivity to optical field f...

  8. Transforming Pristine Carbon Fiber Tows into High Performance Solid-State Fiber Supercapacitors.

    Science.gov (United States)

    Yu, Dingshan; Zhai, Shengli; Jiang, Wenchao; Goh, Kunli; Wei, Li; Chen, Xudong; Jiang, Rongrong; Chen, Yuan

    2015-09-02

    A facile activation strategy can transform pristine carbon fiber tows into high-performance fiber electrodes with a specific capacitance of 14.2 F cm(-3) . The knottable fiber supercapacitor shows an energy density of 0.35 mW h cm(-3) , an ultrahigh power density of 3000 mW cm(-3) , and a remarkable capacitance retention of 68%, when the scan rate increases from 10 to 1000 mV s(-1) . © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. The Acoustically Driven Vortex Cannon

    Science.gov (United States)

    Perry, Spencer B.; Gee, Kent L.

    2014-01-01

    Vortex cannons have been used by physics teachers for years, mostly to teach the continuity principle. In its simplest form, a vortex cannon is an empty coffee can with a hole cut in the bottom and the lid replaced. More elaborate models can be purchased through various scientific suppliers under names such as "Air Cannon" and…

  10. Characterizing the dynamic property of the vortex tail in a gas cyclone by wall pressure measurements

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Cuizhi; Sun, Guogang; Dong, Ruiqian; Fu, Shuangcheng [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing, 102249 (China)

    2010-08-15

    To explore a determination method for cyclone vortex tail, the wall pressures at different axial and radial positions of a cylinder-on-cone cyclone were measured and analyzed by the Fast Fourier Transform (FFT) and probability density analyses in this paper. The cyclone vortex tail was also visualized by a red ink tracer. The results show that the cyclone wall pressure does not change in the cylindrical section and gradually decreases in the conical section. The magnitudes of wall pressure at different azimuths are almost identical, indicating an axisymmetrical wall pressure radial profile in these parts of the cyclone. Whereas in the lower part of the cone and/or the upper part of dipleg, there is a sudden fall of wall pressure and non-axisymmetrical pressure radial profile. The minimum wall pressure occurs at about 270 azimuth in this region. Underneath in the next part of the dipleg, the wall pressure rapidly rises and returns to axisymmetry. These characteristics indicate that the vortex tail is bended to wall, turns around in this region, and can be used as evidences of the vortex tail. The position determined by the pressure measurement is close to the position of the rotating ring observed in the tracing experiment. It is also found that the frequency of the inner vortex is different from that of the outer vortex. The inner vortex flow fluctuates stronger and faster than its outer partner. At the vortex tail zone, the vortex breaks and the inner vortex fluctuation is involved in the wall pressure signal. Therefore, the position and dynamic property of the vortex tail can be well identified from the wall pressure measurement. The pressure measurement could provide some solid experimental basis for assessing relations of natural vortex length. (author)

  11. Instability of vortex pair leapfrogging

    DEFF Research Database (Denmark)

    Tophøj, Laust; Aref, Hassan

    2013-01-01

    Leapfrogging is a periodic solution of the four-vortex problem with two positive and two negative point vortices all of the same absolute circulation arranged as co-axial vortex pairs. The set of co-axial motions can be parameterized by the ratio 0 vortex pair sizes at the time when one...... pair passes through the other. Leapfrogging occurs for α > σ2, where is the silver ratio. The motion is known in full analytical detail since the 1877 thesis of Gröbli and a well known 1894 paper by Love. Acheson ["Instability of vortex leapfrogging," Eur. J. Phys.21, 269-273 (2000...... pairs fly off to infinity, and a "walkabout" mode, where the vortices depart from leapfrogging but still remain within a finite distance of one another. We show numerically that this transition is more gradual, a result that we relate to earlier investigations of chaotic scattering of vortex pairs [L...

  12. OWC with vortex beams in data center networks

    Science.gov (United States)

    Kupferman, Judy; Arnon, Shlomi

    2017-10-01

    Data centers are a key building block in the rapidly growing area of internet technology. A typical data center has tens of thousands of servers, and communication between them must be flexible and robust. Vortex light beams have orbital angular momentum and can provide a useful and flexible method for optical wireless communication in data centers. Vortex beams can be generated with orbital angular momentum but independent of polarization, and used in a multiplexed system. We propose a multiplexing vortex system to increase the communication capacity using optical wireless communication for data center networks. We then evaluate performance. This paper is intended for use as an engineering guideline for design of vortex multiplexing in data center applications.

  13. Positive Institutions and their relationship with transformational leadership, empathy and team performance

    Directory of Open Access Journals (Sweden)

    Jessica Solares Menegazzo

    2015-09-01

    Full Text Available The current study tests the relationship between transformational leadership, empathy and excellent team performance, based on the HEalthy & Resilient Organizations (HERO Model (Salanova, Llorens, Cifre & Martínez, 2012 in positive institutions, the third pillar of positive psychology (Seligman & Csikszentmihalyi, 2000. The study of empathy and its role in companies is important because it is not yet widely known the benefits that can provide to any institution. The study attempt to show a full mediating role of empathy in this relationship. The sample consist on  69 work teams, from 7 Small -and Medium- sized Enterprises (SMEs including 4 educational institutions and 3 institutions of medical services from Spain. The Interclass Correlation Coefficients (ICC1 and ICC2 and the Average Deviation Index (ADM(J supports data aggregation at the team level. The results using SEM, through work teams, supported the hypothesis, that is, the empathy plays a full mediating role between transformational leadership and excellent team performance. Finally, theoretical and practical implications of the results are discussed.

  14. Low Head, Vortex Induced Vibrations River Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Bernitsas, Michael B.; Dritz, Tad

    2006-06-30

    Vortex Induced Vibrations Aquatic Clean Energy (VIVACE) is a novel, demonstrated approach to extracting energy from water currents. This invention is based on a phenomenon called Vortex Induced Vibrations (VIV), which was first observed by Leonardo da Vinci in 1504AD. He called it ‘Aeolian Tones.’ For decades, engineers have attempted to prevent this type of vibration from damaging structures, such as offshore platforms, nuclear fuel rods, cables, buildings, and bridges. The underlying concept of the VIVACE Converter is the following: Strengthen rather than spoil vortex shedding; enhance rather than suppress VIV; harness rather than mitigate VIV energy. By maximizing and utilizing this unique phenomenon, VIVACE takes this “problem” and successfully transforms it into a valuable resource for mankind.

  15. Comment on "Generating a perfect quantum optical vortex"

    Science.gov (United States)

    Barral, David; Liñares, Jesús

    2017-10-01

    In a recent article, Banerji et al. introduced a novel quantum state of light, coined as the perfect quantum optical vortex state [Phys. Rev. A 94, 053838 (2016), 10.1103/PhysRevA.94.053838] due to its mathematical similarity with the classical perfect vortex beam. This state is obtained by means of the Fourier transform of a Bessel-Gaussian vortex state, and the authors claim that this can be accomplished by means of a simple lens. Here, we will show that this statement is wrong since a lens cannot modify the quantum noise distribution related to the input optical quantum state and this has to be exchanged by an "effective lens."

  16. Transport velocity transformation - A convenient method for performance analysis of multilayer solar cell structure

    Science.gov (United States)

    Wolf, M.

    1981-01-01

    It is noted that in the case of low-level injection, space-charge quasi-neutrality, and spatially constant material parameters (including an electrostatic field), the individual layer can be treated analytically and the basic solar cell performance parameters can be evaluated from three equations. The first equation represents the transformation of the transport velocity across the layer from the other layer boundary. The second establishes the light-generated current output from the layer interface, under the influence of the transport velocities and minority-carrier density at both layer boundaries and of bulk recombination. The third equation describes the flow of these carriers across other layers. The power of the approach is considered to lie in its facility for analysis of the solar cell's performance layer by layer, giving a clear picture of the individual layer's influence on cell efficiency.

  17. Strategic Innovation for Business Performance: The Art and Science of Transformation

    Directory of Open Access Journals (Sweden)

    Harold Schroeder

    2013-09-01

    Full Text Available Despite the well-documented association between innovation and business performance, many organizations struggle in their attempts to become successful innovators. This article discusses a recommended “art and science of transformation” approach to help companies improve their innovation performance through effective organizational change. The approach is focused on four key factors: culture, collaboration, strategy, and systems. Examples are drawn from a review of previous research to demonstrate successful innovation practice using similar approaches, and examples of less successful practice are included to highlight ways in which an "art and science" approach can help overcome the difficulties often faced. The article concludes with some practical, step-by-step guidance based on the art and science of transformation framework.

  18. High Performance Discrete Cosine Transform Operator Using Multimedia Oriented Subword Parallelism

    Directory of Open Access Journals (Sweden)

    Shafqat Khan

    2015-01-01

    Full Text Available In this paper an efficient two-dimensional discrete cosine transform (DCT operator is proposed for multimedia applications. It is based on the DCT operator proposed in Kovac and Ranganathan, 1995. Speed-up is obtained by using multimedia oriented subword parallelism (SWP. Rather than operating on a single pixel, the SWP-based DCT operator performs parallel computations on multiple pixels packed in word size input registers so that the performance of the operator is increased. Special emphasis is made to increase the coordination between pixel sizes and subword sizes to maximize resource utilization rate. Rather than using classical subword sizes (8, 16, and 32 bits, multimedia oriented subword sizes (8, 10, 12, and 16 bits are used in the proposed DCT operator. The proposed SWP DCT operator unit can be used as a coprocessor for multimedia applications.

  19. Vortex-vortex interactions in toroidally trapped Bose-Einstein condensates

    OpenAIRE

    Schulte, T.; Santos, L.; Sanpera, A.; M. Lewenstein

    2002-01-01

    We analyze the vortex dynamics and vortex-vortex interactions in Bose-Einstein condensates confined in toroidal traps. We show that this particular geometry strongly distorts the vortex dynamics. The numerically calculated vortex trajectories are well explained by an analytical calculation based on image method and conformal mapping. Finally, the dissipation effects are discussed.

  20. Cylindrical vortex wake model: right cylinder

    DEFF Research Database (Denmark)

    Branlard, Emmanuel; Gaunaa, Mac

    2015-01-01

    The vortex system consisting of a bound vortex disk, a root vortex and a vortex cylinder as introduced by Joukowski in 1912 is further studied in this paper. This system can be used for simple modeling of rotors (e.g. wind turbines) with infinite number of blades and finite tip-speed ratios. For ...

  1. A model for description of the pressure field on a plate as the vortex ring passes

    Science.gov (United States)

    Kuibin, P. A.

    2017-11-01

    During recent experimental research a phenomenon of vortex reconnection between coils of helical-like vortex in expanding cone was revealed. Two different scenarios of the reconnection were recorded with high speed video camera. In one case a vortex ring linked with the main helical-like vortex was observed. In another case the vortex ring was found to separate from the main vortex. After separation the vortex ring moves by spiral trajectory approaching the channel wall. The subsequent experiments with synchronization of the video recording with measurements of the pressure on the channel wall revealed intense pressure pulses as the vortex ring passed near the probe. In the present work we develop an analytical model for describing the pressure pulses arising when the vortex ring passes along surface. For simplicity we consider a flat surface rather than a conical one. The performed analysis yielded the pressure distributions on the surface in dependence on the specified parameters. The most important parameter that determines the form of pressure peaks is the minimum distance from the vortex to the surface. Variation of the angles of inclination of the ring plane provides fundamentally different pulse shapes.

  2. Manipulation of vortex rings for flow control

    Energy Technology Data Exchange (ETDEWEB)

    Toyoda, Kuniaki; Hiramoto, Riho [Mechanical Systems Engineering, Hokkaido Institute of Technology, Maeda 7-15-4-1, Teine-ku, Sapporo 006-855 (Japan)], E-mail: toyodahm@poppy.ocn.ne.jp

    2009-10-15

    This paper reviews the dynamics of vortex rings and the control of flow by the manipulation of vortex rings. Vortex rings play key roles in many flows; hence, the understanding of the dynamics of vortex rings is crucial for scientists and engineers dealing with flow phenomena. We describe the structures and motions of vortex rings in circular and noncircular jets, which are typical examples of flows evolving into vortex rings. For circular jets the mechanism of evolving, merging and breakdown of vortex rings is described, and for noncircular jets the dynamics of three-dimensional deformation and interaction of noncircular vortex rings under the effect of self- and mutual induction is discussed. The application of vortex-ring manipulation to the control of various flows is reviewed with successful examples, based on the relationship between the vortex ring dynamics and the flow properties. (invited paper)

  3. Vortex Anemometer Using MEMS Cantilever Sensor

    CERN Document Server

    Zylka, P; Zylka, Pawel; Modrzynski, Pawel

    2010-01-01

    This paper presents construction and performance of a novel hybrid microelectromechanical system (MEMS) vortex flowmeter. A miniature cantilever MEMS displacement sensor was used to detect frequency of vortices development. 3-mm-long silicon cantilever, protruding directly out of a trailing edge of a trapezoidal glass-epoxy composite bluff body was put into oscillatory motion by vortices shed alternately from side surfaces of the obstacle. Verified linearmeasurement range of the device extended from 5 to 22 m/s; however, it could be broadened in absence of external 50-Hz mains electrical interfering signal which required bandpass frequency-domain digital sensor signal processing. The MEMS vortex sensor proved its effectiveness in detection of semilaminar airflow velocity distribution in a 40-mm-diameter tubular pipe.

  4. Best Practices in the Performing Arts: Transformation and Flourishing in a Progressive Summer Dance Theater Program for Adolescents

    Science.gov (United States)

    Kane, Kevin M.

    2013-01-01

    The idea of "best practices" in the performing arts is introduced as a set of progressive educational values and pedagogical strategies that attempt to not only train youth in the performing arts, but also to be transformative. This article builds on the work of educational reformer John Dewey to describe progressive performing arts…

  5. Phenomenological Model of Vortex Generators

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver; Westergaard, C.

    1995-01-01

    For some time attempts have been made to improve the power curve of stall regulated wind turbines by using devices like vortex generators VG and Gurney flaps. The vortex produces an additional mixing of the boundary layer and the free stream and thereby increasing the momentum close to the wall......, which again delays separation in adverse pressure gradient regions. A model is needed to include the effect of vortex generators in numerical computations of the viscous flow past rotors. In this paper a simple model is proposed....

  6. Distribution transformer with automatic voltage adjustment - performance; Transformador de distribucion con ajuste automatico de tension - desempeno

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez Ruiz, Gustavo A.; Delgadillo Bocanegra, Alfonso; Betancourt Ramirez, Enrique [PROLEC-GE, Apodaca, Nuevo Leon (Mexico)]. E-mail: gustavo1.hernandez@ge.com; alfonso.delgadillobocanegra@ge.com; enrique.betancourt@ge.com; Ramirez Arredondo, Juan M. [CINVESTAV-Guadalajara, Zapopan, Jalisco (Mexico)]. E-mail: jramirez@gdl.cinvestav.mx

    2010-11-15

    In the electric power distribution systems, the power quality is strongly linked with the service stability voltage. In the radial kind systems, it is virtually impossible to achieve a flat voltage along the lines, so it is desirable to count with transformers that can adjust automatically the turns ratio. In this work, it is described the development and the performance of a transformer with an integrated electronic tap changer, that allows to change the turns ratio along the standard range of +/-5%, and it was identified the application limits of the technology. [Spanish] En los sistemas de distribucion de energia electrica, la calidad del suministro de energia esta fuertemente ligada con la estabilidad del voltaje de servicio. En sistemas de tipo radial, es virtualmente imposible mantener uniforme la tension a lo largo de las lineas, por lo que se hace deseable contar con transformadores que puedan ajustar automaticamente la relacion de transformacion. En este trabajo, se describe el desarrollo y desempeno de un transformador con switch electronico integrado, que permite variar la relacion de transformacion dentro del rango estandarizado de +/-5%, y se identifican los limites de aplicacion de la tecnologia.

  7. Multiple helical modes of vortex breakdown

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær; Naumov, I. V.; Okulov, Valery

    2011-01-01

    Experimental observations of vortex breakdown in a rotating lid-driven cavity are presented. The results show that vortex breakdown for cavities with high aspect ratios is associated with the appearance of stable helical vortex multiplets. By using results from stability theory generalizing Kelvin......’s problem on vortex polygon stability, and systematically exploring the cavity flow, we succeeded in identifying two new stable vortex breakdown states consisting of triple and quadruple helical multiplets....

  8. Vortex electronis and squids

    CERN Document Server

    2003-01-01

    Understanding the nature of vortices in high-Tc superconductors is a crucial subject for research on superconductive electronics, especially for superconducting interference devices (SQUIDs), it is also a fundamental problem in condensed-matter physics. Recent technological progress in methods for both direct and indirect observation of vortices, e.g. scanning SQUID, terahertz imaging, and microwave excitation, has led to new insights into vortex physics, the dynamic behavior of vortices in junctions and related questions of noise. This book presents the current status of research activity and provides new information on the applications of SQUIDs, including magnetocardiography, immunoassays, and laser-SQUID microscopes, all of which are close to being commercially available.

  9. Photospheric magnetic vortex structures

    Directory of Open Access Journals (Sweden)

    S. Shelyag

    2011-05-01

    Full Text Available Using direct numerical magneto-hydrodynamic (MHD simulations, we demonstrate the evidence of two physically different types of vortex motions in the solar photosphere. Baroclinic motions of plasma in non-magnetic granules are the primary source of vorticity in granular regions of the solar photosphere, however, there is a significantly more efficient mechanism of vorticity production in strongly magnetised intergranular lanes. These swirly motions of plasma in intergranular magnetic field concentrations could be responsible for the generation of different types of MHD wave modes, for example, kink, sausage and torsional Alfvén waves. These waves could transport a relevant amount of energy from the lower solar atmosphere and contribute to coronal plasma heating.

  10. Experimental investigation of vortex rings impinging on inclined surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Couch, Lauren D. [Southern Methodist University, Department of Mechanical Engineering, Dallas, TX (United States); Georgia Institute of Technology, George W. Woodruff School of Mechanical Engineering, Atlanta, GA (United States); Krueger, Paul S. [Southern Methodist University, Department of Mechanical Engineering, Dallas, TX (United States)

    2011-10-15

    Vortex-ring interactions with oblique boundaries were studied experimentally to determine the effects of plate angle on the generation of secondary vorticity, the evolution of the primary vorticity and secondary vorticity as they interact near the boundary, and the associated energy dissipation. Vortex rings were generated using a mechanical piston-cylinder vortex ring generator at jet Reynolds numbers 2,000-4,000 and stroke length to piston diameter ratios (L/D) in the range 0.75-2.0. The plate angle relative to the initial axis of the vortex ring ranged from 3 to 60 . Flow analysis was performed using planar laser-induced fluorescence (PLIF), digital particle image velocimetry (DPIV), and defocusing digital particle tracking velocimetry (DDPTV). Results showed the generation of secondary vorticity at the plate and its subsequent ejection into the fluid. The trajectories of the centers of circulation showed a maximum ejection angle of the secondary vorticity occurring for an angle of incidence of 10 . At lower incidence angles (<20 ), the lower portion of the ring, which interacted with the plate first, played an important role in generation of the secondary vorticity and is a key reason for the maximum ejection angle for the secondary vorticity occurring at an incidence angle of 10 . Higher Reynolds number vortex rings resulted in more rapid destabilization of the flow. The three-dimensional DDPTV results showed an arc of secondary vorticity and secondary flow along the sides of the primary vortex ring as it collided with the boundary. Computation of the moments and products of kinetic energy and vorticity magnitude about the centroid of each vortex ring showed increasing asymmetry in the flow as the vortex interaction with the boundary evolved and more rapid dissipation of kinetic energy for higher incidence angles. (orig.)

  11. Vortex cores and vortex motion in superconductors with anisotropic Fermi surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Galvis, J.A. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Departamento de Ciencias Naturales, Facultad de ingeniería y Ciencias Básicas, Universidad Central, Bogotá (Colombia); National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States); Herrera, E.; Guillamón, I.; Vieira, S. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Altos Campos Magnéticos y Bajas Temperaturas, UAM, CSIC, Madrid (Spain); Suderow, H., E-mail: hermann.suderow@uam.es [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Altos Campos Magnéticos y Bajas Temperaturas, UAM, CSIC, Madrid (Spain)

    2017-02-15

    Highlights: • The observation of vortex cores is reviewed, with emphasis in new experiments. • Vortex cores are follow superconducting gap and Fermi surface shapes. • The vortex core shape influences vortex dynamics. - Abstract: Explaning static and dynamic properties of the vortex lattice in anisotropic superconductors requires a careful characterization of vortex cores. The vortex core contains Andreev bound states whose spatial extension depends on the anisotropy of the electronic band-structure and superconducting gap. This might have an impact on the anisotropy of the superconducting properties and on vortex dynamics. Here we briefly summarize basic concepts to understand anisotropic vortex cores and review vortex core imaging experiments. We further discuss moving vortex lattices and the influence of vortex core shape in vortex motion. We find vortex motion in highly tilted magnetic fields. We associate vortex motion to the vortex entry barrier and the screening currents at the surface. We find preferential vortex motion along the main axis of the vortex lattice. After travelling integers of the intervortex distance, we find that vortices move more slowly due to the washboard potential of the vortex lattice.

  12. Implementation of vortex wake control using SMA-actuated devices

    Science.gov (United States)

    Quackenbush, Todd R.; Bilanin, Alan J.; Batcho, P. F.; McKillip, Robert M., Jr.; Carpenter, Bernie F.

    1997-05-01

    Mitigation of the undesirable effects of trailing vortex wakes has been a long-standing priority for both reduction of submarine wake signature and alleviation of aircraft vortex wake hazard. A recent study established the feasibility of using relatively weak, secondary vortices with carefully selected unsteady amplitude and phasing to accelerate the breakup of the primary vortex system of a lifting surface, a technique denoted `vortex leveraging'. This paper will summarize progress on the development of SMA-actuated devices for implementing vortex leveraging for hydrodynamic applications. The methods being applied to the hydrodynamic design of these deformable Smart Vortex Leveraging Tabs (SVLTs) will be described, and the results of a preliminary assessment of SVLT performance in achieving wake breakup will be presented. Also, previous work on the design and testing of deformable control surfaces actuated via embedded SMA agonist wires will be reviewed and the design process being employed in the present applications will be discussed. Finally, the plans for near-term computational and experimental work to validate the use of SMA-driven devices for the wake mitigation task will be briefly outlined.

  13. Vortex dynamics and flow-induced vibrations arising from a vortex ring passing tangentially over a flexible plate

    Science.gov (United States)

    Pirnia, Alireza; Hu, JiaCheng; Peterson, Sean D.; Erath, Byron D.

    2017-10-01

    The extraction of energy from vortical structures advecting through an ambient environment is a topic of interest due to the potential to power miniature in situ sensors and monitors. This work investigates the vortex dynamics and flow-induced vibrations of a flexible plate arising from a vortex ring passing tangentially over it. Experimental measurements of the flow field and plate dynamics are performed in tandem with a coupled potential flow/Kirchhoff-Love plate model in order to (i) elucidate the physics of the vortex-plate interactions in the specified orientation and relate the energy exchange between the ring and the plate to the attendant vortex dynamics; (ii) validate the potential flow model and provide any needed corrections to account for the simplifying assumptions; and (iii) provide empirical data for estimating energy harvesting capabilities in the specified orientation. The plate loading arises as a result of an initial down-wash, followed quickly by a region of reduced pressure as the vortex core passes over the plate. The fundamental physics of the interaction is discussed, identifying three regimes. When the centerline of the vortex ring is positioned greater than approximately 2 vortex ring radii away from the plate it can be considered to be in the far-field, and the resulting vibrations are well predicted through potential flow, once the plate dynamics are corrected for edge effects arising from a finite plate width. As the offset distance of the vortex ring is decreased, diffusion of induced vorticity on the plate into the flow field significantly alters the fluid dynamics, pressure loading, and the resultant plate dynamics, and dramatically increases the strain energy in comparison with the potential flow model predictions. A first-order correction to the potential flow model is proposed to account for the finite plate width, while empirical correlations are presented for the plate strain energy in cases where ring/induced vorticity

  14. Investigation of vortex ring formation with account of generator piston motion

    Science.gov (United States)

    Khramtsov, I. V.; Palchikovskiy, VV; Siner, A. A.; Bersenev, Yu V.

    2017-06-01

    The formation and dynamics of such an elementary object of fluid dynamics as a vortex ring was investigated. Intense turbulent vortex rings created by a piston generator were considered. For qualitative determination of vortex ring properties, the law of motion for the generator’s piston was experimentally established. This law was used in the numerical simulation, which was performed for the axisymmetric problem formulation with the use of ANSYS Fluent software. The obtained results correspond to the self-similar law of vortex ring motion and experimental results.

  15. Local topological charge analysis of electromagnetic vortex beam based on empirical mode decomposition

    CERN Document Server

    Hui, Xiaonan; Zhang, Weite; Jin, Xiaofeng; Chi, Hao; Zhang, Xianmin

    2015-01-01

    The topological charge of an electromagnetic vortex beam depends on its wavefront helicity. For mixed vortex beams composed of several different coaxial vortices, the topological charge spectrum can be obtained by Fourier transform. However, the vortex beam is generally divergent and imperfect. It makes it significant to investigate the local topological charges, especially in radio frequency regime. Fourier transform based methods are restrained by the uncertainty principle and cannot achieve high angular resolution and mode resolution simultaneously. In this letter, an analysis method for local topological charges of vortex beams is presented based on the empirical mode decomposition (EMD). From EMD, the intrinsic mode functions (IMFs) can be obtained to construct the bases of the electromagnetic wave, and each local topological charge can be respectively defined. With this method the local value achieves both high resolution of azimuth angle and topological charge, meanwhile the amplitudes of each OAM mode...

  16. Transforming followers' value internalization and role self-efficacy: Dual processes promoting performance and peer norm-enforcement.

    Science.gov (United States)

    Hannah, Sean T; Schaubroeck, John M; Peng, Ann C

    2016-02-01

    We develop a model in which transformational leadership bolsters followers' internalization of core organizational values, which in turn influences their performance and willingness to report peers' transgressions. The model also specifies a distinct process wherein transformational leadership enhances follower performance by promoting followers' role self-efficacy. We tested the model on 2 large units (i.e., companies) of soldiers undergoing training and socialization. The study bracketed changes in soldiers' internalization of the organizational values and role self-efficacy over a 14-week period. The results support the widely held but empirically unestablished views that transformational leadership promotes change in value internalization and that this partially explains its influence on follower performance. Findings also indicate a distinct intervening process through which transformational leadership promotes performance by enhancing followers' beliefs in their own capabilities (i.e., self-efficacy). This research thus shows that 2 key processes both contribute to the understanding of how transformational leadership transforms followers and influences their behavior. (c) 2016 APA, all rights reserved).

  17. Particle-vortex symmetric liquid

    CERN Document Server

    Mulligan, Michael

    2016-01-01

    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 [Breznay et al., PNAS 113, 280 (2016)] to exhibit particle-vortex symmetric electrical response, and the metallic phase discovered earlier [Mason and Kapitulnik, Phys. Rev. Lett. 82, 5341 (1999)] 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 an (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 requir...

  18. Amplitude damping of vortex modes

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2010-09-01

    Full Text Available An interferometer, mimicking an amplitude damping channel for vortex modes, is presented. Experimentally the action of the channel is in good agreement with that predicted theoretically. Since we can characterize the action of the channel on orbital...

  19. Comparison between Corchorus olitorius and Corchorus capsularis at GUS histochemical assay performance for tissue culture independent transformation

    Directory of Open Access Journals (Sweden)

    REDUANUL BARI

    2015-08-01

    Full Text Available Tissue culture independent transformation technique in crops is relatively new and of popular interest due to its faster approach and efficiency. The prospect of this technique in the production of transgenic Jute plants with new genetic properties is promising. In the present study, two varieties of each of Corchorus olitorius (var. O-72 and var. OM-1 and C. capsularis (var. CVL-1 and var. BJC-83 were used to observe their transformation ability. Agrobacterium tumefaciens strain LBA4404 was used for transformation, which harbors a binary vector pBI121 containing selectable marker gene nptII, gus (β-glucuronidase reporter gene and a stress tolerance gene GLY-1. The young shoot tip of the seedlings (20-22 cm was infected with the bacterial culture. The young leaves were collected after 20-21 days of bacterial culture transformation and thereafter histochemical GUS assay was performed. In the putatively transformed regions of the plants, gus reporter gene was expressed showing blue color in the tissues. Non-transformed plants did not show any color. Among the varieties, the percentage of matured plants showing GUS activity was higher in C. olitorious var. O-72 (80.66% and OM-1 (73.33% compared to C. capsularis var. BJC-83 (32.50% and CVL-1 (40.00%. The result of the study provides an indication that efficiency of transformation by using tissue culture independent direct genetic transformation for the two species of Jute may differ significantly.

  20. Observation of the Dynamical Inversion of the Topological Charge of an Optical Vortex

    Science.gov (United States)

    Molina-Terriza, Gabriel; Recolons, Jaume; Torres, Juan P.; Torner, Lluis; Wright, Ewan M.

    2001-07-01

    We report what is believed to be the first detailed experimental observation of the dynamic inversion of the topological charge of an optical vortex under free-space propagation. The vortex self-transformation occurs through continuous deformation of the noncanonical strength of the corresponding screw wave front dislocation, and is mediated by the occurrence of an extremely sharp turn in a Berry vortex trajectory, which observed at a Freund critical foliation appears as an edge-line dislocation orthogonal to the propagation direction, at a crucial point of the light evolution.

  1. Observation of the Dynamical Inversion of the Topological Charge of an Optical Vortex

    Energy Technology Data Exchange (ETDEWEB)

    Molina-Terriza, Gabriel; Recolons, Jaume; Torres, Juan P.; Torner, Lluis; Wright, Ewan M.

    2001-07-09

    We report what is believed to be the first detailed experimental observation of the dynamic inversion of the topological charge of an optical vortex under free-space propagation. The vortex self-transformation occurs through continuous deformation of the noncanonical strength of the corresponding screw wave front dislocation, and is mediated by the occurrence of an extremely sharp turn in a Berry vortex trajectory, which observed at a Freund critical foliation appears as an edge-line dislocation orthogonal to the propagation direction, at a crucial point of the light evolution.

  2. Vortex Models for Data Assimilation

    OpenAIRE

    Darakananda, Darwin

    2017-01-01

    Inviscid vortex models have been used for decades to investigate unsteady aerodynamics. However, real-time use of these models has been hindered by the tradeoff between increasing a model's dynamical capability and reducing its dimensionality. In this work, we present two different solutions to this problem. First, we develop a hybrid model where vortex sheets represent shear layers that separate from the wing and point vortices represent the rolled-up cores of these shear layers and the o...

  3. The Impact Of Transformational Leadership On Job Satisfaction And Self-Perceived Performance Of Banking Employees: The Case Of Jordan

    OpenAIRE

    Raed Awamleh; Hani Al-Dmour Al-Dmour

    2011-01-01

    This study tested the transformational leadership theory among managers at functional level in Jordanian banks. It examined the effects of both transformational and transactional leadership styles of bank mangers/supervisors on employees satisfaction and self-perceived performance. Self-efficacy, self-esteem and leadership disposition (Romance of Leadership) of employees were hypothesized to act as moderators. Data was collected from employees working in Jordanian banks. A multiple regression...

  4. Transformational leadership, initiating structure, and substitutes for leadership: a longitudinal study of research and development project team performance.

    Science.gov (United States)

    Keller, Robert T

    2006-01-01

    Transformational leadership, initiating structure, and selected substitutes for leadership were studied as longitudinal predictors of performance in 118 research and development (R&D) project teams from 5 firms. As hypothesized, transformational leadership predicted 1-year-later technical quality, schedule performance, and cost performance and 5-year-later profitability and speed to market. Initiating structure predicted all the performance measures. The substitutes of subordinate ability and an intrinsically satisfying task each predicted technical quality and profitability, and ability predicted speed to market. Moderator effects for type of R&D work were hypothesized and found whereby transformational leadership was a stronger predictor of technical quality in research projects, whereas initiating structure was a stronger predictor of technical quality in development projects. Implications for leadership theory and research are discussed. (c) 2006 APA, all rights reserved.

  5. Instrumental concept and preliminary performances of SIFTI: static infrared fourier transform interferometer

    Science.gov (United States)

    Hébert, Philippe-Jean; Cansot, E.; Pierangelo, C.; Buil, C.; Bernard, F.; Loesel, J.; Trémas, T.; Perrin, L.; Courau, E.; Casteras, C.; Maussang, I.; Simeoni, D.

    2017-11-01

    The SIFTI (Static Infrared Fourier Transform Interferometer) instrument aims at supporting an important part in a mission for atmospheric pollution sounding from space, by providing high spectral resolution and high Signal to Noise Ratio spectra of the atmosphere. They will allow to resolve tropospheric profiles of ozone (03) and carbon monoxide (C0), especially down to the planetary boundary layer (PBL), an altitude region of very high interest, though poorly monitored to date, for air quality and pollution monitoring. The retrieved profile of ozone, resp. C0, will contain 5 to 7, resp. 2.5 to 4, independent pieces of information. The French space agency CNES (Centre National d'Etudes Spatiales) has proposed and is studying an instrument concept for SIFTI based on a static interferometer, where the needed optical path are generated by a pair of crossed staircase fixed mirrors (replacing the moving reflector of dynamic Fourier transform interferometers like IASI or MIPAS). With the SIFTI design, a very high spectral resolution ( 0.1 cm-1 apodised) is achieved in a very compact optical setup, allowing a large throughput, hence a high SNR. The measurements are performed in the 9.5 μm band for 03 and in the 4.6 μm band for C0. The science return of the sounder can be further increased if an "intelligent pointing" process is implemented. This consists in combining the TIR sounder with a companion TIR imager, providing information on the cloud coverage in the next observed scene. 0nboard, real-time analysis of the IR image is used to command the sounder staring mirror to cloud free areas, which will maximize the probability for probing down to the surface. After the first part of the phase A, the architecture of SIFTI was studied as a trade-off between performance and resource budget. We review the main architecture and functional choices, and their advantages. The preliminary instrument concept is then presented in its main aspects and in terms of main subsystem

  6. Transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons and the influence of the transformation strategies on the photocatalytic performance

    Directory of Open Access Journals (Sweden)

    Melita Rutar

    2015-03-01

    Full Text Available The influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon surfaces and their optical properties was investigated. The transformations were performed (i through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400–650 °C, (ii through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g/Ar(g flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti4+ to Ti3+. The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the

  7. A high-performance seizure detection algorithm based on Discrete Wavelet Transform (DWT) and EEG.

    Science.gov (United States)

    Chen, Duo; Wan, Suiren; Xiang, Jing; Bao, Forrest Sheng

    2017-01-01

    In the past decade, Discrete Wavelet Transform (DWT), a powerful time-frequency tool, has been widely used in computer-aided signal analysis of epileptic electroencephalography (EEG), such as the detection of seizures. One of the important hurdles in the applications of DWT is the settings of DWT, which are chosen empirically or arbitrarily in previous works. The objective of this study aimed to develop a framework for automatically searching the optimal DWT settings to improve accuracy and to reduce computational cost of seizure detection. To address this, we developed a method to decompose EEG data into 7 commonly used wavelet families, to the maximum theoretical level of each mother wavelet. Wavelets and decomposition levels providing the highest accuracy in each wavelet family were then searched in an exhaustive selection of frequency bands, which showed optimal accuracy and low computational cost. The selection of frequency bands and features removed approximately 40% of redundancies. The developed algorithm achieved promising performance on two well-tested EEG datasets (accuracy >90% for both datasets). The experimental results of the developed method have demonstrated that the settings of DWT affect its performance on seizure detection substantially. Compared with existing seizure detection methods based on wavelet, the new approach is more accurate and transferable among datasets.

  8. Wake Vortex Inverse Model User's Guide

    Science.gov (United States)

    Lai, David; Delisi, Donald

    2008-01-01

    NorthWest Research Associates (NWRA) has developed an inverse model for inverting landing aircraft vortex data. The data used for the inversion are the time evolution of the lateral transport position and vertical position of both the port and starboard vortices. The inverse model performs iterative forward model runs using various estimates of vortex parameters, vertical crosswind profiles, and vortex circulation as a function of wake age. Forward model predictions of lateral transport and altitude are then compared with the observed data. Differences between the data and model predictions guide the choice of vortex parameter values, crosswind profile and circulation evolution in the next iteration. Iterations are performed until a user-defined criterion is satisfied. Currently, the inverse model is set to stop when the improvement in the rms deviation between the data and model predictions is less than 1 percent for two consecutive iterations. The forward model used in this inverse model is a modified version of the Shear-APA model. A detailed description of this forward model, the inverse model, and its validation are presented in a different report (Lai, Mellman, Robins, and Delisi, 2007). This document is a User's Guide for the Wake Vortex Inverse Model. Section 2 presents an overview of the inverse model program. Execution of the inverse model is described in Section 3. When executing the inverse model, a user is requested to provide the name of an input file which contains the inverse model parameters, the various datasets, and directories needed for the inversion. A detailed description of the list of parameters in the inversion input file is presented in Section 4. A user has an option to save the inversion results of each lidar track in a mat-file (a condensed data file in Matlab format). These saved mat-files can be used for post-inversion analysis. A description of the contents of the saved files is given in Section 5. An example of an inversion input

  9. Regimes of flow past a vortex generator

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Okulov, V.L.; Naumov, I.V.

    2012-01-01

    particle image velocimetry (SPIV). Based on the obtained SPIV data, a map of the regimes of flow past the vortex generator has been constructed. One region with a developed stable multivortex system on this map reaches the vicinity of the optimum angle of attack of the vortex generator.......A complete parametric investigation of the development of multi-vortex regimes in a wake past simple vortex generator has been carried out. It is established that the vortex structure in the wake is much more complicated than a simple monopole tip vortex. The vortices were studied by stereoscopic...

  10. The influence of transformational leadership on workplace relationships and job performance

    National Research Council Canada - National Science Library

    Li, Chung-Kai; Hung, Chia-Hung

    2009-01-01

    .... Results indicate that all 4 dimensions of transformational leadership have positive effects on LMX, whereas only individualized consideration and inspirational motivation positively affect CWR...

  11. Exergoeconomic Performance Comparison and Optimization of Single-Stage Absorption Heat Transformers

    National Research Council Canada - National Science Library

    S Mohammad S Mahmoudi; Sina Salehi; Mortaza Yari; Marc A Rosen

    2017-01-01

    Three single-stage absorption heat transformer (SSHT) configurations are modeled, analyzed and compared from the viewpoints of thermodynamics and economics, using the Engineering Equation Solver (EES) software...

  12. Effect of vortex formation on sediment transport at dual pipe intakes

    Indian Academy of Sciences (India)

    Vortex formation and subsequent sediment transport into the intake due to sea water withdrawal is one of the problems in coastal engineering. The effect of vortex formation on rate of sediment transport at coastal dual pipe intakes was investigated using a scaled physical model. Experiments were performed on dual pipe ...

  13. Aeroelastic large eddy simulations using vortex methods: unfrozen turbulent and sheared inflow

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre; Papadakis, G.; Gaunaa, Mac

    2015-01-01

    Vortex particles methods are applied to the aeroelastic simulation of a wind turbine in sheared and turbulent inflow. The possibility to perform large-eddy simulations of turbulence with the effect of the shear vorticity is demonstrated for the first time in vortex methods simulations. Most vorte...

  14. The Impact of the Dimensions of Transformational Leadership on the Post-acquisition Performance of the Acquired Company

    Directory of Open Access Journals (Sweden)

    Sladjana Savovic

    2017-08-01

    Full Text Available Mergers and acquisitions (M&A are the important mechanisms through which companies can achieve growth, gain access to new markets and diversify their activities. Although companies engage themselves in M&As with optimism, empirical evidence shows that many M&A transactions are not successful. Therefore, research is often focused on the identification of the ways to improve post-acquisition performance. One of the key success factors of M&A is to provide adequate transformational leadership during the process of change, especially in the critical phase of the post-acquisition integration. A transformational leader should provide incentives and support to the employees in order for them to accept changes and focus on achieving challenging goals. This paper explores the impact of the different dimensions of transformational leadership on the post-acquisition performance based on the example of a company operating in the Republic of Serbia’s retail sector, which was the subject of a cross-border acquisition. In order to ensure the adequate representativeness of the sample, a questionnaire was distributed in all parts of the company throughout the Republic of Serbia. The results of this study show that all the dimensions of transformational leadership positively impact post-acquisition performance. The “individual consideration” dimension of transformational leadership has the strongest impact on post-acquisition performance, whereas the “intellectual simulation” dimension has the weakest.

  15. EFFECT OF TRANSACTIONAL AND TRANSFORMATIONAL LEADERSHIP STYLE, MOTIVATION AND COMPETENCE TO PERFORMANCE OF EMPLOYEES PT. SANJAYATAMA LESTARI

    Directory of Open Access Journals (Sweden)

    Jublina Oktora

    2016-09-01

    Full Text Available In this study, the objective is to conduct a systematic examination Effect of Transactional and Transformational Leadership Style, Motivation and Competence to Employee Performance PT. Sanjayatama Lestari. The samples used were employees of PT. Sanjayatama Lestari the number of respondents as many as 95 people. The analysis used is multiple linear regression. This study examined five variables: Transactional Leadership Style (X1, Transformational Leadership Style (X2, motivation (X3 and Competence (X4 as the independent variable and the performance (Y as the dependent variable. Partial test shows that the transactional leadership style influenced by 3.876 (positive and significant on the performance. Transformational leadership style also influenced significantly by 3.128. Furthermore, the motivation also has a significant influence amounted to 4.210 and the latter is the competence of significant influence amounted to 6.283.

  16. When visuo-motor incongruence aids motor performance : the effect of perceiving motion structures during transformed visual feedback on bimanual coordination

    NARCIS (Netherlands)

    Bogaerts, H; Buekers, MJ; Zaal, FT; Swinnen, SP

    2003-01-01

    Two experiments are reported in which bimanual coordination tasks were performed under correct and transformed visual feedback conditions. Participants were to generate cyclical line-drawing patterns, with varying degrees of coordinative stability, while perceiving correct or transformed visual

  17. Experimental study on a simple Ranque Hilsch vortex tube

    Science.gov (United States)

    Gao, C. M.; Bosschaart, K. J.; Zeegers, J. C. H.; de Waele, A. T. A. M.

    2005-03-01

    The Ranque-Hilsch vortex tube is a device by which cold gas can be generated using compressed gas. To understand the cooling mechanism of this device, it is necessary to know the pressure, temperature, and velocity distributions inside the tube. In order to investigate this, a simple vortex tube is built and nitrogen is used as its working fluid. A special Pitot tube is used for the measurement of the pressure and velocity. This Pitot tube consists of a capillary which has only one hole in the cylinder wall. With this Pitot tube, the pressure and velocity fields inside the tube were measured. In the same way, the temperature field was measured with a thermocouple. The results of three different entrance conditions are compared here. With the measurements results, the analysis based on the two thermodynamic laws has been made. It is found that rounding off the entrance has influence on the performance of the vortex tube. The secondary circulation gas flow inside the vortex tube can be enhanced and enlarged, the performance of the Ranque-Hilsch vortex tube improved.

  18. Transformational leadership sub-dimensions and their link to leaders' personality and performance

    NARCIS (Netherlands)

    Deinert, A.; Homan, A.C.; Boer, D.; Voelpel, S.C.; Gutermann, D.

    2015-01-01

    The multi-dimensionality of the transformational leadership construct has been under debate in the last decades. To shed more light on this issue, we conducted a meta-analysis (k = 58 studies), examining the transformational leadership sub-dimensions and their links to leader personality and

  19. Alleviation of fuselage form drag using vortex flows: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Wortman, A.

    1987-09-15

    The concept of using vortex generators to reduce the fuselage form drag of transport aircraft combines the outflow from the plane of symmetry which is induced by the rotational component of the vortex flow with the energization of the boundary layer to reduce the momentum thickness and to delay or eliminate flow separation. This idea was first advanced by the author in 1981. Under a DOE grant, the concept was validated in wind tunnel tests of approximately 1:17 scale models of fuselages of Boeing 747 and Lockheed C-5 aircraft. The search for the minimum drag involved three vortex generator configurations with three sizes of each in six locations clustered in the aft regions of the fuselages at the beginning of the tail upsweep. The local Reynolds number, which is referred to the length of boundary layer run from the nose, was approximately 10{sup 7} so that a fully developed turbulent boundary layer was present. Vortex generator planforms ranged from swept tapered, through swept straight, to swept reverse tapered wings whose semi-spans ranged from 50% to 125% of the local boundary layer thickness. Pitch angles of the vortex generators were varied by inboard actuators under the control of an external proportional digital radio controller. It was found that certain combinations of vortex generator parameters increased drag. However, with certain configurations, locations, and pitch angles of vortex generators, the highest drag reductions were 3% for the 747 and about 6% for the C-5, thus confirming the arguments that effectiveness increases with the rate of upsweep of the tail. Greatest gains in performance are therefore expected on aft loading military transports. 10 refs., 11 figs., 1 tab.

  20. Relative equilibria of vortex arrays

    Science.gov (United States)

    Stremler, Mark

    2002-11-01

    Experiments with vibrating and oscillating cylinders have demonstrated that exotic vortex patterns can emerge in laminar wake flows. These wakes arise when more than two vortices are generated per shedding cycle. The Karman vortex street has proven to be a useful model for investigating the standard wake flow with two vortices per period; this utility suggests that it will be instructive to investigate other singly-periodic point vortex configurations that move without change of shape or size. The existence and structure of such relative equilibria of vortex arrays will be presented. Motivation for investigating these equilibria, all of which appear to be unstable, comes from the observation that the dynamics of a system slows down in the vicinity of unstable equilibria. Thus, states close to these equilibria can remain for a relatively long time, as illustrated by recent experiments in strongly magnetized electron plasma. The investigation of the relative equilibria of vortex arrays can thus provide a `road-map' for states that may be observable in laminar wake experiments.

  1. Point vortex modelling of the wake dynamics behind asymmetric vortex generator arrays

    NARCIS (Netherlands)

    Baldacchino, D.; Simao Ferreira, C.; Ragni, D.; van Bussel, G.J.W.

    2016-01-01

    In this work, we present a simple inviscid point vortex model to study the dynamics of asymmetric vortex rows, as might appear behind misaligned vortex generator vanes. Starting from the existing solution of the in_nite vortex cascade, a numerical model of four base-vortices is chosen to represent

  2. Intelligent Models Performance Improvement Based on Wavelet Algorithm and Logarithmic Transformations in Suspended Sediment Estimation

    Directory of Open Access Journals (Sweden)

    R. Hajiabadi

    2016-10-01

    Full Text Available Introduction One reason for the complexity of hydrological phenomena prediction, especially time series is existence of features such as trend, noise and high-frequency oscillations. These complex features, especially noise, can be detected or removed by preprocessing. Appropriate preprocessing causes estimation of these phenomena become easier. Preprocessing in the data driven models such as artificial neural network, gene expression programming, support vector machine, is more effective because the quality of data in these models is important. Present study, by considering diagnosing and data transformation as two different preprocessing, tries to improve the results of intelligent models. In this study two different intelligent models, Artificial Neural Network and Gene Expression Programming, are applied to estimation of daily suspended sediment load. Wavelet transforms and logarithmic transformation is used for diagnosing and data transformation, respectively. Finally, the impacts of preprocessing on the results of intelligent models are evaluated. Materials and Methods In this study, Gene Expression Programming and Artificial Neural Network are used as intelligent models for suspended sediment load estimation, then the impacts of diagnosing and logarithmic transformations approaches as data preprocessor are evaluated and compared to the result improvement. Two different logarithmic transforms are considered in this research, LN and LOG. Wavelet transformation is used to time series denoising. In order to denoising by wavelet transforms, first, time series can be decomposed at one level (Approximation part and detail part and second, high-frequency part (detail will be removed as noise. According to the ability of gene expression programming and artificial neural network to analysis nonlinear systems; daily values of suspended sediment load of the Skunk River in USA, during a 5-year period, are investigated and then estimated.4 years of

  3. Cylindrical sound wave generated by shock-vortex interaction

    Science.gov (United States)

    Ribner, H. S.

    1985-01-01

    The passage of a columnar vortex broadside through a shock is investigated. This has been suggested as a crude, but deterministic, model of the generation of 'shock noise' by the turbulence in supersonic jets. The vortex is decomposed by Fourier transform into plane sinusoidal shear waves disposed with radial symmetry. The plane sound waves produced by each shear wave/shock interaction are recombined in the Fourier integral. The waves possess an envelope that is essentially a growing cylindrical sound wave centered at the transmitted vortex. The pressure jump across the nominal radius R = ct attenuates with time as 1/(square root of R) and varies around the arc in an antisymmetric fashion resembling a quadrupole field. Very good agreement, except near the shock, is found with the antisymmetric component of reported interferometric measurements in a shock tube. Beyond the front r approximately equals R is a precursor of opposite sign, that decays like 1/R, generated by the 1/r potential flow around the vortex core. The present work is essentially an extension and update of an early approximate study at M = 1.25. It covers the range (R/core radius) = 10, 100, 1000, and 10,000 for M = 1.25 and (in part) for M = 1.29 and, for fixed (R/core radius) = 1000, the range M = 1.01 to infinity.

  4. Study of propagation of vortex beams in aerosol optical medium.

    Science.gov (United States)

    Porfirev, Alexey P; Kirilenko, Mikhail S; Khonina, Svetlana N; Skidanov, Roman V; Soifer, Victor A

    2017-04-10

    A theoretical and experimental study of the propagation of vortex laser beams in a random aerosol medium is presented. The theoretical study is based on the extended Huygens-Fresnel principle with the generation of a random field, using the fast Fourier transform. The simulation shows that the stability of vortex beams to fluctuations of an optical medium falls with rising order of optical vortices. Moreover, a coherence length (radius) of the random medium is of great importance. The coherence radius extension affects adversely the conservation of a beam structure in the random medium. During further free-space propagation, increasing coherence enables reduction of the negative effects of fluctuations for beams with high-value topological charges. Experimental studies in the random aerosol medium have shown that at small distances vortex beams mostly demonstrate lower stability than a Gaussian beam. However, at considerable distances, vortex beams start to demonstrate greater stability that may be explained by their capacity to be regenerated after they passed obstacles.

  5. MULTIMODAL IMAGING IN VORTEX VEIN VARICES.

    Science.gov (United States)

    Veronese, Chiara; Staurenghi, Giovanni; Pellegrini, Marco; Maiolo, Chiara; Primavera, Laura; Morara, Mariachiara; Armstrong, Grayson W; Ciardella, Antonio P

    2017-03-22

    The aim of this study is to describe the clinical presentation of vortex vein varices with multimodal imaging. The authors carried out a retrospective case series of eight patients (7 female, 1 male) with an average age of 60.2 years (min 8, max 84, median 68.5) presenting with vortex vein varices. All patients were evaluated at the Sant'Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy and at Luigi Sacco Hospital, University of Milan, Milan, Italy. Patients underwent complete ophthalmologic examinations, including best corrected visual acuity, intraocular pressure, anterior segment, and fundus examination. Imaging studies, including fundus color photography, near-infrared reflectance imaging, fundus autofluorescence, fluorescein angiography, indocyanine green angiography, and spectral-domain enhanced depth imaging optical coherence tomography were also performed. Ultra-widefield fluorescein angiography and ultra-widefield indocyanine angiography using the Heidelberg Retina Angiograph and the Staurenghi 230 SLO Retina Lens were used to demonstrate the disappearance of all retinal lesions when pressure was applied to the globe. All eight cases initially presented to the emergency room. One patient presented secondary to trauma, two patients presented for suspected hemangioma, whereas the other five were referred to the authors' hospitals for suspected retinal lesions. On examination, retinal abnormalities were identified in all 8 patients, with 7 (87.5%) oculus dexter and 1 (12.5%) oculus sinister, and with 1 (12.5%) inferotemporally, 3 (37.5%) superonasally, 3 (37.5%) inferonasally, and 1 (12.5%) inferiorly. Fundus color photography showed an elevated lesion in seven patients and a nonelevated red lesion in one patient. In all patients, near-infrared reflectance imaging showed a hyporeflective lesion in the periphery of the retina. Fundus autofluorescence identified round hypofluorescent rings surrounding weakly hyperfluorescent lesions in all

  6. Magnetic Vortex Based Transistor Operations

    Science.gov (United States)

    Kumar, D.; Barman, S.; Barman, A.

    2014-02-01

    Transistors constitute the backbone of modern day electronics. Since their advent, researchers have been seeking ways to make smaller and more efficient transistors. Here, we demonstrate a sustained amplification of magnetic vortex core gyration in coupled two and three vortices by controlling their relative core polarities. This amplification is mediated by a cascade of antivortex solitons travelling through the dynamic stray field. We further demonstrated that the amplification can be controlled by switching the polarity of the middle vortex in a three vortex sequence and the gain can be controlled by the input signal amplitude. An attempt to show fan-out operation yielded gain for one of the symmetrically placed branches which can be reversed by switching the core polarity of all the vortices in the network. The above observations promote the magnetic vortices as suitable candidates to work as stable bipolar junction transistors (BJT).

  7. Magnetic Vortex Based Transistor Operations

    Science.gov (United States)

    Kumar, D.; Barman, S.; Barman, A.

    2014-01-01

    Transistors constitute the backbone of modern day electronics. Since their advent, researchers have been seeking ways to make smaller and more efficient transistors. Here, we demonstrate a sustained amplification of magnetic vortex core gyration in coupled two and three vortices by controlling their relative core polarities. This amplification is mediated by a cascade of antivortex solitons travelling through the dynamic stray field. We further demonstrated that the amplification can be controlled by switching the polarity of the middle vortex in a three vortex sequence and the gain can be controlled by the input signal amplitude. An attempt to show fan–out operation yielded gain for one of the symmetrically placed branches which can be reversed by switching the core polarity of all the vortices in the network. The above observations promote the magnetic vortices as suitable candidates to work as stable bipolar junction transistors (BJT). PMID:24531235

  8. Altered regional homogeneity with short-term simulated microgravity and its relationship with changed performance in mental transformation.

    Directory of Open Access Journals (Sweden)

    Yang Liao

    Full Text Available In order to further the insight into the explanation of changed performance in mental transformation under microgravity, we discuss the change of performance in mental transformation and its relationship with altered regional homogeneity (ReHo in resting-state brain by using simulated weightlessness model. Twelve male subjects with age between 24 and 31 received resting-state fMRI scan and mental transformation test both in normal condition and immediately after 72 hours -6° head down tilt (HDT. A paired sample t-test was used to test the difference of behavior performance and brain activity between these two conditions. Compare with normal condition, subjects showed a changed performance in mental transformation with short term simulated microgravity and appeared to be falling. Meanwhile, decreased ReHo were found in right inferior frontal gyrus (IFG and left inferior parietal lobule (IPL after 72 hours -6° HDT, while increased ReHo were found in bilateral medial frontal gyrus (MFG and left superior frontal gyrus (SFG (P<0.05, corrected. Particularly, there was a significant correlation between ReHo values in left IPL and velocity index of mental transformation. Our findings indicate that gravity change may disrupt the function of right IFG and left IPL in the resting-state, among of which functional change in left IPL may contribute to changed abilities of mental transformation. In addition, the enhanced activity of the bilateral MFG and decreased activity of right IFG found in the current study maybe reflect a complementation effect on inhibitory control process.

  9. The intraventricular filling vortex under heightened aortic blood pressure

    Science.gov (United States)

    Nelsen, Nicholas; Gaddam, Manikantam; Santhanakrishnan, Arvind

    2017-11-01

    Hypertension, or high aortic blood pressure, can induce structural changes in the left ventricle (LV) such as concentric hypertrophy. Previous studies have identified that the intraventricular filling vortex serves as an effective means of blood transport during diastolic filling. However, a fundamental understanding of how hypertension affects this vortex is unavailable. This knowledge can be useful for improving diagnosis and treatment of related heart disease conditions, including hypertensive heart failure. In this experimental study, we hypothesized that the circulation of the filling vortex would diminish with increased aortic pressure. Using a LV physical model within a left heart simulator, we performed hemodynamic measurements to acquire pressure and volumetric inflow profiles and 2D particle image velocimetry to visualize the intraventricular flow fields. Peak aortic pressures of 120 mm Hg, 140 mm Hg, and 160 mm Hg were each tested at heart rates of 70, 100, and 110 beats per minute, under: 1) reduced ejection fraction (EF), and 2) constant EF. Our results indicate that peak vortex circulation is reduced under elevated aortic pressures. Hemodynamics and characteristics of the intraventricular filling vortex in all examined experimental cases will be presented.

  10. Network-theoretic approach to model vortex interactions

    Science.gov (United States)

    Nair, Aditya; Taira, Kunihiko

    2014-11-01

    We present a network-theoretic approach to describe a system of point vortices in two-dimensional flow. By considering the point vortices as nodes, a complete graph is constructed with edges connecting each vortex to every other vortex. The interactions between the vortices are captured by the graph edge weights. We employ sparsification techniques on these graph representations based on spectral theory to construct sparsified models of the overall vortical interactions. The edge weights are redistributed through spectral sparsification of the graph such that the sum of the interactions associated with each vortex is maintained constant. In addition, sparse configurations maintain similar spectral properties as the original setup. Through the reduction in the number of interactions, key vortex interactions can be highlighted. Identification of vortex structures based on graph sparsification is demonstrated with an example of clusters of point vortices. We also evaluate the computational performance of sparsification for large collection of point vortices. Work supported by US Army Research Office (W911NF-14-1-0386) and US Air Force Office of Scientific Research (YIP: FA9550-13-1-0183).

  11. Experimental study of the dynmamics of a stretched vortex

    Science.gov (United States)

    Petitjeans, Philippe; Bottausci, Frederic; Maurel, Agnes

    2001-11-01

    Numerical simulations of turbulent flows as well as real experiments indicates that a large part of vorticity in generic velocity fields is concentrated in localized regions in the form of filaments. The creation of such structures can be accounted for by the action of stretching on vorticity field, e.g. secondary instability mechanism in stretched vortex sheets. An experiment is performed in order to create a single stretched vortex that is supposed to have the same dynamics than these filaments of vorticity. The initial vorticity comes from a laminar boundary layer flow in a low velocity water channel, and the stretching is produced by succion through two holes located on the lateral walls of the channel. When the stretching is strong enough, a vortex is created that remains at its location attached to the succion holes. Recent results on the charateristics of this vortex will be presented. Instabilities of such a structure may produce the explosion of the vortex as a turbulent spot. This behaviour will be described and characterized.

  12. The Relationship of Cultural Intelligence, Transformational Leadership Style, and Team Performance in Culturally Diverse Student Leaders in Christian Higher Education

    Science.gov (United States)

    Menna, Tamene Yoseph

    2017-01-01

    The purpose of this study was to examine the relationship between cultural intelligence, transformational leadership, and team performance in one private Christian higher education institution in Southern California. The study further conducted initial exploration of how student leaders' Christian worldview (humility) influences their cultural…

  13. The Stand for Determination of Service Performance in Load of a Welding Transformer Using the LabVIEW Environment

    Directory of Open Access Journals (Sweden)

    Lenuţa Suciu

    2010-10-01

    Full Text Available This paper presents the way of performance’s characteristics determi-nation in load of welding transformers` performance parameters using the data acquisition systems through virtual tools. Nowadays observing the parameters of welding service and of welding instruments` charac-teristics means an important step regarding the quality of weld throat.

  14. The Role of Transformational Leadership, Organizational Culture and Organizational Learning in Improving the Performance of Iranian Agricultural Faculties

    Science.gov (United States)

    Abbasi, Enayat; Zamani-Miandashti, Naser

    2013-01-01

    This empirical research was conducted to investigate the role of transformational leadership, organizational culture and organizational learning in improving the performance of Iranian agricultural faculties and leading them to become learning organizations. The research population consisted of all faculty members of public agricultural faculties…

  15. Isokinetic muscle performance and salivary immune-endocrine responses in handball players by Fourier transform infrared spectroscopy

    Directory of Open Access Journals (Sweden)

    P.C. Caetano Júnior

    2017-09-01

    Conclusions: The handball players had good muscle performance of the lower limbs in the isokinetic evaluation. The Fourier transform infrared spectroscopy analysis identified the main absorption bands of cortisol and salivary cortisol and immunoglobulin A, as well as playing positions that demand higher stress levels, through changes of bands related to salivary cortisol.

  16. Vortex ice in nanostructured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, Andras J [Los Alamos National Laboratory

    2008-01-01

    We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

  17. Transition and mixing in axisymmetric jets and vortex rings

    Science.gov (United States)

    Allen, G. A., Jr.; Cantwell, B. J.

    1986-10-01

    A class of impulsively started, axisymmetric, laminar jets produced by a time dependent joint source of momentum are considered. These jets are different flows, each initially at rest in an unbounded fluid. The study is conducted at three levels of detail. First, a generalized set of analytic creeping flow solutions are derived with a method of flow classification. Second, from this set, three specific creeping flow solutions are studied in detail: the vortex ring, the round jet, and the ramp jet. This study involves derivation of vorticity, stream function, entrainment diagrams, and evolution of time lines through computer animation. From entrainment diagrams, critical points are derived and analyzed. The flow geometry is dictated by the properties and location of critical points which undergo bifurcation and topological transformation (a form of transition) with changing Reynolds number. Transition Reynolds numbers were calculated. A state space trajectory was derived describing the topological behavior of these critical points. This state space derivation yielded three states of motion which are universal for all axisymmetric jets. Third, the axisymmetric round jet is solved numerically using the unsteady laminar Navier Stokes equations. These equations were shown to be self similar for the round jet. Numerical calculations were performed up to a Reynolds number of 30 for a 60x60 point mesh. Animations generated from numerical solution showed each of the three states of motion for the round jet, including the Re = 30 case.

  18. Experimental analysis of Taylor vortex solid-liquid separation

    OpenAIRE

    河合, 秀樹; 岸川, 真吾; 木倉, 宏成; 有冨, 正憲; 高橋, 洋志

    2004-01-01

    It is known that rotating membrane filtration using a Taylor-Couette vortex flow (TCVF) system has an effect which reduces build-up of a cake layer on a surface of membrane filter. Although it is expected that the effect leads, for example to development of a new hemodialysis filter, fluid dynamic analysis is seldom performed. Here, TCVF is visualized by laser sheet device to study the fundamental vortex structure and then, by replacing the rigid inner cylinder with the filter, the particle-l...

  19. Vortex configuration and vortex-vortex interaction in nano-structured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Masaru, E-mail: kato@ms.osakafu-u.ac.jp [Department of Mathematical Sciences, Osaka Prefecture University, 1-1, Gakuencho, Naka-ku, Sakai, Osaka 599-8531 (Japan); CREST, JST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Niwa, Yuhei [Department of Mathematical Sciences, Osaka Prefecture University, 1-1, Gakuencho, Naka-ku, Sakai, Osaka 599-8531 (Japan); CREST, JST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Suematsu, Hisataka [Nanoscience and Nanotechnology Research Center, Osaka Prefecture University, 1-2, Gakuencho, Naka-ku, Sakai, Osaka 599-8570 (Japan); CREST, JST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Ishida, Takekazu [Department of Physics and Electronics, Osaka Prefecture University, 1-1, Gakuencho, Naka-ku, Sakai, Osaka 599-8531 (Japan); CREST, JST, 5 Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan)

    2012-09-15

    We study the vortex structures and quasi-particle structures in nano-structured superconductors. We used the Bogoliubov-de Gennes equation and the finite element method and obtained stable magnetic flux structures and the quasi-particle states. We found the vortex configurations are affected by the interference of the quasi-particle bound states around the vortices. In order to clarify the interference between the quasi-particle wave-functions around two vortices we have developed a numerical method using the elliptic coordinates and the Mathieu functions. We apply this method to two singly quantized vortex state in a conventional s-wave superconductor and a pair of half-quantum vortices in a chiral p-wave superconductor.

  20. Three-dimensional vortex-bright solitons in a spin-orbit-coupled spin-1 condensate

    Science.gov (United States)

    Gautam, Sandeep; Adhikari, S. K.

    2018-01-01

    We demonstrate stable and metastable vortex-bright solitons in a three-dimensional spin-orbit-coupled three-component hyperfine spin-1 Bose-Einstein condensate (BEC) using numerical solution and variational approximation of a mean-field model. The spin-orbit coupling provides attraction to form vortex-bright solitons in both attractive and repulsive spinor BECs. The ground state of these vortex-bright solitons is axially symmetric for weak polar interaction. For a sufficiently strong ferromagnetic interaction, we observe the emergence of a fully asymmetric vortex-bright soliton as the ground state. We also numerically investigate moving solitons. The present mean-field model is not Galilean invariant, and we use a Galilean-transformed mean-field model for generating the moving solitons.

  1. Generating, Separating and Polarizing Terahertz Vortex Beams via Liquid Crystals with Gradient-Rotation Directors

    Directory of Open Access Journals (Sweden)

    Shi-Jun Ge

    2017-10-01

    Full Text Available Liquid crystal (LC is a promising candidate for terahertz (THz devices. Recently, LC has been introduced to generate THz vortex beams. However, the efficiency is intensely dependent on the incident wavelength, and the transformed THz vortex beam is usually mixed with the residual component. Thus, a separating process is indispensable. Here, we introduce a gradient blazed phase, and propose a THz LC forked polarization grating that can simultaneously generate and separate pure THz vortices with opposite circular polarization. The specific LC gradient-rotation directors are implemented by a photoalignment technique. The generated THz vortex beams are characterized with a THz imaging system, verifying features of polarization controllability. This work may pave a practical road towards generating, separating and polarizing THz vortex beams, and may prompt applications in THz communications, sensing and imaging.

  2. Memory formation and evolution of the vortex configuration associated with random organization

    Science.gov (United States)

    Dobroka, M.; Kawamura, Y.; Ienaga, K.; Kaneko, S.; Okuma, S.

    2017-05-01

    We study the general phenomenon of random organization using a vortex system. When a periodic shear with a small shear amplitude d inp is applied to many-particle (vortex) assemblies with a random distribution, the particles (vortices) gradually self-organize to avoid future collisions and transform into an organized configuration. This is detected from the time-evolution of the voltage V(t) (average velocity) that increases towards a steady-state value. From the subsequent readout measurements of V(t) using various shear amplitudes, we find that the information of the input shear amplitude d inp is memorized in the configuration of the vortex distributions in the transient as well as the steady state, and that it is readable. We also find that the transient vortex configuration formed during random organization is not microscopically homogeneous but consists of disordered and organized regions.

  3. Universal statistics of vortex lines.

    Science.gov (United States)

    Nahum, Adam; Chalker, J T

    2012-03-01

    We study the vortex lines that are a feature of many random or disordered three-dimensional systems. These show universal statistical properties on long length scales, and geometrical phase transitions analogous to percolation transitions but in distinct universality classes. The field theories for these problems have not previously been identified, so that while many numerical studies have been performed, a framework for interpreting the results has been lacking. We provide such a framework with mappings to simple supersymmetric models. Our main focus is on vortices in short-range-correlated complex fields, which show a geometrical phase transition that we argue is described by the CP(k|k) model (essentially the CP(n-1) model in the replica limit n→1). This can be seen by mapping a lattice version of the problem to a lattice gauge theory. A related field theory with a noncompact gauge field, the 'NCCP(k|k) model', is a supersymmetric extension of the standard dual theory for the XY transition, and we show that XY duality gives another way to understand the appearance of field theories of this type. The supersymmetric descriptions yield results relevant, for example, to vortices in the XY model and in superfluids, to optical vortices, and to certain models of cosmic strings. A distinct but related field theory, the RP(2l|2l) model (or the RP(n-1) model in the limit n→1) describes the unoriented vortices that occur, for instance, in nematic liquid crystals. Finally, we show that in two dimensions, a lattice gauge theory analogous to that discussed in three dimensions gives a simple way to see the known relation between two-dimensional percolation and the CP(k|k) σ model with a θ term.

  4. Experiment of Waves on a Vortex filament

    OpenAIRE

    渡辺, 慎介; 舟久保, 悠子; Shinsuke, WATANABE; Yuko, FUNAKUBO; 横浜国大工; Department of Physics Yokohama National University; Department of Energy Engineering Faculty of Engineering, Yokohama National University

    2000-01-01

    Experiment of waves on a vortex filament is reported. A vertical vortex filament is generated by an axial flow of water in a cylindrical tank with a small hole in the center of the bottom. The motion of a vortex filament is controlled by a solid disk inserted from the top of water tank. When the disk is flapped sinusoidally around a horizontal axis, a vortex filament tends to contact perpendicularly with a disk, and begins to move on the disk. The motion brings about perturbations on a vortex...

  5. 3D micro-optical elements for generation of tightly focused vortex beams

    Directory of Open Access Journals (Sweden)

    Balčytis Armandas

    2015-01-01

    Full Text Available Orbital angular momentum carrying light beams are usedfor optical trapping and manipulation. This emerging trend provides new challenges involving device miniaturization for improved performance and enhanced functionality at the microscale. Here we discus a new fabrication method based on combining the additive 3D structuring capability laser photopolymerization and the substractive sub-wavelength resolution patterning of focused ion beam lithography to produce micro-optical elements capable of compound functionality. As a case in point of this approach binary spiral zone pattern based high numerical aperture micro-lenses capable of generating topological charge carrying tightly focused vortex beams in a single wavefront transformation step are presented. The devices were modelled using finite-difference time-domain simulations, and the theoretical predictions were verified by optically characterizing the propagation properties of light transmitted through the fabricated structures. The resulting devices had focal lengths close to the predicted values of f = 18 µm and f = 13 µm as well as topological charge ℓ dependent vortex focal spot sizes of ~ 1:3 µm and ~ 2:0 µm for ℓ = 1 and ℓ = 2 respectively.

  6. Visualization of flow separation and control by vortex generators on an single flap in landing configuration

    Directory of Open Access Journals (Sweden)

    Matějka Milan

    2012-04-01

    Full Text Available This paper focuses on a suppression of the flow separation, which occurs on a deflected flap, by means of vortex generators (VG's. An airfoil NACA 63A421 with a simple flap and vane-type vortex generators were used. The investigation was carried out by using experimental and numerical methods. The data from the numerical simulation of the flapped airfoil without VG's control were used for the vortex generator design. Two sizes, two different shapes and various spacing of the vortex generators were tested. The flow past the airfoil was visualized through three methods, namely tuft filaments technique, oil and thermo camera visualization. The experiments were performed in closed circuit wind tunnels with closed and open test sections. The lift curves for both cases without and with vortex generators were acquired for a lift coefficient improvement determination. The improvement was achieved for several cases by means all of the applied methods.

  7. Effects Of Ignition on Premixed Vortex Rings: A Simultaneous PLIF and PIV Investigation

    Science.gov (United States)

    Meyer, T. R.; Gord, J. R.; Katta, V. R.; Gogineni, S. P.

    2001-11-01

    Preliminary studies of reacting, premixed vortex rings have shown that flame propagation is highly sensitive to ignition timing, equivalence ratio, and vortex strength. A variety of divergent phenomena have been observed, such as interior/exterior flame propagation, vortex-induced flame bridging across the jet column, and the formation of unburned pockets. In the current work, planar laser-induced fluorescence (PLIF) of acetone and OH is performed to study the non-reacting and reacting regions, respectively, and particle image velocimetry (PIV) is used to study the effects of reaction on the flow field. The flow field consists of well-characterized vortex rings of premixed methane and air generated at the exit of an axisymmetric nozzle using a solenoid-driven piston. Ignition is initiated at various phases of vortex development and propagation. Results are compared with corresponding numerical simulations from a time-dependent computational fluid dynamics code with chemistry.

  8. Simulations of wind turbine rotor with vortex generators

    DEFF Research Database (Denmark)

    Zahle, Frederik; Sørensen, Niels N.

    2016-01-01

    This work presents simulations of the DTU 10MW wind turbine rotor equipped with vortex generators (VGs) on the inner part of the blades. The objective is to study the influence of different VG configurations on rotor performance and in particular to investigate the radial dependence of VGs, i.e...

  9. Thermal inhomogeneities in vortex tubes

    Science.gov (United States)

    Lemesh, N. I.; Senchuk, L. A.

    An experimental study of the effect of the temperature of the inlet gas on the temperature difference between the hot and cold streams discharged from a Ranque-Hilsch vortex tube is described. The experimental results are presented in graphical form. It is that the temperature difference increases with the temperature of the entering gas.

  10. Vortex dynamics in inhomogeneous plasmas

    DEFF Research Database (Denmark)

    Naulin, V.; Juul Rasmussen, J.

    1999-01-01

    The dynamics of vortical structures in magnetized plasmas with nonuniform density is investigated numerically. In particular the dynamics of monopolar vortices is considered and the results are discussed in terms of the conservation of potential vorticity. It is found that individual vortex...

  11. 150 Years of vortex dynamics

    DEFF Research Database (Denmark)

    Aref, Hassan

    2010-01-01

    An IUTAM symposium with the title of this paper was held on October 12-16, 2008, in Lyngby and Copenhagen, Denmark, to mark the sesquicentennial of publication of Helmholtz's seminal paper on vortex dynamics. This volume contains the proceedings of the Symposium. The present paper provides...

  12. Anatomy of a Bathtub Vortex

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; Bohr, Tomas; Stenum, Bjarne

    2003-01-01

    We present experiments and theory for the "bathtub vortex," which forms when a fluid drains out of a rotating cylindrical container through a small drain hole. The fast down-flow is found to be confined to a narrow and rapidly rotating "drainpipe" from the free surface down to the drain hole. Sur...

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

    Science.gov (United States)

    Medina, Albert; Jones, Anya R.

    2016-08-01

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

  14. Fast vortex oscillations in a ferrimagnetic disk near the angular momentum compensation point

    Science.gov (United States)

    Kim, Se Kwon; Tserkovnyak, Yaroslav

    2017-07-01

    We theoretically study the oscillatory dynamics of a vortex core in a ferrimagnetic disk near its angular momentum compensation point, where the spin density vanishes but the magnetization is finite. Due to the finite magnetostatic energy, a ferrimagnetic disk of suitable geometry can support a vortex as a ground state similar to a ferromagnetic disk. In the vicinity of the angular momentum compensation point, the dynamics of the vortex resemble those of an antiferromagnetic vortex, which is described by equations of motion analogous to Newton's second law for the motion of particles. Owing to the antiferromagnetic nature of the dynamics, the vortex oscillation frequency can be an order of magnitude larger than the frequency of a ferromagnetic vortex, amounting to tens of GHz in common transition-metal based alloys. We show that the frequency can be controlled either by applying an external field or by changing the temperature. In particular, the latter property allows us to detect the angular momentum compensation temperature, at which the lowest eigenfrequency attains its maximum, by performing ferromagnetic resonance measurements on the vortex disk. Our work proposes a ferrimagnetic vortex disk as a tunable source of fast magnetic oscillations and a useful platform to study the properties of ferrimagnets.

  15. Using computer algebra to perform image compression with wavelet transform and SVD

    Science.gov (United States)

    Díaz, Felipe

    2014-05-01

    Computer Algebra Software, especially Maple and its Image Tools package, is used to develop image compression using the Weibull distribution, Wavelet transform application and Singular Value Decomposition (SVD). For prototyping of the image compression process, Maple packages, Linear Algebra, Array Tools and Discrete Transform are used simultaneously with Image Tools image processing package. The image compression process implies the realization of matrix computing with high dimension matrices, and Maple software develops those operations easily and efficiently. Some image compression experiments are done, and the matrix dimension for minimum information needed to store an image is shown clearly, also the matrix dimension of redundant information. Implementation of algorithms for image compression in other computer algebra systems such as Mathematica and Maxima is proposed as future investigation path. Also it is proposed the use of curvelet transform as a tool for image compression,

  16. Chaos in body-vortex interactions

    DEFF Research Database (Denmark)

    Pedersen, Johan Rønby; Aref, Hassan

    2010-01-01

    The model of body–vortex interactions, where the fluid flow is planar, ideal and unbounded, and the vortex is a point vortex, is studied. The body may have a constant circulation around it. The governing equations for the general case of a freely moving body of arbitrary shape and mass density...... and an arbitrary number of point vortices are presented. The case of a body and a single vortex is then investigated numerically in detail. In this paper, the body is a homogeneous, elliptical cylinder. For large body–vortex separations, the system behaves much like a vortex pair regardless of body shape. The case...... of a circle is integrable. As the body is made slightly elliptic, a chaotic region grows from an unstable relative equilibrium of the circle-vortex case. The case of a cylindrical body of any shape moving in fluid otherwise at rest is also integrable. A second transition to chaos arises from the limit between...

  17. Axisymmetric contour dynamics for buoyant vortex rings

    Science.gov (United States)

    Chang, Ching; Llewellyn Smith, Stefan

    2017-11-01

    Vortex rings are important in many fluid flows in engineering and environmental applications. A family of steady propagating vortex rings including thin-core rings and Hill's spherical vortex was obtained by Norbury (1973). However, the dynamics of vortex rings in the presence of buoyancy has not been investigated yet in detail. When the core of a ring is thin, we may formulate reduced equations using momentum balance for vortex filaments, but that is not the case for ``fat'' rings. In our study, we use contour dynamics to study the time evolution of axisymmetric vortex rings when the density of the fluid inside the ring differs from that of the ambient. Axisymmetry leads to an almost-conserved material variable when the Boussinesq approximation is made. A set of integro-differential equations is solved numerically for these buoyant vortex rings. The same physical settings are also used to run a DNS code and compare to the results from contour dynamics.

  18. Scalable fast multipole accelerated vortex methods

    KAUST Repository

    Hu, Qi

    2014-05-01

    The fast multipole method (FMM) is often used to accelerate the calculation of particle interactions in particle-based methods to simulate incompressible flows. To evaluate the most time-consuming kernels - the Biot-Savart equation and stretching term of the vorticity equation, we mathematically reformulated it so that only two Laplace scalar potentials are used instead of six. This automatically ensuring divergence-free far-field computation. Based on this formulation, we developed a new FMM-based vortex method on heterogeneous architectures, which distributed the work between multicore CPUs and GPUs to best utilize the hardware resources and achieve excellent scalability. The algorithm uses new data structures which can dynamically manage inter-node communication and load balance efficiently, with only a small parallel construction overhead. This algorithm can scale to large-sized clusters showing both strong and weak scalability. Careful error and timing trade-off analysis are also performed for the cutoff functions induced by the vortex particle method. Our implementation can perform one time step of the velocity+stretching calculation for one billion particles on 32 nodes in 55.9 seconds, which yields 49.12 Tflop/s.

  19. Electromagnetic Vortex-Based Radar Imaging Using a Single Receiving Antenna: Theory and Experimental Results.

    Science.gov (United States)

    Yuan, Tiezhu; Wang, Hongqiang; Cheng, Yongqiang; Qin, Yuliang

    2017-03-19

    Radar imaging based on electromagnetic vortex can achieve azimuth resolution without relative motion. The present paper investigates this imaging technique with the use of a single receiving antenna through theoretical analysis and experimental results. Compared with the use of multiple receiving antennas, the echoes from a single receiver cannot be used directly for image reconstruction using Fourier method. The reason is revealed by using the point spread function. An additional phase is compensated for each mode before imaging process based on the array parameters and the elevation of the targets. A proof-of-concept imaging system based on a circular phased array is created, and imaging experiments of corner-reflector targets are performed in an anechoic chamber. The azimuthal image is reconstructed by the use of Fourier transform and spectral estimation methods. The azimuth resolution of the two methods is analyzed and compared through experimental data. The experimental results verify the principle of azimuth resolution and the proposed phase compensation method.

  20. Vortex-Induced Vibration Suppression of a Circular Cylinder with Vortex Generators

    Directory of Open Access Journals (Sweden)

    Shi-bo Tao

    2016-01-01

    Full Text Available The vortex-induced vibration is one of the most important factors to make the engineering failure in wind engineering. This paper focuses on the suppression method of vortex-induced vibration that occurs on a circular cylinder fitted with vortex generators, based on the wind tunnel experiment. The effect of the vortex generators is presented with comparisons including the bare cylinder. The experimental results reveal that the vortex generators can efficiently suppress vortex-induced vibration of the circular cylinder. Vortex generator control can make the boundary layer profile fuller and hence more resistant to separation. The selections of skew angles and the angular position have a significant influence on the vortex generator control effect. By correlation analysis, it can be concluded that the vortex generators can inhibit the communication between the two shear layers and produce streamwise vortices to generate a disturbance in the spanwise direction.

  1. Iterative learning control applied to a non-linear vortex panel model for improved aerodynamic load performance of wind turbines with smart rotors

    Science.gov (United States)

    Blackwell, Mark W.; Tutty, Owen R.; Rogers, Eric; Sandberg, Richard D.

    2016-01-01

    The inclusion of smart devices in wind turbine rotor blades could, in conjunction with collective and individual pitch control, improve the aerodynamic performance of the rotors. This is currently an active area of research with the primary objective of reducing the fatigue loads but mitigating the effects of extreme loads is also of interest. The aerodynamic loads on a wind turbine blade contain periodic and non-periodic components and one approach is to consider the application of iterative learning control algorithms. In this paper, the control design is based on a simple, in relative terms, computational fluid dynamics model that uses non-linear wake effects to represent flow past an airfoil. A representation for the actuator dynamics is included to undertake a detailed investigation into the level of control possible and on how performance can be effectively measured.

  2. Performance Evaluation of Frequency Transform Based Block Classification of Compound Image Segmentation Techniques

    Science.gov (United States)

    Selwyn, Ebenezer Juliet; Florinabel, D. Jemi

    2017-12-01

    Compound image segmentation plays a vital role in the compression of computer screen images. Computer screen images are images which are mixed with textual, graphical, or pictorial contents. In this paper, we present a comparison of two transform based block classification of compound images based on metrics like speed of classification, precision and recall rate. Block based classification approaches normally divide the compound images into fixed size blocks of non-overlapping in nature. Then frequency transform like Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) are applied over each block. Mean and standard deviation are computed for each 8 × 8 block and are used as features set to classify the compound images into text/graphics and picture/background block. The classification accuracy of block classification based segmentation techniques are measured by evaluation metrics like precision and recall rate. Compound images of smooth background and complex background images containing text of varying size, colour and orientation are considered for testing. Experimental evidence shows that the DWT based segmentation provides significant improvement in recall rate and precision rate approximately 2.3% than DCT based segmentation with an increase in block classification time for both smooth and complex background images.

  3. Design and performance of a pulse transformer based on Fe-based nanocrystalline core.

    Science.gov (United States)

    Yi, Liu; Xibo, Feng; Lin, Fuchang

    2011-08-01

    A dry-type pulse transformer based on Fe-based nanocrystalline core with a load of 0.88 nF, output voltage of more than 65 kV, and winding ratio of 46 is designed and constructed. The dynamic characteristics of Fe-based nanocrystalline core under the impulse with the pulse width of several microseconds were studied. The pulse width and incremental flux density have an important effect on the pulse permeability, so the pulse permeability is measured under a certain pulse width and incremental flux density. The minimal volume of the toroidal pulse transformer core is determined by the coupling coefficient, the capacitors of the resonant charging circuit, incremental flux density, and pulse permeability. The factors of the charging time, ratio, and energy transmission efficiency in the resonant charging circuit based on magnetic core-type pulse transformer are analyzed. Experimental results of the pulse transformer are in good agreement with the theoretical calculation. When the primary capacitor is 3.17 μF and charge voltage is 1.8 kV, a voltage across the secondary capacitor of 0.88 nF with peak value of 68.5 kV, rise time (10%-90%) of 1.80 μs is obtained.

  4. Vortex chain formation in regions of ion concentration polarization.

    Science.gov (United States)

    Hanasoge, Srinivas; Diez, Francisco J

    2015-09-07

    The local vortical flow generated inside an ion concentration polarization (ICP) region is evaluated experimentally. The ICP is induced by a patterned nanoporous self-assembling membrane integrated inside a single microchannel. A bottom-view image of the depletion region near the membrane revealed a primary vortex which results from the electric field amplification. A unique perspective of the flow is obtained by imaging the microchannel from its side. This visualization shows for the first time the formation of a chain of three vortices all rotating in the same direction in the depletion region. While observation of multiple vortices has been previously reported, it was in reference to counter rotating vortex pairs and not to the same direction of rotating vortex chain formation. A physical model is proposed which considers a two dimensionally varying concentration profile in the depletion region to account for the formation of multiple vortices rotating in the same direction. The fast rotating primary vortex changes the local concentration in regions adjacent to it, as the advection time scale is much higher than the diffusion time scale. Near the membrane, it moves the low concentration electrolyte from the bottom wall upwards into a higher concentration region. Away from the membrane, it moves the high concentration electrolyte from the middle of the channel downwards into a low concentration region. These local changes in the wall concentration result in a varying slip velocity capable of inducing a secondary vortex. Similarly, this secondary vortex can induce a tertiary one. A numerical simulation is performed using the proposed varying slip velocity model which showed excellent agreement with the experimental observations.

  5. The impact of transformational CEOs on the performance of small- to medium-sized firms: does organizational context matter?

    Science.gov (United States)

    Ling, Yan; Simsek, Zeki; Lubatkin, Michael H; Veiga, John F

    2008-07-01

    Although theory suggests that CEOs who engage in transformational leadership should have a positive effect on firm performance, most empirical examinations using data drawn from larger firms have failed to find support for this linkage. Given that the organizational complexity associated with larger firms has been viewed as a central obstacle to establishing this important link, the authors examined the impact of CEO transformational leadership on firm performance in smaller, privately held firms. After first explaining why the less complex context of these firms provides a setting for transformational CEOs to play a more direct role in enhancing firm performance, they then further clarified the nature of this link by hypothesizing 3 contingencies that they argued are particularly salient: firm size, CEO founder status (founder or nonfounder), and CEO tenure. Results from a multisource survey of CEOs and their top management teams in 121 firms and 2 time-lagged measures of performance, 1 objective and 1 perceived, provided consistent support for these hypotheses.

  6. Monitoring the metering performance of an electronic voltage transformer on-line based on cyber-physics correlation analysis

    Science.gov (United States)

    Zhang, Zhu; Li, Hongbin; Tang, Dengping; Hu, Chen; Jiao, Yang

    2017-10-01

    Metering performance is the key parameter of an electronic voltage transformer (EVT), and it requires high accuracy. The conventional off-line calibration method using a standard voltage transformer is not suitable for the key equipment in a smart substation, which needs on-line monitoring. In this article, we propose a method for monitoring the metering performance of an EVT on-line based on cyber-physics correlation analysis. By the electrical and physical properties of a substation running in three-phase symmetry, the principal component analysis method is used to separate the metering deviation caused by the primary fluctuation and the EVT anomaly. The characteristic statistics of the measured data during operation are extracted, and the metering performance of the EVT is evaluated by analyzing the change in statistics. The experimental results show that the method successfully monitors the metering deviation of a Class 0.2 EVT accurately. The method demonstrates the accurate evaluation of on-line monitoring of the metering performance on an EVT without a standard voltage transformer.

  7. Definition of Smart Energy City and State of the art of 6 Transform cities using Key Performance Indicators

    DEFF Research Database (Denmark)

    Nielsen, Per Sieverts; Ben Amer, Sara; Halsnæs, Kirsten

    2013-01-01

    This report summarises the work undertaken under the EU-FP7 TRANSFORM project for Work Package 1 (part 1): Becoming a Smart Energy City, state of the Art and Ambition. Part 1 starts with a clear outline of each of the participating cities. The work describes the context in terms of climate, energy...... assets, ambitions, targets and main possibilities in terms of energy efficiency, flows and energy production. After this first step, the work focuses on the description of what a smart energy city is (this report), what the main Key Performance Indicators (KPIs) are that should be met and how...... will draw largely on existing Strategic Energy Action Plans, Climate Action Plans and planning documents. This report establishes a definition of smart cities develops Key Elements, Key Performance Indicators and reports on the state of the art regarding the KPIs for the 6 Transform cities. As specified...

  8. Evolution of optical vortex distributions in stochastic vortex fields

    CSIR Research Space (South Africa)

    Roux, FS

    2011-01-01

    Full Text Available can to some extent be associated with the orbital angular momentum in the beam.3?5 Various aspects of optical vortices, such as their trajectories6?19 and morphology16, 20?22 have also been studied. However, these studies largely dealt with a small... are caused by variations in the vortex distributions, giving rise to feedback mechanisms and nonlinear behavior. Keywords: Infinitesimal propagation equation, entangle photons, atmospheric turbulence, orbital angular mo- mentum, decoherence 1...

  9. Effect of initial vortex core size on the coherent structures in the swirling jet near field

    Science.gov (United States)

    Rukes, Lothar; Sieber, Moritz; Paschereit, C. Oliver; Oberleithner, Kilian

    2015-10-01

    This study investigates the sensitivity to initial conditions of swirling jets undergoing vortex breakdown. Emphasis is placed on the recirculation bubble and on the helical coherent structures that evolve in its periphery. It is proposed that the vortex core size of the incoming swirling jet is the critical parameter that determines the dynamics of these coherent structures. This proposition is assessed with Stereo Particle-Image-Velocimetry (PIV) measurements of the breakdown region of two swirling jet configurations with different vortex core sizes at very similar overall swirl intensities. The swirling jets were generated by radial vanes entering a mixing tube, and the vortex core size was adjusted by using different center-body geometries. The time-averaged flow fields in the breakdown region reveal substantial differences in the jet spreading and the size of the recirculation bubble. Proper Ortogonal Decomposition (POD) was applied to the anti-axisymmetric and axisymmetric velocity fluctuations, to reconstruct the dynamics of the helical instability and the breakdown bubble, respectively. We find that the mode shape of the helical instability is not affected by the vortex core size. The frequency is found to coincide with the vortex core rotation rate, which relates inversely to the core size. The shape and dynamics of the non-periodic breakdown bubble are significantly affected by a change in vortex core size. The POD reveals that the energy content of the dominant non-periodic structure is changed markedly with the vortex core size. The bubble dynamics are further investigated by tracking the upstream stagnation point from the PIV snapshots. It is shown that a larger vortex core promotes smooth fluctuations of the recirculation bubble, while a small initial vortex core is linked to bimodal fluctuations of the recirculation bubble. The conclusions drawn from this study are relevant for fundamental swirling jet studies, as well as for the design of swirl

  10. Implementation of FFT by using MATLAB: SIMULINK on Xilinx Virtex - 4 FPGAs: Performance of a Paired Transform Based FFT

    OpenAIRE

    Ranganadh Narayanam; Grigoryan, Artyom M.; Bindu Tushara D

    2013-01-01

    Discrete Fourier Transform is principal mathematical method for the frequency analysis and is having wide applications in Engineering and Sciences. Because the DFT is so ubiquitous, fast methods for computing DFT have been studied extensively, and continuous to be an active research. The way of splitting the DFT gives out various fast algorithms. In this paper, we present the implementation of two fast algorithms for the DFT for evaluating their performance. One of them is the popular radix-2...

  11. Performance Of Five Chromatic Adaptation Transforms Using Large Number Of Color Patches

    Directory of Open Access Journals (Sweden)

    Dajana Dordevic

    2009-11-01

    Full Text Available Input devices in general use light sources with different color temperatures. As a consequence, in color acquisition, display and rendering processes a number of chromatic adaptations transforms (CATS are being used. In our study, color transformations between three illuminant source pairs (D50-A, D50-D65 and D65-A were investigated using five cats (Bradford, von Kries, XYZ Scaling, CMCCAT97 and CMCCAT00. Research was made on 8190 color patches that were printed with inkjet printer. Results showed that color differences obtained with the Bradford method were the lowest regardless of the implemented illuminant source pair. The same ranking of CATSwas observed in all combinations of illuminant source pairs, however the smallest color differences were generated with D50-D65 CATS and the biggest with D65-A models.

  12. Performance Of Five Chromatic Adaptation Transforms Using Large Number Of Color Patches

    Directory of Open Access Journals (Sweden)

    Aleš Hladnik

    2009-01-01

    Full Text Available Input devices in general use light sources with different color temperatures. As a consequence, in color acquisition, display and rendering processes a number of chromatic adaptations transforms (cats are being used. In our study, color transformations between three illuminant source pairs (d50-a, d50-d65 and d65-a were investigated using five cats (Bradford, von Kries, xyz Scaling, cmccat97 and cmccat00. Research was made on 8190 color patches that were printed with inkjet printer. Results showed that color differences obtained with the Bradford method were the lowest regardless of the implemented illuminant source pair. The same ranking of cats was observed in all combination of illuminant source pairs, however the smallest color differences were generated with d50-d65 cats and the biggest with d65-a models.

  13. Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

    Directory of Open Access Journals (Sweden)

    Yuzhen Lv

    2017-07-01

    Full Text Available Research on the transformer oil-based nanofluids (NFs has been raised expeditiously over the past decade. Although, there is discrepancy in the stated results and inadequate understanding of the mechanisms of improvement of dielectric nanofluids, these nanofluids have emerged as a potential substitute of mineral oils as insulating and heat removal fluids for high voltage equipment. The transformer oil (TO based magnetic fluids (ferrofluids may be regarded as the posterity insulation fluids as they propose inspiring unique prospectus to improve dielectric breakdown strength, as well as heat transfer efficiency, as compared to pure transformer oils. In this work, transformer oil-based magnetic nanofluids (MNFs are prepared by dispersal of Fe3O4 nanoparticles (MNPs into mineral oil as base oil, with various NPs loading from 5 to 80% w/v. The lightning impulse breakdown voltages (BDV measurement was conducted in accordance with IEC 60897 by using needle to sphere electrodes geometry. The test results showed that dispersion of magnetic NPs may improve the insulation strength of MO. With the increment of NPs concentrations, the positive lightning impulse (LI breakdown strength of TO is first raised, up to the highest value at 40% loading, and then tends to decrease at higher concentrations. The outcomes of negative LI breakdown showed that BDV of MNFs, with numerous loadings, were inferior to the breakdown strength of pure MO. The 40% concentration of nanoparticles (optimum concentration was selected, and positive and negative LI breakdown strength was also further studied at different sizes (10 nm, 20 nm, 30 nm and 40 nm of NPs and different electrode gap distances. Augmentation in the BDV of the ferrofluids (FFs is primarily because of dielectric and magnetic features of Fe3O4 nanoaprticles, which act as electron scavengers and decrease the rate of free electrons produced in the ionization process. Research challenges and technical difficulties

  14. Randomized Unscented Transform in State Estimation of Non-Gaussian Systems: Algorithms and Performance

    Science.gov (United States)

    2012-07-01

    unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 application of local methods, e.g. the Gaussian Sum Filter ( GSF ) consists of...estimation methods was compared in the numerical example: • global filters: – Gaussian sum filter with the RUT ( GSF -RUT), – Gaussian sum filter with...Taylor expansion of the nonlinear equations [4] ( GSF -TE), – Gaussian sum filter with unscented transform [20] ( GSF -UT). • local filters: – EKF, – UKF

  15. OPERATIONAL FACTORS AFFECTING THE PERFORMANCE OF CONTINUOUS MONITORING SYSTEM OF TRANSFORMER EQUIPMENT INSULATION

    Directory of Open Access Journals (Sweden)

    A. G. Spitsa

    2013-07-01

    Full Text Available To ensure the required level of high voltage electrical networks reliability, special attention should be paid to the equipment technical condition monitoring and diagnosis. The periodic monitoring can only reduce the probability of device damaging. The time period between the insulation defect appearance and the device damage can be considerably less than the time interval between measurements recommended by the Testing norms and recommendations for each type of equipment. This demonstrates the lack of effectiveness of the systems of technical diagnostics and large time interval between tests. Continuous monitoring systems are free from these disadvantages. The article covers the results of the insulation continuous monitoring of current transformers and bushings at substation 330 kV «Dnipro-Donbass» Dnieper Power System. Operational factors affecting the reliability of the results are considered, and detailed analysis of errors caused by isolating transformers is given. The article describes methods and recommendations elaborated for mitigation of operational factors impact on the insulation continuous monitoring system. It should be noted that systems of continuous monitoring of transformer equipment under operating voltage are relatively new. Their implementation at the power facilities is at the initial stage. As a result, there is no reliable information on such systems operating experience. Therefore, the investigations covered by this article can be of practical value for both continuous monitoring system developers and operating personnel.

  16. High-performance liquid chromatography/high-resolution mass spectrometry for the characterization of transformation products of ionic liquids.

    Science.gov (United States)

    Fabbri, Debora; Calza, Paola; Noè, Giorgio; Santoro, Valentina; Medana, Claudio

    2017-12-15

    Ionic liquids (ILs) are a subject of active research in the field of alternative solvents. We studied the behaviour of a piperidine IL, 1-butyl-1-methylpiperidinium tetrafluoroborate (BMPA), through the elucidation of its transformation products (TPs) in water. The transformation pathways of BMPA were investigated using high-performance liquid chromatography (HPLC) combined with a hybrid LTQ-Orbitrap instrument on the basis of mass defect filtering. TPs of BMPA were identified by fragmentation patterns and accurate mass measurements. The separation and identification of 32 TPs was achieved. BMPA can be oxidized at different positions in the alkyl chains. The ultimate products corresponds to N-methyl-piperidinium and some byproducts involving ring-opening. Tests of acute toxicity, evaluated with Vibrio Fischeri bacteria, show that BMPA transformation proceeds through the formation of slightly harmful compounds. Results showed that the main transformation pathways of BMPA were alkyl chain hydroxylation/shortening and de-alkylation, and that HPLC/LTQ-Orbitrap can serve as an important analytical platform to gather the unknown TPs of ILs. Copyright © 2017 John Wiley & Sons, Ltd.

  17. Special vortex in relativistic hydrodynamics

    Science.gov (United States)

    Chupakhin, A. P.; Yanchenko, A. A.

    2017-10-01

    An exact solution of the Euler equations governing the flow of a compressible fluid in relativistic hydrodynamics is found and studied. It is a relativistic analogue of the Ovsyannikov vortex (special vortex) investigated earlier for classical gas dynamics. Solutions are partially invariant of Defect 1 and Rank 2 with respect to the rotation group. A theorem on the representation of the factor-system in the form of a union of a non-invariant subsystem for the function determining the deviation of the velocity vector from the meridian, and invariant subsystem for determination of thermodynamic parameters, the Lorentz factor and the radial velocity component is proved. Compatibility conditions for the overdetermined non-invariant subsystem are obtained. A stationary solution of this type is studied in detail. It is proved that its invariant subsystem reduces to an implicit differential equation. For this equation, the manifold of branching of solutions is investigated, and a set of singular points is found.

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

    Science.gov (United States)

    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 ωλ with correlated linear phase (ϕ 0  ≥ 0.025 λ) and lateral shear (y 0  ≥ 0.05 ωλ) 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.

  19. Sub-harmonic frequency lock-in and vortex shedding synchronization due to regular and irregular surface waves.

    Science.gov (United States)

    Gunnoo, Hans; Abcha, Nizar; Bennis, Anne-claire; Levacher, Daniel

    2017-04-01

    The influence of both regular and irregular surface waves on a turbulent Von Karman vortex street has been investigated experimentally with the help of the phase modulation of the signals. The experiments have been performed in a hydrodynamic flume, where the Von Karman Street created behind a vertical cylinder is created by a steady current. The surface waves propagating upstream are excited by a computer controlled wave maker. It is found that the regular surface wave can give rise to different regimes of vortex shedding in the Von Karman Street: Sub-harmonic frequency lock-in arise if the frequency of the wave is approximately two times that of the vortex shedding frequency. We also observed another regime called harmonic frequency lock-in when the shedding frequency coincides with the frequency of the surface wave. Phase synchronization can also be obtained with irregular surface waves. In this case, the peak frequency of the applied surface wave spectrum is twice that of the vortex shedding frequency. The relationship between the vortex shedding frequency and the amplitude of the surface waves has been studied. It was found that an increase in the amplitude of the applied waves causes the shedding frequency to decrease and tends to half of the frequency of the applied wave. For a more detailed study of this effect, Hilbert transformation is applied. Using this transformation, the continuous phases of the surface waves fw and that of the Von Karman vortex street fk are calculated. The relation between the phases combination F= 2fk- fwand the surface wave amplitude is studied. It was found that the time-evolution of F has a step-like shape. The time interval of F having a slope around 0, corresponds to synchronization-like effect. This explains the changes obtained in the spectrum of the turbulent vortex shedding with an increase in the amplitude of the irregular surface waves. We then decided to compare the evolution of the scouring and the sandy patterns

  20. Vortex disruption by magnetohydrodynamic feedback

    Science.gov (United States)

    Mak, J.; Griffiths, S. D.; Hughes, D. W.

    2017-11-01

    In an electrically conducting fluid, vortices stretch out a weak, large-scale magnetic field to form strong current sheets on their edges. Associated with these current sheets are magnetic stresses, which are subsequently released through reconnection, leading to vortex disruption, and possibly even destruction. This disruption phenomenon is investigated here in the context of two-dimensional, homogeneous, incompressible magnetohydrodynamics. We derive a simple order of magnitude estimate for the magnetic stresses—and thus the degree of disruption—that depends on the strength of the background magnetic field (measured by the parameter M , a ratio between the Alfvén speed and a typical flow speed) and on the magnetic diffusivity (measured by the magnetic Reynolds number Rm ). The resulting estimate suggests that significant disruption occurs when M2Rm =O (1 ) . To test our prediction, we analyze direct numerical simulations of vortices generated by the breakup of unstable shear flows with an initially weak background magnetic field. Using the Okubo-Weiss vortex coherence criterion, we introduce a vortex disruption measure, and show that it is consistent with our predicted scaling, for vortices generated by instabilities of both a shear layer and a jet.

  1. Vortex Molecules in Bose-Einstein Condensates

    Science.gov (United States)

    Nitta, Muneto; Eto, Minoru; Cipriani, Mattia

    2014-04-01

    Stable vortex dimers are known to exist in coherently coupled two component Bose-Einstein condensates (BECs). We construct stable vortex trimers in three component BECs and find that the shape can be controlled by changing the internal coherent (Rabi) couplings. Stable vortex N-omers are also constructed in coherently coupled N-component BECs. We classify all possible N-omers in terms of the mathematical graph theory. Next, we study effects of the Rabi coupling in vortex lattices in two-component BECs. We find how the vortex lattices without the Rabi coupling known before are connected to the Abrikosov lattice of integer vortices with increasing the Rabi coupling. In this process, vortex dimers change their partners in various ways at large couplings. We then find that the Abrikosov lattices are robust in three-component BECs.

  2. Review of Idealized Aircraft Wake Vortex Models

    Science.gov (United States)

    Ahmad, Nashat N.; Proctor, Fred H.; Duparcmeur, Fanny M. Limon; Jacob, Don

    2014-01-01

    Properties of three aircraft wake vortex models, Lamb-Oseen, Burnham-Hallock, and Proctor are reviewed. These idealized models are often used to initialize the aircraft wake vortex pair in large eddy simulations and in wake encounter hazard models, as well as to define matched filters for processing lidar observations of aircraft wake vortices. Basic parameters for each vortex model, such as peak tangential velocity and circulation strength as a function of vortex core radius size, are examined. The models are also compared using different vortex characterizations, such as the vorticity magnitude. Results of Euler and large eddy simulations are presented. The application of vortex models in the postprocessing of lidar observations is discussed.

  3. Spin wave mediated magnetic vortex core reversal

    Science.gov (United States)

    Stoll, Hermann

    2012-10-01

    The magnetic vortex is the simplest, non-trivial ground state configuration of micron and sub-micron sized soft magnetic thin film platelets and therefore an interesting subject for the study of micro magnetism. Essential progress in the understanding of nonlinear vortex dynamics was achieved when low-field core toggling was discovered by excitation of the gyrotropic eigenmode at sub-GHz frequencies. At frequencies more than an order of magnitude higher vortex state structures possess spin wave eigenmodes arising from the magneto-static interaction. We demonstrated, experimentally and by micromagnetic simulations, that the unidirectional vortex core reversal process also occurs when azimuthal spin wave modes are excited in the multi-GHz frequency range. This finding highlights the importance of spin wave - vortex interaction and boosts vortex core reversal to much higher frequencies, which may offer new routes for GHz spintronics applications.

  4. Vortex dynamics in nonrelativistic Abelian Higgs model

    Directory of Open Access Journals (Sweden)

    A.A. Kozhevnikov

    2015-11-01

    Full Text Available The dynamics of the gauge vortex with arbitrary form of a contour is considered in the framework of the nonrelativistic Abelian Higgs model, including the possibility of the gauge field interaction with the fermion asymmetric background. The equations for the time derivatives of the curvature and the torsion of the vortex contour generalizing the Betchov–Da Rios equations in hydrodynamics, are obtained. They are applied to study the conservation of helicity of the gauge field forming the vortex, twist, and writhe numbers of the vortex contour. It is shown that the conservation of helicity is broken when both terms in the equation of the vortex motion are present, the first due to the exchange of excitations of the phase and modulus of the scalar field and the second one due to the coupling of the gauge field forming the vortex, with the fermion asymmetric background.

  5. Topology of Vortex-Wing Interaction

    Science.gov (United States)

    McKenna, Chris; Rockwell, Donald

    2016-11-01

    Aircraft flying together in an echelon or V formation experience aerodynamic advantages. Impingement of the tip vortex from the leader (upstream) wing on the follower wing can yield an increase of lift to drag ratio. This enhancement is known to depend on the location of vortex impingement on the follower wing. Particle image velocimetry is employed to determine streamline topology in successive crossflow planes, which characterize the streamwise evolution of the vortex structure along the chord of the follower wing and into its wake. Different modes of vortex-follower wing interaction are created by varying both the spanwise and vertical locations of the leader wing. These modes are defined by differences in the number and locations of critical points of the flow topology, and involve bifurcation, attenuation, and mutual induction. The bifurcation and attenuation modes decrease the strength of the tip vortex from the follower wing. In contrast, the mutual induction mode increases the strength of the follower tip vortex. AFOSR.

  6. Fatigue performance of superelastic NiTi near stress-induced martensitic transformation

    Czech Academy of Sciences Publication Activity Database

    Alarcón Tarquino, Eduardo; Heller, Luděk; Chirani, S.A.; Šittner, Petr; Kopeček, Jaromír; Saint-Sulpice, L.; Calloch, S.

    2017-01-01

    Roč. 95, Feb (2017), s. 76-89 ISSN 0142-1123 R&D Projects: GA ČR GB14-36566G; GA MŠk LO1409; GA MŠk LM2015088; GA ČR GA16-20264S; GA ČR GA14-15264S Grant - others:FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 Keywords : shape-memory alloys * Nitinol * superelasticity * martensitic transformation * shape memory alloys * fatigue Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.899, year: 2016

  7. Diagnostics of spatial structure of vortex multiplets in a swirl flow

    DEFF Research Database (Denmark)

    Naumov, I. V.; Okulov, Valery; Sørensen, Jens Nørkær

    2011-01-01

    Results on investigation of vortex unstable breakdown are presented. The structure of vortex multiplets was visualized in a vertical cylindrical container made of transparent organic glass of the optic quality with the inner diameter of 288 mm and rotating upper lid. Visualization was performed f....... Visualization of flow structure for unstable swirl flows and cylinder aspect ratios from 3.2 to 5.5 allowed first identification of these regimes as multispiral breakdowns with formation of helical-like vortex duplets, triplets and quadruplets....

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

    Science.gov (United States)

    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.

  9. Robust numerical method for integration of point-vortex trajectories in two dimensions

    Science.gov (United States)

    Smith, Spencer A.; Boghosian, Bruce M.

    2011-05-01

    The venerable two-dimensional (2D) point-vortex model plays an important role as a simplified version of many disparate physical systems, including superfluids, Bose-Einstein condensates, certain plasma configurations, and inviscid turbulence. This system is also a veritable mathematical playground, touching upon many different disciplines from topology to dynamic systems theory. Point-vortex dynamics are described by a relatively simple system of nonlinear ordinary differential equations which can easily be integrated numerically using an appropriate adaptive time stepping method. As the separation between a pair of vortices relative to all other intervortex length scales decreases, however, the computational time required diverges. Accuracy is usually the most discouraging casualty when trying to account for such vortex motion, though the varying energy of this ostensibly Hamiltonian system is a potentially more serious problem. We solve these problems by a series of coordinate transformations: We first transform to action-angle coordinates, which, to lowest order, treat the close pair as a single vortex amongst all others with an internal degree of freedom. We next, and most importantly, apply Lie transform perturbation theory to remove the higher-order correction terms in succession. The overall transformation drastically increases the numerical efficiency and ensures that the total energy remains constant to high accuracy.

  10. Excitation of vortex meandering in shear flow

    OpenAIRE

    Schröttle, Josef; Dörnbrack, Andreas; Schumann, Ulrich

    2015-01-01

    This paper investigates the evolution of a streamwise aligned columnar vortex with vorticity ω in an axial background shear of magnitude Ω by means of linear stability analysis and numerical simulations. A long wave mode of vorticity normal to the plane spanned by the background shear vector Ω and the vorticity of the vortex are excited by an instability. The stationary wave modes of the vertical and lateral vorticity are amplified. In order to form a helical vortex, the lat...

  11. Optical Vortex Solitons in Parametric Wave Mixing

    OpenAIRE

    Alexander, Tristram J.; Kivshar, Yuri S.; Buryak, Alexander V.; Sammut, Rowland A.

    1999-01-01

    We analyze two-component spatial optical vortex solitons supported by parametric wave mixing processes in a nonlinear bulk medium. We study two distinct cases of such localised waves, namely, parametric vortex solitons due to phase-matched second-harmonic generation in an optical medium with competing quadratic and cubic nonlinear response, and vortex solitons in the presence of third-harmonic generation in a cubic medium. We find, analytically and numerically, the structure of two-component ...

  12. Resolution performance of the fast Pade transform: Potential advantages for magnetic resonance spectroscopy in ovarian cancer diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Belkic, Karen [Department of Oncology/Pathology, Karolinska Institute, Stockholm (Sweden); Institute for Prevention Research, University of Southern California Keck School of Medicine, Los Angeles, CA (United States)], E-mail: Karen.Belkic@ki.se

    2007-10-01

    We examine the resolution performance of the fast Pade transform (FPT) applied to theoretically generated (synthesized) noiseless time signals that are reminiscent of in vitro magnetic resonance spectroscopy (MRS) data as encoded from benign and malignant ovarian cyst fluid at strong magnetic fields. All the input spectral parameters were reconstructed exactly by the FPT using only N/16=64 signal points out of N=1024 sampled data. The resulting Pade absorption spectra exhibit all the unequivocally resolved metabolites that are inherent in the input time signal. The present study reveals the potential of the FPT to reliably as well as accurately quantify and split apart closely lying resonances with a very small number of signal points, over two orders of magnitude fewer than with the conventional fast Fourier transform. These features of the FPT could be of potential benefit for ovarian cancer diagnostics via MRS.

  13. AC electric field induced vortex in laminar coflow diffusion flames

    KAUST Repository

    Xiong, Yuan

    2014-09-22

    Experiments were performed by applying sub-critical high-voltage alternating current (AC) to the nozzle of laminar propane coflow diffusion flames. Light scattering, laser-induced incandescence and laser-induced fluorescence techniques were used to identify the soot zone, and the structures of OH and polycyclic aromatic hydrocarbons (PAHs). Particle image velocimetry was adopted to quantify the velocity field. Under certain AC conditions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered, leading to the formation of toroidal vortices. Increased residence time and heat recirculation inside the vortex resulted in appreciable formation of PAHs and soot near the nozzle exit. Decreased residence time along the jet axis through flow acceleration by the vortex led to a reduction in the soot volume fraction in the downstream sooting zone. Electromagnetic force generated by AC was proposed as a viable mechanism for the formation of the toroidal vortex. The onset conditions for the vortex formation supported the role of an electromagnetic force acting on charged particles in the flame zone. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  14. Simulation of Wake Vortex Radiometric Detection via Jet Exhaust Proxy

    Science.gov (United States)

    Daniels, Taumi S.

    2015-01-01

    This paper describes an analysis of the potential of an airborne hyperspectral imaging IR instrument to infer wake vortices via turbine jet exhaust as a proxy. The goal was to determine the requirements for an imaging spectrometer or radiometer to effectively detect the exhaust plume, and by inference, the location of the wake vortices. The effort examines the gas spectroscopy of the various major constituents of turbine jet exhaust and their contributions to the modeled detectable radiance. Initially, a theoretical analysis of wake vortex proxy detection by thermal radiation was realized in a series of simulations. The first stage used the SLAB plume model to simulate turbine jet exhaust plume characteristics, including exhaust gas transport dynamics and concentrations. The second stage used these plume characteristics as input to the Line By Line Radiative Transfer Model (LBLRTM) to simulate responses from both an imaging IR hyperspectral spectrometer or radiometer. These numerical simulations generated thermal imagery that was compared with previously reported wake vortex temperature data. This research is a continuation of an effort to specify the requirements for an imaging IR spectrometer or radiometer to make wake vortex measurements. Results of the two-stage simulation will be reported, including instrument specifications for wake vortex thermal detection. These results will be compared with previously reported results for IR imaging spectrometer performance.

  15. ASRS Reports on Wake Vortex Encounters

    Science.gov (United States)

    Connell, Linda J.; Taube, Elisa Ann; Drew, Charles Robert; Barclay, Tommy Earl

    2010-01-01

    ASRS is conducting a structured callback research project of wake vortex incidents reported to the ASRS at all US airports, as well as wake encounters in the enroute environment. This study has three objectives: (1) Utilize the established ASRS supplemental data collection methodology and provide ongoing analysis of wake vortex encounter reports; (2) Document event dynamics and contributing factors underlying wake vortex encounter events; and (3) Support ongoing FAA efforts to address pre-emptive wake vortex risk reduction by utilizing ASRS reporting contributions.

  16. Ring vortex solitons in nonlocal nonlinear media

    DEFF Research Database (Denmark)

    Briedis, D.; Petersen, D.E.; Edmundson, D.

    2005-01-01

    We study the formation and propagation of two-dimensional vortex solitons, i.e. solitons with a phase singularity, in optical materials with a nonlocal focusing nonlinearity. We show that nonlocality stabilizes the dynamics of an otherwise unstable vortex beam. This occurs for either single...... or higher charge fundamental vortices as well as higher order (multiple ring) vortex solitons. Our results pave the way for experimental observation of stable vortex rings in other nonlocal nonlinear systems including Bose-Einstein condensates with pronounced long-range interparticle interaction....

  17. Vortex molecules in Bose-Einstein condensates

    OpenAIRE

    Nitta, Muneto; Eto, Minoru; Cipriani, Mattia

    2013-01-01

    Stable vortex dimers are known to exist in coherently coupled two component Bose-Einstein condensates (BECs). We construct stable vortex trimers in three component BECs and find that the shape can be controlled by changing the internal coherent (Rabi) couplings. Stable vortex N-omers are also constructed in coherently coupled N-component BECs. We classify all possible N-omers in terms of the mathematical graph theory. Next, we study effects of the Rabi coupling in vortex lattices in two-compo...

  18. Spin transport in tilted electron vortex beams

    OpenAIRE

    Basu, Banasri; Chowdhury, Debashree

    2016-01-01

    In this paper we have enlightened the spin related issues of tilted Electron vortex beams. We have shown that in the skyrmionic model of electron we can have the spin Hall current considering the tilted type of electron vortex beam. We have considered the monopole charge of the tilted vortex as time dependent and through the time variation of the monopole charge we can explain the spin Hall effect of electron vortex beams. Besides, with an external magnetic field we can have a spin filter con...

  19. Energy dynamics of the intraventricular vortex after mitral valve surgery.

    Science.gov (United States)

    Nakashima, Kouki; Itatani, Keiichi; Kitamura, Tadashi; Oka, Norihiko; Horai, Tetsuya; Miyazaki, Shohei; Nie, Masaki; Miyaji, Kagami

    2017-09-01

    Mitral valve morphology after mitral valve surgery affects postoperative intraventricular flow patterns and long-term cardiac performance. We visualized ventricular flow by echocardiography vector flow mapping (VFM) to reveal the impact of different mitral valve procedures. Eleven cases of mechanical mitral valve replacement (nine in the anti-anatomical and two in the anatomical position), three bioprosthetic mitral valve replacements, and four mitral valve repairs were evaluated. The mean age at the procedure was 57.4 ± 17.8 year, and the echocardiography VFM in the apical long-axis view was performed 119.9 ± 126.7 months later. Flow energy loss (EL), kinetic pressure (KP), and the flow energy efficiency ratio (EL/KP) were measured. The cases with MVR in the anatomical position and with valve repair had normal vortex directionality ("Clockwise"; N = 6), whereas those with MVR in the anti-anatomical position and with a bioprosthetic mitral valve had the vortex in the opposite direction ("Counterclockwise"; N = 12). During diastole, vortex direction had no effect on EL ("Clockwise": 0.080 ± 0.025 W/m; "Counterclockwise": 0.083 ± 0.048 W/m; P = 0.31) or KP ("Clockwise": 0.117 ± 0.021 N; "Counterclockwise": 0.099 ± 0.057 N; P = 0.023). However, during systole, the EL/KP ratio was significantly higher in the "Counterclockwise" vortex than that in the "Clockwise" vortex (1.056 ± 0.463 vs. 0.617 ± 0.158; P = 0.009). MVP and MVR with a mechanical valve in the anatomical position preserve the physiological vortex, whereas MVR with a mechanical valve in the anti-anatomical position and a bioprosthetic mitral valve generate inefficient vortex flow patterns, resulting in a potential increase in excessive cardiac workload.

  20. Non-topological Vortex Configurations in the ABJM Model

    Science.gov (United States)

    Han, Xiaosen; Tarantello, Gabriella

    2017-05-01

    In this paper we study the existence of vortex-type solutions for a system of self-dual equations deduced from the mass-deformed Aharony-Bergman-Jafferis-Maldacena (ABJM) model. The governing equations, derived by Mohammed, Murugan, and Nastse under suitable ansatz involving fuzzy sphere matrices, have the new feature that they can support only non-topological vortex solutions. After transforming the self-dual equations into a nonlinear elliptic {2× 2} system we prove first an existence result by means of a perturbation argument based on a new and appropriate scaling for the solutions. Subsequently, we prove a more complete existence result by using a dynamical analysis together with a blow-up argument. In this way we establish that any positive energy level is attained by a 1-parameter family of vortex solutions, which also correspond to (constraint) energy minimizers. In other words, we register the exceptional fact in a BPS-setting that, neither a "quantization" effect nor an energy gap is induced upon the system by the rigid "critical" coupling of the self-dual regime.

  1. Linking Job-Relevant Personality Traits, Transformational Leadership, and Job Performance via Perceived Meaningfulness at Work: A Moderated Mediation Model.

    Science.gov (United States)

    Frieder, Rachel E; Wang, Gang; Oh, In-Sue

    2017-10-09

    By integrating the fundamental principles of the theory of purposeful work behavior (TPWB; Barrick, Mount, & Li, 2013) with cognitive-affective personality system (CAPS) theory (Mischel, 1977; Mischel & Shoda, 1995), we examine how and when salespeople's job-relevant personality traits relate to their performance. We argue that individuals with personality traits that fit outdoor sales jobs (i.e., conscientious, extraversion, openness to experience) will perceive their work as more meaningful and as a result achieve heightened performance. Moreover, drawing from TPWB and CAPS theory, we expect that as an important element of the social context, transformational leadership moderates the indirect effect of salespeople's job-relevant personality traits on their job performance via enhanced perceptions of meaningfulness at work. Results based on data from 496 outdoor salespeople and their 218 supervisors and regional managers provide support for the hypotheses pertaining to conscientiousness and openness, but not extraversion. Specifically, the conditional indirect effects of conscientiousness or openness on performance through perceived meaningfulness are more positive under low, rather than high, levels of transformational leadership. Implications for research and practice are discussed along with study limitations and future research directions. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  2. Particle-vortex duality in topological insulators and superconductors

    Science.gov (United States)

    Murugan, Jeff; Nastase, Horatiu

    2017-05-01

    We investigate the origins and implications of the duality between topological insulators and topological superconductors in three and four spacetime dimensions. In the latter, the duality transformation can be made at the level of the path integral in the standard way, while in three dimensions, it takes the form of "self-duality in odd dimensions". In this sense, it is closely related to the particle-vortex duality of planar systems. In particular, we use this to elaborate on Son's conjecture that a three dimensional Dirac fermion that can be thought of as the surface mode of a four dimensional topological insulator is dual to a composite fermion.

  3. Stability of transgene expression, field performance and recombination breeding of transformed barley lines

    DEFF Research Database (Denmark)

    Horvath, H.; Jensen, L.G.; Wong, O.T.

    2001-01-01

    originated from three independent primary transformants obtained by the biolistic method with three plasmids containing respectively, the bar gene, the uidA gene and the gene for a protein-engineered heat-stable (1,3-1,4)-beta -glucanase. Three production levels of recombinant beta -glucanase were identified......-grain weight as well as variable yield depressions compared to the Golden Promise progenitor. In 1999 large-scale propagations of the lines with the highest recombinant enzyme synthesis during germination and of Golden Promise were studied at three different locations. Tn an irrigated field transgenic...... lines yielded approximately 6 t.ha(-1) and Golden Promise 7.7 t.ha(-1). Cross-breeding was carried out to transfer the transgene into a more suitable genetic background. Crosses of the semi-dwarf ari-e mutant Golden Promise gave rise to the four morphological phenotypes nutans, high erect, erect...

  4. Transforming the existing building stock to high performed energy efficient and experienced architecture

    DEFF Research Database (Denmark)

    Vestergaard, Inge

    The project Sustainable Renovation examines the challenge of the current and future architectural renovation of Danish suburbs which were designed in the period from 1945 to 1973. The research project takes its starting point in the perspectives of energy optimization and the fact that the building...... architectural heritage to energy efficiency and from architectural quality to sustainability. The first, second and third renovations are discussed from financial and sustainable view points. The role of housing related to the public energy supply system and the relation between the levels of renovation...... process over the period changed from craftsmanship to industrialized production of housing. The aim is to present the context in which energy transformation has to be seen as an architectural question. The research field focuses on social housing blocks and expands the discussion of architecture from...

  5. Quantification of transport across the boundary of the lower stratospheric vortex during Arctic winter 2002/2003

    Directory of Open Access Journals (Sweden)

    G. Günther

    2008-07-01

    Full Text Available Strong perturbations of the Arctic stratosphere during the winter 2002/2003 by planetary waves led to enhanced stretching and folding of the vortex. On two occasions the vortex in the lower stratosphere split into two secondary vortices that re-merged after some days. As a result of these strong disturbances the role of transport in and out of the vortex was stronger than usual. An advection and mixing simulation with the Chemical Lagrangian Model of the Stratosphere (CLaMS utilising a suite of inert tracers tagging the original position of the air masses has been carried out. The results show a variety of synoptic and small scale features in the vicinity of the vortex boundary, especially long filaments peeling off the vortex edge and being slowly mixed into the mid latitude environment. The vortex folding events, followed by re-merging of different parts of the vortex led to strong filamentation of the vortex interior. During January, February, and March 2003 flights of the Russian high-altitude aircraft Geophysica were performed in order to probe the vortex, filaments and in one case the merging zone between the secondary vortices. Comparisons between CLaMS results and observations obtained from the Geophysica flights show in general good agreement.

    Several areas affected by both transport and strong mixing could be identified, allowing explanation of many of the structures observed during the flights. Furthermore, the CLaMS simulations allow for a quantification of the air mass exchange between mid latitudes and the vortex interior. The simulation suggests that after the formation of the vortex was completed, its interior remaind relatively undisturbed. Only during the two re-merging events were substantial amounts of extra-vortex air transported into the polar vortex. When in March the vortex starts weakening additional influence from lower latitudes becomes apparent in the model results.

    In the lower stratosphere export

  6. Vortex statistics in turbulent channel flows

    Science.gov (United States)

    Elsas, José Hugo; Augusto Moriconi, Luca Roberto

    2016-11-01

    In order to address the role of coherent structures in wall bounded turbulence, we study the statistics of morphological and kinematic properties of vortices, such as circulation, radius and height distributions. To accomplish that, we introduce a novel vortex identification method named as "vorticity curvature criterion" which is based on the local properties of the vorticity field. We furthermore employ a background subtraction procedure to remove shearing background effects expected to be present in the topology of the streamwise/wall-normal plane flow configurations. We discuss, through a comparative study of performance with the usual swirling strength criterion, and extending the previous analyses to the detection of coherent structures in the spanwise/wall normal planes, isotropization issues for the paradigmatic case of numerical turbulent channel flows. We acknowledge the funding from CNPq, CAPES and Faperj.

  7. Vortex diffusion and vortex-line hysteresis in radial quantum turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Saluto, L., E-mail: lidia.saluto@unipa.it [DEIM, Università degli Studi di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Jou, D., E-mail: david.jou@uab.es [Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Mongiovi, M.S., E-mail: m.stella.mongiovi@unipa.it [DEIM, Università degli Studi di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

    2014-05-01

    We study the influence of vortex diffusion on the evolution of inhomogeneous quantized vortex tangles. A simple hydrodynamical model to describe inhomogeneous counterflow superfluid turbulence is used. As an illustration, we obtain solutions for these effects in radial counterflow of helium II between two concentric cylinders at different temperatures. The vortex diffusion from the inner hotter cylinder to the outer colder cylinder increases the vortex length density everywhere as compared with the non-diffusive situation. The possibility of hysteresis in the vortex line density under cyclical variations of the heat flow is explored.

  8. Experimental investigations of on-demand vortex generators

    Science.gov (United States)

    Saddoughi, Seyed G.

    1994-12-01

    Conventional vortex generators as found on many civil aircrafts are mainly for off-design conditions - e.g. suppression of separation or loss of aileron power when the Mach number accidentally rises above the design (cruise) value. In normal conditions they perform no useful function and exert a significant drag penalty. Recently there have been advances in new designs for passive vortex generators and boundary layer control. While traditionally the generators heights were of the order of the boundary layer thickness (delta), recent advances have been made where generators of the order of delta/4 have been shown to be effective. The advancement of MIcro-Electro-Mechanical (MEM) devices has prompted several efforts in exploring the possibility of using such devices in turbulence control. These new devices offer the possibility of boundary layer manipulation through the production of vortices, momentum jets, or other features in the flow. However, the energy output of each device is low in general, but they can be used in large numbers. Therefore, the possibility of moving from passive vortex generators to active (on-demand) devices becomes of interest. Replacement of fixed rectangular or delta-wing generators by devices that could be activated when needed would produce substantial economies. Our proposed application is not strictly 'active' control: the vortex generators would simply be switched on, all together, when needed (e.g. when the aircraft Mach number exceeded a certain limit). To this extent our scheme is simpler; however, to promote mixing and suppress separation we desire to deposit longitudinal vortices into the outer layer of the boundary layer as in conventional vortex generators. This requires a larger device although an alternative might be an array of smaller devices, for example, a longitudinal row with phase differences in the modulation signals so that the periodic vortices join up. The vortex pair with common flow up has the advantage that it

  9. Vortex identification from local properties of the vorticity field

    Science.gov (United States)

    Elsas, J. H.; Moriconi, L.

    2017-01-01

    A number of systematic procedures for the identification of vortices/coherent structures have been developed as a way to address their possible kinematical and dynamical roles in structural formulations of turbulence. It has been broadly acknowledged, however, that vortex detection algorithms, usually based on linear-algebraic properties of the velocity gradient tensor, can be plagued with severe shortcomings and may become, in practical terms, dependent on the choice of subjective threshold parameters in their implementations. In two-dimensions, a large class of standard vortex identification prescriptions turn out to be equivalent to the "swirling strength criterion" (λc i-criterion), which is critically revisited in this work. We classify the instances where the accuracy of the λc i-criterion is affected by nonlinear superposition effects and propose an alternative vortex detection scheme based on the local curvature properties of the vorticity graph (x ,y ,ω ) —the "vorticity curvature criterion" (λω-criterion)—which improves over the results obtained with the λc i-criterion in controlled Monte Carlo tests. A particularly problematic issue, given its importance in wall-bounded flows, is the eventual inadequacy of the λc i-criterion for many-vortex configurations in the presence of strong background shear. We show that the λω-criterion is able to cope with these cases as well, if a subtraction of the mean velocity field background is performed, in the spirit of the Reynolds decomposition procedure. A realistic comparative study for vortex identification is then carried out for a direct numerical simulation of a turbulent channel flow, including a three-dimensional extension of the λω-criterion. In contrast to the λc i-criterion, the λω-criterion indicates in a consistent way the existence of small scale isotropic turbulent fluctuations in the logarithmic layer, in consonance with long-standing assumptions commonly taken in turbulent boundary

  10. Vortex stretching in self-gravitating protoplanetary discs

    Science.gov (United States)

    Regály, Zs.; Vorobyov, E.

    2017-10-01

    Horseshoe-shaped brightness asymmetries of several transitional discs are thought to be caused by large-scale vortices. Anticyclonic vortices efficiently collect dust particles, therefore they can play a major role in planet formation. Former studies suggest that the disc self-gravity weakens vortices formed at the edge of the gap opened by a massive planet in discs whose masses are in the range of 0.01 ≤ Mdisc/M* ≤ 0.1. Here, we present an investigation on the long-term evolution of the large-scale vortices formed at the viscosity transition of the discs' dead zone outer edge by means of two-dimensional hydrodynamic simulations taking disc self-gravity into account. We perform a numerical study of low-mass, 0.001 ≤ Mdisc/M* ≤ 0.01, discs, for which cases disc self-gravity was previously neglected. The large-scale vortices are found to be stretched due to disc self-gravity even for low-mass discs with Mdisc/M* ≳ 0.005, where initially the Toomre Q-parameter was ≲ 50 at the vortex distance. As a result of stretching, the vortex aspect ratio increases and a weaker azimuthal density contrast develops. The strength of the vortex stretching is proportional to the disc mass. The vortex stretching can be explained by a combined action of a non-vanishing gravitational torque caused by the vortex and the Keplerian shear of the disc. Self-gravitating vortices are subject to significantly faster decay than non-self-gravitating ones. We found that vortices developed at sharp viscosity transitions of self-gravitating discs can be described by a Goodman - Narayan - Goldreich (GNG) model as long as the disc viscosity is low, I.e. αdz ≤ 10-5.

  11. Parallelization of the AliRoot event reconstruction by performing a semi- automatic source-code transformation

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    side bus or processor interconnections. Parallelism can only result in performance gain, if the memory usage is optimized, memory locality improved and the communication between threads is minimized. But the domain of concurrent programming has become a field for highly skilled experts, as the implementation of multithreading is difficult, error prone and labor intensive. A full re-implementation for parallel execution of existing offline frameworks, like AliRoot in ALICE, is thus unaffordable. An alternative method, is to use a semi-automatic source-to-source transformation for getting a simple parallel design, with almost no interference between threads. This reduces the need of rewriting the develop...

  12. AN INVESTIGATION OF THE EFFECT OF THE HOT END PLUGS ON THE EFFICIENCY OF THE RANQUE-HILSCH VORTEX TUBE

    Directory of Open Access Journals (Sweden)

    MAZIAR ARJOMANDI

    2007-12-01

    Full Text Available The phenomenon of temperature distribution in confined steady rotating gas flows is called Ranque-Hilsch effect. The simple counter-flow vortex tube consists of a long hollow cylinder with tangential nozzle at one end for injecting compressed air. The flow inside the vortex tube can be described as rotating air, which moves in a spring-shaped vortex track. The peripheral flow moves toward the hot end where a hot end plug is placed and the axial flow, which is forced back by the plug, moves in the opposite direction toward the cold end. This paper focuses on the effect of the size of hot nozzle on the performance of the Ranque–Hilsch vortex tube. Series of plugs were used in the experiment in order to find the relationship between the diameter of hot end plug and the performance of the vortex tube.

  13. A New Bond Albedo for Performing Orbital Debris Brightness to Size Transformations

    Science.gov (United States)

    Mulrooney, Mark K.; Matney, Mark J.

    2008-01-01

    We have developed a technique for estimating the intrinsic size distribution of orbital debris objects via optical measurements alone. The process is predicated on the empirically observed power-law size distribution of debris (as indicated by radar RCS measurements) and the log-normal probability distribution of optical albedos as ascertained from phase (Lambertian) and range-corrected telescopic brightness measurements. Since the observed distribution of optical brightness is the product integral of the size distribution of the parent [debris] population with the albedo probability distribution, it is a straightforward matter to transform a given distribution of optical brightness back to a size distribution by the appropriate choice of a single albedo value. This is true because the integration of a powerlaw with a log-normal distribution (Fredholm Integral of the First Kind) yields a Gaussian-blurred power-law distribution with identical power-law exponent. Application of a single albedo to this distribution recovers a simple power-law [in size] which is linearly offset from the original distribution by a constant whose value depends on the choice of the albedo. Significantly, there exists a unique Bond albedo which, when applied to an observed brightness distribution, yields zero offset and therefore recovers the original size distribution. For physically realistic powerlaws of negative slope, the proper choice of albedo recovers the parent size distribution by compensating for the observational bias caused by the large number of small objects that appear anomalously large (bright) - and thereby skew the small population upward by rising above the detection threshold - and the lower number of large objects that appear anomalously small (dim). Based on this comprehensive analysis, a value of 0.13 should be applied to all orbital debris albedo-based brightness-to-size transformations regardless of data source. Its prima fascia genesis, derived and constructed

  14. Fire Whirls, Vortex Breakdown(?), and Blue Whirls

    Science.gov (United States)

    Oran, Elaine; Xiao, Huahua; Gollner, Michael

    2016-11-01

    As we were investigating the efficiency of fire-whirl burning on water, we observed the usual transformation of a pool fire to a fire whirl, and then suddenly, we saw the fire undergo a third transition. A blue cup appeared around the base of the fire whirl, surrounding the yellow flame, the yellow flame receded into the cup and finally disappeared. What remained was a small, rapidly spinning blue flame that burned until the fuel on the water was consumed. The blue whirl was shaped like a spinning cup, closed at the bottom near the water surface, and spreading in radius moving upwards towards the rim. Above the blue cup lip, there was a purple cone-shaped mist. The fuel was usually n-heptane, but at one point it was crude oil, and still the blue whirl formed naturally. The height of the fire whirl on the laboratory pan was larger than a half meter, and this evolved into a blue whirl about 4-8 cm high. Occasionally the blue whirl would become "unstable" and revert to a transitional state of blue cup holding a yellow flame. When the blue whirl formed, turbulence seemed to disappear, and the flame became quiet. We will show videos of how this happened and discuss the evolution of the fire whirl to the blue whirl in vortex-breakdown concepts. This work was supported by and EAGER award from NSF and Minta Martin Endowment Funds in the Department of Aerospace Engineering at the University of Maryland.

  15. Organizational structure and performance – a predictive study on the transformation of the Romanian public universities

    Directory of Open Access Journals (Sweden)

    Băcanu, B.

    2011-01-01

    Full Text Available An administrative restructuring of universities is considered to be necessary for improving the performance of Romanian higher education. Broadly speaking, a positive impact is expected due to the augmentation of organizational entities, the “best tool” being the department. The present study assesses the possibility of positive expected trend in performance, analyzing the causal relation between organizational structure and performance. The deductive analysis uses some referential theoretic works and also some empirical well-known evidence from the Western private and public sector.

  16. Vortex dynamics in thin elliptic ferromagnetic nanodisks

    Science.gov (United States)

    Wysin, G. M.

    2015-10-01

    Vortex gyrotropic motion in thin ferromagnetic nanodisks of elliptical shape is described here for a pure vortex state and for a situation with thermal fluctuations. The system is analyzed using numerical simulations of the Landau-Lifshitz-Gilbert (LLG) equations, including the demagnetization field calculated with a Green's function approach for thin film problems. At finite temperature the thermalized dynamics is found using a second order Heun algorithm for a magnetic Langevin equation based on the LLG equations. The vortex state is stable only within a limited range of ellipticity, outside of which a quasi-single-domain becomes the preferred minimum energy state. A vortex is found to move in an elliptical potential, whose force constants along the principal axes are determined numerically. The eccentricity of vortex motion is directly related to the force constants. Elliptical vortex motion is produced spontaneously by thermal fluctuations. The vortex position and velocity distributions in thermal equilibrium are Boltzmann distributions. The results show that vortex motion in elliptical disks can be described by a Thiele equation.

  17. Flow field measurement around vortex cavitation

    NARCIS (Netherlands)

    Pennings, P.C.; Westerweel, J.; Van Terwisga, T.J.C.

    2015-01-01

    Models for the center frequency of cavitating-vortex induced pressure-fluctuations, in a flow around propellers, require knowledge of the vortex strength and vapor cavity size. For this purpose, stereoscopic particle image velocimetry (PIV) measurements were taken downstream of a fixed half-wing

  18. The modelling of symmetric airfoil vortex generators

    Science.gov (United States)

    Reichert, B. A.; Wendt, B. J.

    1996-01-01

    An experimental study is conducted to determine the dependence of vortex generator geometry and impinging flow conditions on shed vortex circulation and crossplane peak vorticity for one type of vortex generator. The vortex generator is a symmetric airfoil having a NACA 0012 cross-sectional profile. The geometry and flow parameters varied include angle-of-attack alfa, chordlength c, span h, and Mach number M. The vortex generators are mounted either in isolation or in a symmetric counter-rotating array configuration on the inside surface of a straight pipe. The turbulent boundary layer thickness to pipe radius ratio is delta/R = 0. 17. Circulation and peak vorticity data are derived from crossplane velocity measurements conducted at or about 1 chord downstream of the vortex generator trailing edge. Shed vortex circulation is observed to be proportional to M, alfa, and h/delta. With these parameters held constant, circulation is observed to fall off in monotonic fashion with increasing airfoil aspect ratio AR. Shed vortex peak vorticity is also observed to be proportional to M, alfa, and h/delta. Unlike circulation, however, peak vorticity is observed to increase with increasing aspect ratio, reaching a peak value at AR approx. 2.0 before falling off.

  19. Formation of Ion Phase-Space Vortexes

    DEFF Research Database (Denmark)

    Pécseli, Hans; Trulsen, J.; Armstrong, R. J.

    1984-01-01

    for their initial evolution is derived. The results are supported by a numerical particle simulation. Also the possibility of vortex excitation by ion bursts and coalescence of two vortexes are demonstrated. The effects of finite ion temperature, particle trapping and charge exchange collisions are discussed...

  20. Intra-cavity vortex beam generation

    CSIR Research Space (South Africa)

    Naidoo, Darryl

    2011-08-01

    Full Text Available In this paper the authors explore vortex beams and in particular the generation of single LG0l modes and superpositions thereof. Vortex beams carry orbital angular momentum (OAM) and this intrinsic property makes them prevalent in transferring...

  1. The bathtub vortex in a rotating container

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; Bohr, Tomas; Stenum, B.

    2006-01-01

    We study the time-independent free-surface flow which forms when a fluid drains out of a container, a so-called bathtub vortex. We focus on the bathtub vortex in a rotating container and describe the free-surface shape and the complex flow structure using photographs of the free surface, flow...

  2. Revealing the radial modes in vortex beams

    CSIR Research Space (South Africa)

    Sephton, Bereneice C

    2016-10-01

    Full Text Available Light beams that carry orbital angular momentum are often approximated by modulating an initial beam, usually Gaussian, with an azimuthal phase variation to create a vortex beam. Such vortex beams are well defined azimuthally, but the radial profile...

  3. Supersonic shock wave/vortex interaction

    Science.gov (United States)

    Settles, G. S.; Cattafesta, L.

    1993-01-01

    Although shock wave/vortex interaction is a basic and important fluid dynamics problem, very little research has been conducted on this topic. Therefore, a detailed experimental study of the interaction between a supersonic streamwise turbulent vortex and a shock wave was carried out at the Penn State Gas Dynamics Laboratory. A vortex is produced by replaceable swirl vanes located upstream of the throat of various converging-diverging nozzles. The supersonic vortex is then injected into either a coflowing supersonic stream or ambient air. The structure of the isolated vortex is investigated in a supersonic wind tunnel using miniature, fast-response, five-hole and total temperature probes and in a free jet using laser Doppler velocimetry. The cases tested have unit Reynolds numbers in excess of 25 million per meter, axial Mach numbers ranging from 2.5 to 4.0, and peak tangential Mach numbers from 0 (i.e., a pure jet) to about 0.7. The results show that the typical supersonic wake-like vortex consists of a non-isentropic, rotational core, where the reduced circulation distribution is self similar, and an outer isentropic, irrotational region. The vortex core is also a region of significant turbulent fluctuations. Radial profiles of turbulent kinetic energy and axial-tangential Reynolds stress are presented. The interactions between the vortex and both oblique and normal shock waves are investigated using nonintrusive optical diagnostics (i.e. schlieren, planar laser scattering, and laser Doppler velocimetry). Of the various types, two Mach 2.5 overexpanded-nozzle Mach disc interactions are examined in detail. Below a certain vortex strength, a 'weak' interaction exists in which the normal shock is perturbed locally into an unsteady 'bubble' shock near the vortex axis, but vortex breakdown (i.e., a stagnation point) does not occur. For stronger vortices, a random unsteady 'strong' interaction results that causes vortex breakdown. The vortex core reforms downstream of

  4. Traversing field of view and AR-PIV for mid-field wake vortex investigation in a towing tank

    Science.gov (United States)

    Scarano, F.; van Wijk, C.; Veldhuis, L. L. M.

    2002-08-01

    Wake vortex flow experiments are performed in a water tank where a 1:48 scaled model of a large transport aircraft A340-300 is towed at the speed of 3 and 5 ms-1 with values of the angle of attack α={2°, 4°, 8°}. Particle image velocimetry (PIV) measurements are performed in a plane perpendicular to the towing direction describing the streamwise component of the wake vorticity. The instantaneous field of view (I-FOV) is traversed vertically with an underwater moving-camera device tracking the vortex core during the downward motion. An adaptive resolution (AR) image-processing technique is introduced that enhances the PIV interrogation in terms of spatial resolution and accuracy. The main objectives of the investigation are to demonstrate the applicability of PIV diagnostics in wake vortex research with towing-tank facilities. The specific implementation of the traversing field-of-view (T-FOV) technique and the AR image processing are driven by the need to characterize the vortex wake global properties as well as the vortex decay phenomenon in the mid- and far-field. Relevant aerodynamic information is obtained in the mid-field where the time evolution of the vortex structure (core radius and tangential velocity) and of the overall vortex wake (vortex trajectory, descent velocity, circulation) are discussed.

  5. Bifurcation and instability problems in vortex wakes

    DEFF Research Database (Denmark)

    Aref, Hassan; Brøns, Morten; Stremler, Mark A.

    2007-01-01

    A number of instability and bifurcation problems related to the dynamics of vortex wake flows are addressed using various analytical tools and approaches. We discuss the bifurcations of the streamline pattern behind a bluff body as a vortex wake is produced, a theory of the universal Strouhal......-Reynolds number relation for vortex wakes, the bifurcation diagram for "exotic" wake patterns behind an oscillating cylinder first determined experimentally by Williamson & Roshko, and the bifurcations in topology of the streamlines pattern in point vortex streets. The Hamiltonian dynamics of point vortices...... in a periodic strip is considered. The classical results of von Kármán concerning the structure of the vortex street follow from the two-vortices-in-a-strip problem, while the stability results follow largely from a four-vortices-in-a-strip analysis. The three-vortices-in-a-strip problem is argued...

  6. Numerical Simulation of the Aircraft Wake Vortex Flowfield

    Science.gov (United States)

    Ahmad, Nashat N.; Proctor, Fred H.; Perry, R. Brad

    2013-01-01

    The near wake vortex flowfield from a NACA0012 half-wing was simulated using a fully unstructured Navier-Stokes flow solver in three dimensions at a chord Reynolds number of 4.6 million and a Mach number of approximately 0.15. Several simulations were performed to examine the effect of boundary conditions, mesh resolution and turbulence scheme on the formation of wingtip vortex and its downstream propagation. The standard Spalart-Allmaras turbulence model was compared with the Dacles-Mariani and Spalart-Shur corrections for rotation and curvature effects. The simulation results were evaluated using the data from experiment performed at NASA Ames' 32in x 48in low speed wind tunnel.

  7. Combustion of hydrogen in an experimental trapped vortex combustor

    Science.gov (United States)

    Wu, Hui; Chen, Qin; Shao, Weiwei; Zhang, Yongliang; Wang, Yue; Xiao, Yunhan

    2009-09-01

    Combustion performances of pure hydrogen in an experimental trapped vortex combustor have been tested under different operating conditions. Pressure fluctuations, NOx emissions, OH distributions, and LBO (Lean Blow Out) were measured in the tests. Results indicate that the TVC test rig has successfully realized a double vortex construction in the cavity zone in a wide range of flow conditions. Hydrogen combustion in the test rig has achieved an excellent LBO performance and relatively low NOx emissions. Through comparison of dynamic pressure data, OH fluctuation images, and NOx emissions, the optimal operating condition has been found out to be Φp =0.4, fuel split =0.4, and primary air/fuel premixed.

  8. Getting performance metrics right: a qualitative study of staff experiences implementing and measuring practice transformation.

    Science.gov (United States)

    Kansagara, Devan; Tuepker, Anaïs; Joos, Sandy; Nicolaidis, Christina; Skaperdas, Eleni; Hickam, David

    2014-07-01

    Quality improvement is a central goal of the patient-centered medical home (PCMH) model, and requires the use of relevant performance measures that can effectively guide comprehensive care improvements. Existing literature suggests performance measurement can lead to improvements in care quality, but may also promote practices that are detrimental to patient care. Staff perceptions of performance metric implementation have not been well-researched in medical home settings. To describe primary care staff (clinicians and other staff) experiences with the use of performance metrics during the implementation of the Veterans Health Administration's (VHA) Patient Aligned Care Team (PACT) model of care. Observational qualitative study; data collection using role-stratified focus groups and semi-structured interviews. Two hundred and forty-one of 337 (72 %) identified primary care clinic staff in PACT team and clinic administrative/other roles, from 15 VHA clinics in Oregon and Washington. Data coded and analyzed using conventional content analysis techniques. Primary care staff perceived that performance metrics: 1) led to delivery changes that were not always aligned with PACT principles, 2) did not accurately reflect patient-priorities, 3) represented an opportunity cost, 4) were imposed with little communication or transparency, and 5) were not well-adapted to team-based care. Primary care staff perceived responding to performance metrics as time-consuming and not consistently aligned with PACT principles of care. The gaps between the theory and reality of performance metric implementation highlighted by PACT team members are important to consider as the medical home model is more widely implemented.

  9. Altered left ventricular vortex ring formation by 4-dimensional flow magnetic resonance imaging after repair of atrioventricular septal defects.

    Science.gov (United States)

    Calkoen, Emmeline E; Elbaz, Mohammed S M; Westenberg, Jos J M; Kroft, Lucia J M; Hazekamp, Mark G; Roest, Arno A W; van der Geest, Rob J

    2015-11-01

    During normal left ventricular (LV) filling, a vortex ring structure is formed distal to the left atrioventricular valve (LAVV). Vortex structures contribute to efficient flow organization. We aimed to investigate whether LAVV abnormality in patients with a corrected atrioventricular septal defect (AVSD) has an impact on vortex ring formation. Whole-heart 4D flow MRI was performed in 32 patients (age: 26 ± 12 years), and 30 healthy subjects (age: 25 ± 14 years). Vortex ring cores were detected at peak early (E-peak) and peak late filling (A-peak). When present, the 3-dimensional position and orientation of the vortex ring was defined, and the circularity index was calculated. Through-plane flow over the LAVV, and the vortex formation time (VFT), were quantified to analyze the relationship of vortex flow with the inflow jet. Absence of a vortex ring during E-peak (healthy subjects 0%, vs patients 19%; P = .015), and A-peak (healthy subjects 10% vs patients 44%; P = .008) was more frequent in patients. In 4 patients, this was accompanied by a high VFT (5.1-7.8 vs 2.4 ± 0.6 in healthy subjects), and in another 2 patients with abnormal valve anatomy. In patients compared with controls, the vortex cores had a more-anterior and apical position, closer to the ventricular wall, with a more-elliptical shape and oblique orientation. The shape of the vortex core closely resembled the valve shape, and its orientation was related to the LV inflow direction. This study quantitatively shows the influence of abnormal LAVV and LV inflow on 3D vortex ring formation during LV inflow in patients with corrected AVSD, compared with healthy subjects. Copyright © 2015. Published by Elsevier Inc.

  10. Polynomial Apodizers for Centrally Obscured Vortex Coronagraphs

    Science.gov (United States)

    Fogarty, Kevin; Pueyo, Laurent; Mazoyer, Johan; N'Diaye, Mamadou

    2017-12-01

    Several coronagraph designs have been proposed over the last two decades to directly image exoplanets. Among these designs, vector vortex coronagraphs provide theoretically perfect starlight cancellation along with small inner working angles when deployed on telescopes with unobstructed pupils. However, current and planned space missions and ground-based extremely large telescopes present complex pupil geometries, including large central obscurations caused by secondary mirrors, which prevent vortex coronagraphs from rejecting on-axis sources entirely. Recent solutions combining the vortex phase mask with a ring-apodized pupil have been proposed to circumvent this issue, but provide a limited throughput for vortex charges > 2. We present pupil plane apodizations for charge 2, 4, and 6 vector vortex coronagraphs that compensate for pupil geometries with circularly symmetric central obstructions caused by on-axis secondary mirrors. These apodizations are derived analytically and allow vortex coronagraphs to retain theoretically perfect nulling in the presence of obstructed pupils. For a charge 4 vortex, we design polynomial apodization functions assuming a grayscale apodizing filter that represent a substantial gain in throughput over the ring-apodized vortex coronagraph design, while for a charge 6 vortex, we design polynomial apodized vortex coronagraphs that have ≳ 70 % total energy throughput for the entire range of central obscuration sizes studied. We propose methods for optimizing apodizations produced with either grayscale apodizing filters or shaped mirrors. We conclude by demonstrating how this design may be combined with apodizations numerically optimized for struts and primary mirror segment gaps to design terrestrial exoplanet imagers for complex pupils.

  11. Experimental benchmark and code validation for airfoils equipped with passive vortex generators

    Science.gov (United States)

    Baldacchino, D.; Manolesos, M.; Ferreira, C.; González Salcedo, Á.; Aparicio, M.; Chaviaropoulos, T.; Diakakis, K.; Florentie, L.; García, N. R.; Papadakis, G.; Sørensen, N. N.; Timmer, N.; Troldborg, N.; Voutsinas, S.; van Zuijlen, A.

    2016-09-01

    Experimental results and complimentary computations for airfoils with vortex generators are compared in this paper, as part of an effort within the AVATAR project to develop tools for wind turbine blade control devices. Measurements from two airfoils equipped with passive vortex generators, a 30% thick DU97W300 and an 18% thick NTUA T18 have been used for benchmarking several simulation tools. These tools span low-to-high complexity, ranging from engineering-level integral boundary layer tools to fully-resolved computational fluid dynamics codes. Results indicate that with appropriate calibration, engineering-type tools can capture the effects of vortex generators and outperform more complex tools. Fully resolved CFD comes at a much higher computational cost and does not necessarily capture the increased lift due to the VGs. However, in lieu of the limited experimental data available for calibration, high fidelity tools are still required for assessing the effect of vortex generators on airfoil performance.

  12. Analytical study on the SGS force around an elliptic Burgers vortex

    Science.gov (United States)

    Kobayashi, Hiromichi

    2016-11-01

    The subgrid-scale (SGS) force around an elliptic Burgers vortex is analytically examined. In turbulence, there are a lot of vortex-tubes whose cross sections are known to be approximated as the ellipse. In this study, the biaxial elliptic Burgers vortex is produced by adding the compressive and extensional background straining flow to the conventional Burgers vortex. By using a filtering operation, we revealed that the energy transfer by the Reynolds stress term applying the Bardina model exhibits negative correlation to that by the true SGS stress term. However, it has been recently reported that a combination of the Bardina Reynolds term and the eddy viscosity model gives good performance even for the coarse LES of turbulent channel flows. In order to understand that, we discuss some SGS forces: by the true SGS stress tensor, by the eddy viscosity model, by the modified Leonard term and by the Bardina Reynolds term. This work was supported by JSPS KAKENHI Grant Number 26420122.

  13. An experimental investigation of vortex stability, tip shapes, compressibility, and noise for hovering model rotors

    Science.gov (United States)

    Tangler, J. L.; Wohlfeld, R. M.; Miley, S. J.

    1973-01-01

    Schlieren methods of flow visualization and hot-wire anemometry for velocity measurements were used to investigate the wakes generated by hovering model propellers and rotors. The research program was directed toward investigating (1) the stability of the tip vortex, (2) the effects produced by various tip shapes on performance and tip vortex characteristics, and (3) the shock formation and noise characteristics associated with various tip shapes. A free-wake analysis was also conducted for comparison with the vortex stability experimental results. Schlieren photographs showing wake asymmetry, interaction, and instability are presented along with a discussion of the effects produced by the number of blades, collective pitch, and tip speed. Two hot-wire anemometer techniques, used to measure the maximum circumferential velocity in the tip vortex, are discussed.

  14. In-situ tunable vortex pinning with an array of ferromagnetic anti-dots

    Science.gov (United States)

    Wang, Yong-Lei; Xiao, Zhili; Ocola, Leo; Divan, Ralu; Crabtree, George W.; Kwok, Wai-Kwong; Superconductivity and Magnetism Group, MSD, Argonne National Lab Team

    2014-03-01

    We investigated vortex pinning effects of a ferromagnetic antidot array in a superconducting film. A square antidot array of 30 nm thick permalloy (Py) was patterned onto a MoGe superconducting film with thickness of 100 nm. Although we found no evidence of vortex pinning enhancement by the pristine magnetic antidot array in perpendicular magnetic fields, we found that by applying an independently controlled in-plane magnetic field the magnetic antidot array can provide excellent vortex pinning, resulting in a tunable superconducting critical current enhancement. Through micromagnetic simulation and magnetic force microscopy imaging, we demonstrate that the tunable vortex pinning originates from spatially periodic stray field generated by the magnetic antidot array in the presence of an in-plane magnetic field. This work was supported by DOE BES under Contract No. DE-AC02-06CH11357 that also funds Argonne's Center for Nanoscale Materials (CNM) where the nanopatterning was performed.

  15. A free wake vortex lattice model for vertical axis wind turbines: Modeling, verification and validation

    Science.gov (United States)

    Meng, Fanzhong; Schwarze, Holger; Vorpahl, Fabian; Strobel, Michael

    2014-12-01

    Since the 1970s several research activities had been carried out on developing aerodynamic models for Vertical Axis Wind Turbines (VAWTs). In order to design large VAWTs of MW scale, more accurate aerodynamic calculation is required to predict their aero-elastic behaviours. In this paper, a 3D free wake vortex lattice model for VAWTs is developed, verified and validated. Comparisons to the experimental results show that the 3D free wake vortex lattice model developed is capable of making an accurate prediction of the general performance and the instantaneous aerodynamic forces on the blades. The comparison between momentum method and the vortex lattice model shows that free wake vortex models are needed for detailed loads calculation and for calculating highly loaded rotors.

  16. Terahertz circular Airy vortex beams.

    Science.gov (United States)

    Liu, Changming; Liu, Jinsong; Niu, Liting; Wei, Xuli; Wang, Kejia; Yang, Zhengang

    2017-06-20

    Vortex beams have received considerable research interests both in optical and millimeter-wave domain since its potential to be utilized in the wireless communications and novel imaging systems. Many well-known optical beams have been demonstrated to carry orbital angular momentum (OAM), such as Laguerre-Gaussian beams and high-order Bessel beams. Recently, the radially symmetric Airy beams that exhibit an abruptly autofocusing feature are also demonstrated to be capable of carrying OAM in the optical domain. However, due to the lack of efficient devices to manipulate terahertz (THz) beams, it could be a challenge to demonstrate the radially symmetric Airy beams in the THz domain. Here we demonstrate the THz circular Airy vortex beams (CAVBs) with a 0.3-THz continuous wave through 3D printing technology. Assisted by the rapidly 3D-printed phase plates, individual OAM states with topological charge l ranging from l = 0 to l = 3 and a multiplexed OAM state are successfully imposed into the radially symmetric Airy beams. We both numerically and experimentally investigate the propagation dynamics of the generated THz CAVBs, and the simulations agree well with the observations.

  17. Introduction to Vortex Lattice Theory

    Directory of Open Access Journals (Sweden)

    Santiago Pinzón

    2015-10-01

    Full Text Available Panel methods have been widely used in industry and are well established since the 1970s for aerodynamic analysis and computation. The Vortex Lattice Panel Method presented in this study comes across a sophisticated method that provides a quick solution time, allows rapid changes in geometry and suits well for aerodynamic analysis. The aerospace industry is highly competitive in design efficiency, and perhaps one of the most important factors on airplane design and engineering today is multidisciplinary optimization.  Any cost reduction method in the design cycle of a product becomes vital in the success of its outcome. The subsequent sections of this article will further explain in depth the theory behind the vortex lattice method, and the reason behind its selection as the method for aerodynamic analysis during preliminary design work and computation within the aerospace industry. This article is analytic in nature, and its main objective is to present a mathematical summary of this widely used computational method in aerodynamics.

  18. Investigating the performances of a 1 MV high pulsed power linear transformer driver: from beam dynamics to x radiation

    Science.gov (United States)

    Maisonny, R.; Ribière, M.; Toury, M.; Plewa, J. M.; Caron, M.; Auriel, G.; d'Almeida, T.

    2016-12-01

    The performance of a 1 MV pulsed high-power linear transformer driver accelerator were extensively investigated based on a numerical approach which utilizes both electromagnetic and Monte Carlo simulations. Particle-in-cell calculations were employed to examine the beam dynamics throughout the magnetically insulated transmission line which governs the coupling between the generator and the electron diode. Based on the information provided by the study of the beam dynamics, and using Monte Carlo methods, the main properties of the resulting x radiation were predicted. Good agreement was found between these simulations and experimental results. This work provides a detailed understanding of mechanisms affecting the performances of this type of high current, high-voltage pulsed accelerator, which are very promising for a growing number of applications.

  19. PREFACE: Special section on vortex rings Special section on vortex rings

    Science.gov (United States)

    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

  20. Enhancing Public Sector Performance : Malaysia’s Experience with Transforming Land Administration

    OpenAIRE

    World Bank Group

    2017-01-01

    This report is part of the series focusing on documenting the lessons from Malaysia for other developing countries in improving their public-sector management. These lessons include those at the center of government, such as the delivery unit method applied to the implementation of the national priorities, or implementing the elements of performance-based budgeting, as well as deeper analy...

  1. Generation of hollow beam with radially polarized vortex beam and complex amplitude filter.

    Science.gov (United States)

    Lin, Jie; Chen, Ran; Yu, Haichao; Jin, Peng; Ma, Yuan; Cada, Michael

    2014-07-01

    The generation of hollow beams with a long focal depth from a radially polarized Bessel-Gaussian beam with a second-order vortex phase and an amplitude filter is theoretically investigated by Richards-Wolf's integral. The null intensity on the optical axis is achieved by introducing the second-order vortex. The long focal depth is a result of the amplitude filtering based on the cosine function and Euler transformation. Numerical results indicate that the focal depth of a hollow beam is improved from 0.96λ to 2.28λ with a slight increase of the transverse size for the simplest amplitude filter design. The intensity distribution twist phenomenon of the x- and y-polarized components around the optical axis due to the introducing of the vortex phase is also discussed. It is believed that the proposed scheme can be used to achieve particle acceleration and optical trapping.

  2. Generation of cylindrically polarized vector vortex beams with digital micromirror device

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Lei; Liu, Weiwei; Wang, Meng; Zhong, Mincheng; Wang, Ziqiang; Li, Yinmei, E-mail: liyinmei@ustc.edu.cn [Department of Optics and Optical Engineering, University of Science and Technology of China, Hefei, Anhui Province 230026 (China); Ren, Yuxuan [National Center for Protein Sciences Shanghai, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, CAS, Shanghai 201210 (China)

    2014-11-14

    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 the way for optical microscopy, trapping, and communication.

  3. Fluid entrainment by isolated vortex rings

    Science.gov (United States)

    Dabiri, John O.; Gharib, Morteza

    2004-07-01

    Of particular importance to the development of models for isolated vortex ring dynamics in a real fluid is knowledge of ambient fluid entrainment by the ring. This time-dependent process dictates changes in the volume of fluid that must share impulse delivered by the vortex ring generator. Therefore fluid entrainment is also of immediate significance to the unsteady forces that arise due to the presence of vortex rings in starting flows. Applications ranging from industrial and transportation, to animal locomotion and cardiac flows, are currently being investigated to understand the dynamical role of the observed vortex ring structures. Despite this growing interest, fully empirical measurements of fluid entrainment by isolated vortex rings have remained elusive. The primary difficulties arise in defining the unsteady boundary of the ring, as well as an inability to maintain the vortex ring in the test section sufficiently long to facilitate measurements. We present a new technique for entrainment measurement that utilizes a coaxial counter-flow to retard translation of vortex rings generated from a piston cylinder apparatus, so that their growth due to fluid entrainment can be observed. Instantaneous streamlines of the flow are used to determine the unsteady vortex ring boundary and compute ambient fluid entrainment. Measurements indicate that the entrainment process does not promote self-similar vortex ring growth, but instead consists of a rapid convection-based entrainment phase during ring formation, followed by a slower diffusive mechanism that entrains ambient fluid into the isolated vortex ring. Entrained fluid typically constitutes 30% to 40% of the total volume of fluid carried with the vortex ring. Various counter-flow protocols were used to substantially manipulate the diffusive entrainment process, producing rings with entrained fluid fractions up to 65%. Measurements of vortex ring growth rate and vorticity distribution during diffusive entrainment

  4. Depletion of ozone and reservoir species of chlorine and nitrogen oxide in the lower Antarctic polar vortex measured from aircraft

    Science.gov (United States)

    Jurkat, T.; Voigt, C.; Kaufmann, S.; Grooß, J.-U.; Ziereis, H.; Dörnbrack, A.; Hoor, P.; Bozem, H.; Engel, A.; Bönisch, H.; Keber, T.; Hüneke, T.; Pfeilsticker, K.; Zahn, A.; Walker, K. A.; Boone, C. D.; Bernath, P. F.; Schlager, H.

    2017-06-01

    Novel airborne in situ measurements of inorganic chlorine, nitrogen oxide species, and ozone were performed inside the lower Antarctic polar vortex and at its edge in September 2012. We focus on one flight during the Transport and Composition of the LMS/Earth System Model Validation (TACTS/ESMVal) campaign with the German research aircraft HALO (High-Altitude LOng range research aircraft), reaching latitudes of 65°S and potential temperatures up to 405 K. Using the early winter correlations of reactive trace gases with N2O from the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), we find high depletion of chlorine reservoir gases up to ˜40% (0.8 ppbv) at 12 km to 14 km altitude in the vortex and 0.4 ppbv at the edge in subsided stratospheric air with mean ages up to 4.5 years. We observe denitrification of up to 4 ppbv, while ozone was depleted by 1.2 ppmv at potential temperatures as low as 380 K. The advanced instrumentation aboard HALO enables high-resolution measurements with implications for the oxidation capacity of the lowermost stratosphere.

  5. Comparative Investigation on the Performance of Modified System Poles and Traditional System Poles Obtained from PDC Data for Diagnosing the Ageing Condition of Transformer Polymer Insulation Materials

    Directory of Open Access Journals (Sweden)

    Jiefeng Liu

    2018-02-01

    Full Text Available The life expectancy of a transformer is largely depended on the service life of transformer polymer insulation materials. Nowadays, several papers have reported that the traditional system poles obtained from polarization and depolarization current (PDC data can be used to assess the condition of transformer insulation systems. However, the traditional system poles technique only provides limited ageing information for transformer polymer insulation. In this paper, the modified system poles obtained from PDC data are proposed to assess the ageing condition of transformer polymer insulation. The aim of the work is to focus on reporting a comparative investigation on the performance of modified system poles and traditional system poles for assessing the ageing condition of a transformer polymer insulation system. In the present work, a series of experiments have been performed under controlled laboratory conditions. The PDC measurement data, degree of polymerization (DP and moisture content of the oil-immersed polymer pressboard specimens were carefully monitored. It is observed that, compared to the relationships between traditional system poles and DP values, there are better correlations between the modified system poles and DP values, because the modified system poles can obtain much more ageing information on transformer polymer insulation. Therefore, the modified system poles proposed in the paper are more suitable for the diagnosis of the ageing condition of transformer polymer insulation.

  6. A novel vortex tube-based N2-expander liquefaction process for enhancing the energy efficiency of natural gas liquefaction

    Directory of Open Access Journals (Sweden)

    Qyyum Muhammad Abdul

    2017-01-01

    Full Text Available This research work unfolds a simple, safe, and environment-friendly energy efficient novel vortex tube-based natural gas liquefaction process (LNG. A vortex tube was introduced to the popular N2-expander liquefaction process to enhance the liquefaction efficiency. The process structure and condition were modified and optimized to take a potential advantage of the vortex tube on the natural gas liquefaction cycle. Two commercial simulators ANSYS® and Aspen HYSYS® were used to investigate the application of vortex tube in the refrigeration cycle of LNG process. The Computational fluid dynamics (CFD model was used to simulate the vortex tube with nitrogen (N2 as a working fluid. Subsequently, the results of the CFD model were embedded in the Aspen HYSYS® to validate the proposed LNG liquefaction process. The proposed natural gas liquefaction process was optimized using the knowledge-based optimization (KBO approach. The overall energy consumption was chosen as an objective function for optimization. The performance of the proposed liquefaction process was compared with the conventional N2-expander liquefaction process. The vortex tube-based LNG process showed a significant improvement of energy efficiency by 20% in comparison with the conventional N2-expander liquefaction process. This high energy efficiency was mainly due to the isentropic expansion of the vortex tube. It turned out that the high energy efficiency of vortex tube-based process is totally dependent on the refrigerant cold fraction, operating conditions as well as refrigerant cycle configurations.

  7. A novel vortex tube-based N2-expander liquefaction process for enhancing the energy efficiency of natural gas liquefaction

    Science.gov (United States)

    Qyyum, Muhammad Abdul; Wei, Feng; Hussain, Arif; Ali, Wahid; Sehee, Oh; Lee, Moonyong

    2017-11-01

    This research work unfolds a simple, safe, and environment-friendly energy efficient novel vortex tube-based natural gas liquefaction process (LNG). A vortex tube was introduced to the popular N2-expander liquefaction process to enhance the liquefaction efficiency. The process structure and condition were modified and optimized to take a potential advantage of the vortex tube on the natural gas liquefaction cycle. Two commercial simulators ANSYS® and Aspen HYSYS® were used to investigate the application of vortex tube in the refrigeration cycle of LNG process. The Computational fluid dynamics (CFD) model was used to simulate the vortex tube with nitrogen (N2) as a working fluid. Subsequently, the results of the CFD model were embedded in the Aspen HYSYS® to validate the proposed LNG liquefaction process. The proposed natural gas liquefaction process was optimized using the knowledge-based optimization (KBO) approach. The overall energy consumption was chosen as an objective function for optimization. The performance of the proposed liquefaction process was compared with the conventional N2-expander liquefaction process. The vortex tube-based LNG process showed a significant improvement of energy efficiency by 20% in comparison with the conventional N2-expander liquefaction process. This high energy efficiency was mainly due to the isentropic expansion of the vortex tube. It turned out that the high energy efficiency of vortex tube-based process is totally dependent on the refrigerant cold fraction, operating conditions as well as refrigerant cycle configurations.

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

    Science.gov (United States)

    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 BaTiO3 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 BaTiO3 nanoparticle.

  9. Interactivity And Mental Arithmetic: Coupling Mind And World Transforms And Enhances Performance

    Directory of Open Access Journals (Sweden)

    Guthrie Lisa G.

    2015-06-01

    Full Text Available Interactivity has been linked to better performance in problem solving, due in part to a more efficient allocation of attentional resources, a better distribution of cognitive load, but perhaps more important by enabling the reasoner to shape and reshape the physical problem presentation to promote the development of the problem solution. Interactivity in solving quotidian arithmetic problems involves gestures, pointing, and the recruitment of artefacts to facilitate computation and augment efficiency. In the experiment reported here, different types of interactivity were examined with a series of mental arithmetic problems. Using a repeated-measures design, participants solved series of five 11-digit sums in four conditions that varied in the type of interactivity: (i no interactivity (participants solved the problems with their hands on the table top, (ii pointing (participants could point at the numbers, (iii pen and paper (participants could note interim totals with a pen, and (iv tokens (the sums were presented as 11 numbered tokens the arrangement of which participants were free to modify as they proceeded to the solution. Performance in the four conditions was measured in terms of accuracy, calculation error, and efficiency (a ratio composed of the proportion correct over the proportion of time invested in working on the sums. These quantitative analyses were supplemented by a detailed qualitative examination of a participant’s actions in the different conditions. The integration of artefacts, such as tokens or a pen, offered reasoners the opportunity to reconfigure the physical presentation of the problem, enacting different arithmetic strategies: the affordance landscape shifts as the problem trajectory is enacted through interactivity, and this generally produced better “mental” arithmetic performance. Participants also felt more positive about and better engaged with the task when they could reconfigure the problem presentation

  10. Performance Characterization of the Air Force Transformational Satellite 12 kW Hall Thruster

    Science.gov (United States)

    Kamhawi, Hani; Haag, Thomas W.; Smith, Timothy; Herman, Daniel; Huang, Wensheng; Shastry, Rohit; Peterson, Peter; Mathers, Alex

    2013-01-01

    The STMD GCD ISP project is tasked with developing, maturing, and testing enabling human exploration propulsion requirements and potential designs for advanced high-energy, in-space propulsion systems to support deep-space human exploration and reduce travel time between Earth's orbit and future destinations for human activity. High-power Hall propulsion systems have been identified as enabling technologies and have been the focus of the activities at NASA Glenn-In-house effort to evaluate performance and interrogate operation of NASA designed and manufactured Hall thrusters. Evaluate existing high TRL EP devices that may be suitable for implementation in SEP TDM.

  11. A VORTEX MODEL OF A HELICOPTER ROTOR

    Directory of Open Access Journals (Sweden)

    Valentin BUTOESCU

    2009-06-01

    Full Text Available A vortex model of a helicopter rotor is presented. Each blade of the rotor has three degrees of freedom: flapping, lagging and feathering. The motions after each degree of freedom are also known for all blades. The blade is modelled as a thin vortex surface. The wakes are free fluid surfaces. A system of five equations are obtained: the first one is the integral equation of the lifting surface (rotor, the next three describe the wakes motion, and the last one relates the vortex strength on the wakes and the variation of vorticity on the rotor. A numerical solution of this system is presented. To avoid the singularities that can occur due to the complexity of vortex system, a desingularized model of the vortex core was adopted. A Mathcad worksheet containing the method has been written.The original contribution of the work. The calculation method of the motion of the wakes free vortex system, the development of the vortex cores in time and a new method to approximate the aerodynamic influence of remoted wake regions.

  12. Phase diagram of a lattice of pancake vortex molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Y., E-mail: y.tanaka@aist.go.j [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Crisan, A. [University of Birmingham, Birmingham (United Kingdom); National Institute of Materials Physics, Bucharest (Romania); Shivagan, D.D.; Iyo, A.; Shirage, P.M. [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Tokiwa, K.; Watanabe, T. [Tokyo University of Science, Noda (Japan); Terada, N. [Kagoshima University, Kagoshima (Japan)

    2009-10-15

    On a superconducting bi-layer with thickness much smaller than the penetration depth, lambda, a vortex molecule might form. A vortex molecule is composed of two fractional vortices and a soliton wall. The soliton wall can be regarded as a Josephson vortex missing magnetic flux (degenerate Josephson vortex) due to an incomplete shielding. The magnetic energy carried by fractional vortices is less than in the conventional vortex. This energy gain can pay a cost to form a degenerate Josephson vortex. The phase diagram of the vortex molecule is rich because of its rotational freedom.

  13. New scanning technique for the optical vortex microscope.

    Science.gov (United States)

    Augustyniak, Ireneusz; Popiołek-Masajada, Agnieszka; Masajada, Jan; Drobczyński, Sławomir

    2012-04-01

    In the optical vortex microscopy the focused Gaussian beam with optical vortex scans a sample. An optical vortex can be introduced into a laser beam with the use of a special optical element--a vortex lens. When moving the vortex lens, the optical vortex changes its position inside the spot formed by a focused laser beam. This effect can be used as a new precise scanning technique. In this paper, we study the optical vortex behavior at the sample plane. We also estimate if the new scanning technique results in observable effects that could be used for a phase object detection.

  14. A High-Performance Lossless Compression Scheme for EEG Signals Using Wavelet Transform and Neural Network Predictors

    Directory of Open Access Journals (Sweden)

    N. Sriraam

    2012-01-01

    Full Text Available Developments of new classes of efficient compression algorithms, software systems, and hardware for data intensive applications in today's digital health care systems provide timely and meaningful solutions in response to exponentially growing patient information data complexity and associated analysis requirements. Of the different 1D medical signals, electroencephalography (EEG data is of great importance to the neurologist for detecting brain-related disorders. The volume of digitized EEG data generated and preserved for future reference exceeds the capacity of recent developments in digital storage and communication media and hence there is a need for an efficient compression system. This paper presents a new and efficient high performance lossless EEG compression using wavelet transform and neural network predictors. The coefficients generated from the EEG signal by integer wavelet transform are used to train the neural network predictors. The error residues are further encoded using a combinational entropy encoder, Lempel-Ziv-arithmetic encoder. Also a new context-based error modeling is also investigated to improve the compression efficiency. A compression ratio of 2.99 (with compression efficiency of 67% is achieved with the proposed scheme with less encoding time thereby providing diagnostic reliability for lossless transmission as well as recovery of EEG signals for telemedicine applications.

  15. Experimental optimization of p-polarized MAIR spectrometry performed on a fourier transform infrared spectrometer.

    Science.gov (United States)

    Hasegawa, Takeshi; Itoh, Yuki; Kasuya, Akiyoshi

    2008-01-01

    Optimized experimental conditions of infrared p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) for the analysis of ultrathin films on glass have been explored. When the original MAIRS technique is employed for thin-film analysis on a substrate of germanium or silicon, which exhibits a high refractive index, an established experimental condition without optimization can be adapted for the measurements. On the other hand, the p-MAIRS technique that has been developed for analysis on a low-refractive-index material requires, however, optimization of the experimental parameters for a 'quantitative' molecular orientation analysis. The optimization cannot be performed by considering only for optics in the spectrometer, but for optics concerning the substrate should also be considered. In the present study, an optimized condition for infrared p-MAIRS analysis on glass has been revealed, which can be used for quantitative molecular orientation analysis in ultrathin films on glass.

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

    Science.gov (United States)

    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.

  17. On the Use of Vortex-Fitting in the Numerical Simulation of Blade-Vortex Interaction

    Science.gov (United States)

    Srinivasan, G. R.; VanDalsem, William (Technical Monitor)

    1997-01-01

    The usefulness of vortex-fitting in the computational fluid dynamics (CFD) methods to preserve the vortex strength and structure while convecting in a uniform free stream is demonstrated through the numerical simulations of two- and three-dimensional blade-vortex interactions. The fundamental premise of the formulation is the velocity and pressure field of the interacting vortex are unaltered either in the presence of an airfoil or a rotor blade or by the resulting nonlinear interactional flowfield. Although, the governing Euler and Navier-Stokes equations are nonlinear and independent solutions cannot be superposed, the interactional flowfield can be accurately captured by adding and subtracting the flowfield of the convecting vortex at each instant. The aerodynamics and aeroacoustics of two- and three-dimensional blade-vortex interactions have been calculated in Refs. 1-6 using this concept. Some of the results from these publications and similar other published material will be summarized in this paper.

  18. Dynamic Optimization for Vortex Shedding Suppression

    Directory of Open Access Journals (Sweden)

    Bonis Ioannis

    2016-01-01

    Full Text Available Flows around structures exhibiting vortex shedding induce vibrations that can potentially damage the structure. A way to avoid it is to suppress vortex shedding by controlling the wake. Wake control of laminar flow behind a rotating cylinder is formulated herein as a dynamic optimization problem. Angular cylinder speed is the manipulated variable that is adjusted to suppress vortex shedding by minimizing lift coefficient variation. The optimal angular speed is assumed to be periodic like wake formation. The control problem is solved for different time horizons tH. The impact of tH to control is evaluated and the need for feedback is assessed.

  19. Aircraft control in wake vortex wind shear

    Science.gov (United States)

    Wold, Gregory R.

    1995-01-01

    In the past, there have been a number of fatal incidents attributable to wake vortex encounters, involving both general aviation and commercial aircraft. In fact, the wake vortex hazard is considered to be the single dominant safety issue determining the aircraft spacing requirements at airports. As the amount of air traffic increases, the number of dangerous encounters is likely only to increase. It is therefore imperative that a means be found to reduce the danger. That is the purpose of this research: to use nonlinear inverse dynamic (NID) control methods in the design of an aircraft control system which can improve the safety margin in a wake vortex encounter.

  20. Acoustooptic operation of optical vortex beams

    Science.gov (United States)

    Martynyuk-Lototska, Iryna; Vasylkiv, Yurii; Dudok, Taras; Skab, Ihor; Vlokh, Rostyslav

    2018-02-01

    Using acoustooptic (AO) cells based on TeO2 crystal and silica glass, we have experimentally shown for the first time that the intensity profile and the phase structure of the vortex beam are preserved under AO Bragg diffraction. As a result, the vortex beam can be deflected due to AO diffraction, whereas the acoustooptically operated vortex beams can be efficiently used in such novel branches of optical technology as optical trapping and controlled addressing of the beams with different orbital angular momentums.

  1. Vortex motion behind a circular cylinder

    Science.gov (United States)

    Foeppl, L.

    1983-01-01

    Vortex motion behind a circular cylinder moving through water is discussed. It is shown that a pair of vortices form behind a moving cylinder and that their centers will move along a predictable curve. This curve represents an equilibrium condition which, however, is subject to perturbation. The stability of the vortex pair is investigated. Movement of the vortex pair away from the cylinder is calculated as an explanation of the resistance of the cylinder. Finally, the principles elaborated are applied to the flow around a flat plate.

  2. Electron vortex beams in a magnetic field and spin filter

    OpenAIRE

    Chowdhury, Debashree; Basu, Banasri; Bandyopadhyay, Pratul

    2015-01-01

    We investigate the propagation of electron vortex beams in a magnetic field. It is pointed out that when electron vortex beams carrying orbital angular momentum propagate in a magnetic field, the Berry curvature associated with the scalar electron moving in a cyclic path around the vortex line is modified from that in free space. This alters the spin-orbit interaction, which affects the propagation of nonparaxial beams. The electron vortex beams with tilted vortex lead to spin Hall effect in ...

  3. Secondary vortex formation in ring vortices in free jets

    Science.gov (United States)

    Schneider, E. M.

    1980-10-01

    Secondary vortex formation is examined as a basic component of the turbulent condition of vortex and laminar currents. Dyed fluid ring vortices are used to investigate formation moving against an object and in an unobstructed environment. Part of the vortex structure of jets can be explained by means of secondary vortices, and the sound spectrum both of a single turbulent vortex and of jets is influenced by secondary vortex formation.

  4. Vortex disruption by magnetohydrodynamic feedback

    CERN Document Server

    Mak, Julian; Hughes, D W

    2016-01-01

    In an electrically conducting fluid, vortices stretch out a weak, large-scale magnetic field to form strong current sheets on their edges. Associated with these current sheets are magnetic stresses, which are subsequently released through reconnection, leading to vortex disruption, and possibly even destruction. This disruption phenomenon is investigated here in the context of two-dimensional, homogeneous, incompressible magnetohydrodynamics. We derive a simple order of magnitude estimate for the magnetic stresses --- and thus the degree of disruption --- that depends on the strength of the background magnetic field (measured by the parameter $M$, a ratio between the Alfv\\'en speed and a typical flow speed) and on the magnetic diffusivity (measured by the magnetic Reynolds number $\\mbox{Rm}$). The resulting estimate suggests that significant disruption occurs when $M^{2}\\mbox{Rm} = O(1)$. To test our prediction, we analyse direct numerical simulations of vortices generated by the breakup of unstable shear flo...

  5. Water tunnel results of leading-edge vortex flap tests on a delta wing vehicle

    Science.gov (United States)

    Delfrate, J. H.

    1986-01-01

    A water tunnel flow visualization test on leading edge vortex flaps was conducted at the flow visualization facility of the NASA Ames Research Center's Dryden Flight Research Facility. The purpose of the test was to visually examine the vortex structures caused by various leading edge vortex flaps on the delta wing of an F-106 model. The vortex flaps tested were designed analytically and empirically at the NASA Langley Research Center. The three flap designs were designated as full-span gothic flap, full-span untapered flap, and part-span flap. The test was conducted at a Reynolds number of 76,000/m (25,000/ft). This low Reynolds number was used because of the 0.076-m/s (0.25-ft/s) test section flow speed necessary for high quality flow visualization. However, this low Reynolds number may have influenced the results. Of the three vortex flaps tested, the part-span flap produced what appeared to be the strongest vortex structure over the flap area. The full-span gothic flap provided the next best performance.

  6. Mechanisms for the symmetric and antisymmetric switching of a magnetic vortex core: Differences and common aspects

    Science.gov (United States)

    Noske, Matthias; Stoll, Hermann; Fähnle, Manfred; Hertel, Riccardo; Schütz, Gisela

    2015-01-01

    Three-dimensional micromagnetic simulations of the switching of a magnetic vortex core in a cylindrical nanodisk are performed, for excitations with out-of-plane fields (symmetric switching) or with various types of time-dependent in-plane fields (asymmetric switching). Although the switching mechanisms are different in detail, all switching events must involve the movement of a Bloch point through the disk, because the switching leads to a change of the Skyrmion number which is a topological invariant as long as there is no action of a Bloch point. The momentary magnetization configurations are different in different layers of the disk. Because of the three-dimensionality it is often difficult to decide whether the asymmetric switching is caused by the splitting of the dip close to the vortex core into a vortex-antivortex pair, and the annihilation of the original vortex with the antivortex (whereby a Bloch point moves). It is suggested that there are situations for which such a switching occurs by the formation of a Bloch point in a configuration which is already similar to a vortex-antivortex configuration, but by a movement of this Bloch point before the formation of a complete pair and without the annihilation of the original vortex with an antivortex.

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

    Science.gov (United States)

    1990-12-01

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

  8. Drift due to viscous vortex rings

    Science.gov (United States)

    Morrell, Thomas; Spagnolie, Saverio; Thiffeault, Jean-Luc

    2016-11-01

    Biomixing is the study of fluid mixing due to swimming organisms. While large organisms typically produce turbulent flows in their wake, small organisms produce less turbulent wakes; the main mechanism of mixing is the induced net particle displacement (drift). Several experiments have examined this drift for small jellyfish, which produce vortex rings that trap and transport a fair amount of fluid. Inviscid theory implies infinite particle displacements for the trapped fluid, so the effect of viscosity must be included to understand the damping of real vortex motion. We use a model viscous vortex ring to compute particle displacements and other relevant quantities, such as the integrated moments of the displacement. Fluid entrainment at the tail end of a growing vortex 'envelope' is found to play an important role in the total fluid transport and drift. Partially supported by NSF Grant DMS-1109315.

  9. Vortex Shedding From a Flexible Hydrofoil

    CERN Document Server

    Dreyer, Matthieu

    2011-01-01

    Video of vortex shedding in the wake of a Naca0009 hydrofoil made of polyoxymethylene type C (POM C). This video was submitted as part of the Gallery of Fluid Motion 2011 which is showcase of fluid dynamics videos.

  10. Vortex structure and characterization of quasiperiodic functions

    CERN Document Server

    Dana, I

    2002-01-01

    Quasiperiodic functions (QPFs) are characterized by their full vortex structure in one unit cell. This characterization is much finer and more sensitive than the topological one given by the total vorticity per unit cell (the 'Chern index'). It is shown that QPFs with an arbitrarily prescribed vortex structure exist by constructing explicitly such a 'standard' QPF. Two QPFs with the same vortex structure are equivalent, in the sense that their ratio is a function which is strictly periodic, nonvanishing and at least continuous. A general QPF can then be approximately reconstructed from its vortex structure on the basis of the standard QPF and the equivalence concept. As another application of this concept, a simple method is proposed for calculating the quasiperiodic eigenvectors of periodic matrices. Possible applications to the quantum-chaos problem on a phase-space torus are briefly discussed.

  11. Development of gas pressure vortex regulator

    Science.gov (United States)

    Uss, A. Yu.; Chernyshyov, A. V.; Krylov, V. I.

    2017-08-01

    The present paper describes the applications of vortex regulators and the current state of the issue on the use and development of such devices. A patent review has been carried out. Automatic control systems using a vortex regulator are considered. Based on the analysis and preliminary numerical calculation of gas flow in the working cavity of the regulator, a new design of a vortex gas pressure regulator has been developed. An experimental sample of the device was made using additive technologies and a number of tests were carried out. The results of experimental studies confirmed the adequacy of the created mathematical model. Based on further numerical studies a new design of a vortex regulator with a distributed feed of the process control flow as well as with the regulated swirl of the supply and control process flows has been developed.

  12. Advanced Vortex Hybrid Rocket Engine (AVHRE) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ORBITEC proposes to develop a unique Advanced Vortex Hybrid Rocket Engine (AVHRE) to achieve a safe, highly-reliable, low-cost and uniquely versatile propulsion...

  13. Advanced Vortex Hybrid Rocket Engine (AVHRE) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Orbital Technologies Corporation (ORBITEC) proposes to develop a unique Advanced Vortex Hybrid Rocket Engine (AVHRE) to achieve a highly-reliable, low-cost and...

  14. Numerical simulations of trailing vortex bursting

    Science.gov (United States)

    Beran, Philip S.

    1987-01-01

    Solutions of the steady-state Navier-Stokes equations for the axisymmetric bursting of a laminar trailing vortex are computed with Newton's method and the pseudo-arc length continuation method for wide ranges of vortex strength and Reynolds number. The results indicate that a trailing vortex can undergo a transition from a state in which the core slowly diffuses to a state marked by large amplitude, spatial oscillations of core radius and core axial velocity. At the transition point the core grows rapidly in size. This event is interpreted as vortex bursting. The results also suggest that when the maximum core swirl velocity is sufficiently large the centerline axial flow downstream of transition will be reversed.

  15. Cockpit-based Wake Vortex Visualization Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To prevent aircraft accidents due to wake vortex hazards, FAA procedures specify the minimum separation required between different categories of aircraft. However, a...

  16. Free wake models for vortex methods

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, K. [Technical Univ. Berlin, Aerospace Inst. (Germany)

    1997-08-01

    The blade element method works fast and good. For some problems (rotor shapes or flow conditions) it could be better to use vortex methods. Different methods for calculating a wake geometry will be presented. (au)

  17. Applications of 2D helical vortex dynamics

    DEFF Research Database (Denmark)

    Okulov, Valery; Sørensen, Jens Nørkær

    2010-01-01

    In the paper, we show how the assumption of helical symmetry in the context of 2D helical vortices can be exploited to analyse and to model various cases of rotating flows. From theory, examples of three basic applications of 2D dynamics of helical vortices embedded in flows with helical symmetry...... of the vorticity field are addressed. These included some of the problems related to vortex breakdown, instability of far wakes behind rotors and vortex theory of ideal rotors....

  18. Polynomial Apodizers for Centrally Obscured Vortex Coronagraphs

    OpenAIRE

    Fogarty, Kevin; Pueyo, Laurent; Mazoyer, Johan; N'Diaye, Mamadou

    2017-01-01

    Several coronagraph designs have been proposed over the last two decades to directly image exoplanets. Among these designs, the vector vortex coronagraphs provide theoretically perfect starlight cancellation along with small inner working angles when deployed on telescopes with unobstructed pupils. However, current and planned space missions and ground-based extremely large telescopes present complex pupil geometries, including secondary mirror central obscurations, that prevent vortex corona...

  19. Spatiotemporal complexity of the aortic sinus vortex

    Science.gov (United States)

    Moore, Brandon; Dasi, Lakshmi Prasad

    2014-07-01

    The aortic sinus vortex is a classical flow structure of significant importance to aortic valve dynamics and the initiation and progression of calcific aortic valve disease. We characterize the spatiotemporal characteristics of aortic sinus vortex dynamics in relation to the viscosity of blood analog solution as well as heart rate. High-resolution time-resolved (2 kHz) particle image velocimetry was conducted to capture 2D particle streak videos and 2D instantaneous velocity and streamlines along the sinus midplane using a physiological but rigid aorta model fitted with a porcine bioprosthetic heart valve. Blood analog fluids used include a water-glycerin mixture and saline to elucidate the sensitivity of vortex dynamics to viscosity. Experiments were conducted to record 10 heart beats for each combination of blood analog and heart rate condition. Results show that the topological characteristics of the velocity field vary in timescales as revealed using time bin-averaged vectors and corresponding instantaneous streamlines. There exist small timescale vortices and a large timescale main vortex. A key flow structure observed is the counter vortex at the upstream end of the sinus adjacent to the base (lower half) of the leaflet. The spatiotemporal complexity of vortex dynamics is shown to be profoundly influenced by strong leaflet flutter during systole with a peak frequency of 200 Hz and peak amplitude of 4 mm observed in the saline case. While fluid viscosity influences the length and timescales as well as the introduction of leaflet flutter, heart rate influences the formation of counter vortex at the upstream end of the sinus. Higher heart rates are shown to reduce the strength of the counter vortex that can greatly influence the directionality and strength of shear stresses along the base of the leaflet. This study demonstrates the impact of heart rate and blood analog viscosity on aortic sinus hemodynamics.

  20. CFD analysis of fin tube heat exchanger with a pair of delta winglet vortex generators

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Seong Won; Kim, Dong Hwan; Min, June Kee; Jeong, Ji Hwan [Pusan National Univ., Busan (Korea, Republic of)

    2012-09-15

    Among tubular heat exchangers, fin tube types are the most widely used in refrigeration and air-conditioning equipment. Efforts to enhance the performance of these heat exchangers included variations in the fin shape from a plain fin to a slit and louver type. In the context of heat transfer augmentation, the performance of vortex generators has also been investigated. Delta winglet vortex generators have recently attracted research interest, partly due to experimental data showing that their addition to fin-tube heat exchangers considerably reduces pressure loss at heat transfer capacity of nearly the same level. The efficiency of the delta winglet vortex generators widely varies depending on their size and shape, as well as the locations where they are implemented. In this paper, the flow field around delta winglet vortex generators in a common flow up arrangement was analyzed in terms of flow characteristics and heat transfer using computational fluid dynamics methods. Flow mixing due to vortices and delayed separation due to acceleration influence the overall fin performance. The fin with delta winglet vortex generators exhibited a pressure loss lower than that of a plain fin, and the heat transfer performance was enhanced at high air velocity or Reynolds number.

  1. Experimental investigation of vortex properties in a turbulent boundary layer

    Science.gov (United States)

    Ganapathisubramani, Bharathram; Longmire, Ellen K.; Marusic, Ivan

    2006-05-01

    Dual-plane particle image velocimetry experiments were performed in a turbulent boundary layer with Reτ=1160 to obtain all components of the velocity gradient tensor. Wall-normal locations in the logarithmic and wake region were examined. The availability of the complete gradient tensor facilitates improved identification of vortex cores and determination of their orientation and size. Inclination angles of vortex cores were computed using statistical tools such as two-point correlations and joint probability density functions. Also, a vortex identification technique was employed to identify individual cores and to compute inclination angles directly from instantaneous fields. The results reveal broad distributions of inclination angles at both locations. The results are consistent with the presence of many hairpin vortices which are most frequently inclined downstream at an angle of 45∘ with the wall. According to the probability density functions, a relatively small percentage of cores are inclined upstream. The number density of forward leaning cores decreases from the logarithmic to the outer region while the number density of backward-leaning cores remains relatively constant. These trends, together with the correlation statistics, suggest that the backward-leaning cores are part of smaller, weaker structures that have been distorted and convected by larger, predominantly forward-leaning eddies associated with the local shear.

  2. Vortex Formation Behind an Inclined 2-Dimensional Thin Flat Plate

    Science.gov (United States)

    Mohebi, Meraj; Wood, David H.; Martinuzzi, Robert J.

    2014-11-01

    Stereo Particle Image Velocimetry was used to measure the turbulent wake of a 2D flat plate inclined relative to a uniform stream as a heuristic model for airfoils and wind turbine blades at high incidence. Phase Averaging was performed to study the vortex dynamics and relate these to the force characteristics. Below 90°, immediately behind the plate, rounder and more organized trailing edge vortices form which possess higher circulation and are associated with higher Reynolds stresses than the counter-rotating, weaker and elongated leading edge vortices. The quasi-periodically shed vortices on the sides of the wake decay in strength at different rates to reach a circulation ratio of -1 within a distance less than 5 chords downstream of the plate for all angles. This equalization of vortex strength is related to an increase in turbulence diffusion, due to mostly-incoherent 3-dimensionality which progressively increases as the inclination angle is reduced, and convective transfer of vorticity between counter-rotating vortices. The wake experiences a sudden change in vortex formation mechanism at around 40°. At this angle, the frequency analysis on the signals of a pair of micro-pressure transducers in the wake also shows a discontinuity in the trends. This work was supported by NSERC Discovery grants to R. J. Martinuzzi and D. H. Wood.

  3. Aperiodicity Correction for Rotor Tip Vortex Measurements

    Science.gov (United States)

    Ramasamy, Manikandan; Paetzel, Ryan; Bhagwat, Mahendra J.

    2011-01-01

    The initial roll-up of a tip vortex trailing from a model-scale, hovering rotor was measured using particle image velocimetry. The unique feature of the measurements was that a microscope was attached to the camera to allow much higher spatial resolution than hitherto possible. This also posed some unique challenges. In particular, the existing methodologies to correct for aperiodicity in the tip vortex locations could not be easily extended to the present measurements. The difficulty stemmed from the inability to accurately determine the vortex center, which is a prerequisite for the correction procedure. A new method is proposed for determining the vortex center, as well as the vortex core properties, using a least-squares fit approach. This approach has the obvious advantage that the properties are derived from not just a few points near the vortex core, but from a much larger area of flow measurements. Results clearly demonstrate the advantage in the form of reduced variation in the estimated core properties, and also the self-consistent results obtained using three different aperiodicity correction methods.

  4. Counterexamples to Moffatt's statements on vortex knots.

    Science.gov (United States)

    Bogoyavlenskij, Oleg

    2017-04-01

    One of the well-known problems of hydrodynamics is studied: the problem of classification of vortex knots for ideal fluid flows. In the literature there are known Moffatt statements that all torus knots K_{m,n} for all rational numbers m/n (0vortex knots for each one of the considered axisymmetric fluid flows. We prove that actually such a uniformity does not exist because it does not correspond to the facts. Namely, we derive a complete classification of all vortex knots realized for the fluid flows studied by Moffatt and demonstrate that the real structure of vortex knots is much more rich because the sets of mutually nonisotopic vortex knots realized for different axisymmetric fluid flows are all different. An exact formula for the limit of the hydrodynamic safety factor q_{h} at a vortex axis is derived for arbitrary axisymmetric fluid equilibria. Another exact formula is obtained for the limit of the magnetohydrodynamics safety factor q at a magnetic axis for the general axisymmetric plasma equilibria.

  5. Experimental study of vortex breakdown in a cylindrical, swirling flow

    Science.gov (United States)

    Stevens, J. L.; Celik, Z. Z.; Cantwell, B. J.; Lopez, J. M.

    1996-01-01

    The stability of a steady, vortical flow in a cylindrical container with one rotating endwall has been experimentally examined to gain insight into the process of vortex breakdowwn. The dynamics of the flow are governed by the Reynolds number (Re) and the aspect ratio of the cylinder. Re is given by Omega R(sup 2)/nu, where Omega is the speed of rotation of the endwall, R is the cylinder radius, and nu is the kinematic viscosity of the fluid filling the cylinder. The aspect ratio is H/R, where H is the height of the cylinder. Numerical simulation studies disagree whether or not the steady breakdown is stable beyond a critical Reynolds number, Re(sub c). Previous experimental researches have considered the steady and unsteady flows near Re(sub c), but have not explored the stability of the steady breakdown structures beyond this value. In this investigation, laser induced fluorescence was utilized to observe both steady and unsteady vortex breakdown at a fixed H/R of 2.5 with Re varying around Re(sub c). When the Re of a steady flow was slowly increased beyond Re(sub c), the breakdown structure remained steady even though unsteadiness was possible. In addition, a number of hysteresis events involving the oscillation periods of the unsteady flow were noted. The results show that both steady and unsteady vortex breakdown occur for a limited range of Re above Re(sub c). Also, with increasing Re, complex flow transformations take place that alter the period at which the unsteady flow oscillates.

  6. Bluff Body Flow Simulation Using a Vortex Element Method

    Energy Technology Data Exchange (ETDEWEB)

    Anthony Leonard; Phillippe Chatelain; Michael Rebel

    2004-09-30

    Heavy ground vehicles, especially those involved in long-haul freight transportation, consume a significant part of our nation's energy supply. it is therefore of utmost importance to improve their efficiency, both to reduce emissions and to decrease reliance on imported oil. At highway speeds, more than half of the power consumed by a typical semi truck goes into overcoming aerodynamic drag, a fraction which increases with speed and crosswind. Thanks to better tools and increased awareness, recent years have seen substantial aerodynamic improvements by the truck industry, such as tractor/trailer height matching, radiator area reduction, and swept fairings. However, there remains substantial room for improvement as understanding of turbulent fluid dynamics grows. The group's research effort focused on vortex particle methods, a novel approach for computational fluid dynamics (CFD). Where common CFD methods solve or model the Navier-Stokes equations on a grid which stretches from the truck surface outward, vortex particle methods solve the vorticity equation on a Lagrangian basis of smooth particles and do not require a grid. They worked to advance the state of the art in vortex particle methods, improving their ability to handle the complicated, high Reynolds number flow around heavy vehicles. Specific challenges that they have addressed include finding strategies to accurate capture vorticity generation and resultant forces at the truck wall, handling the aerodynamics of spinning bodies such as tires, application of the method to the GTS model, computation time reduction through improved integration methods, a closest point transform for particle method in complex geometrics, and work on large eddy simulation (LES) turbulence modeling.

  7. Performance evaluation of a dual linear ion trap-Fourier transform ion cyclotron resonance mass spectrometer for proteomics research.

    Science.gov (United States)

    Weisbrod, Chad R; Hoopmann, Michael R; Senko, Michael W; Bruce, James E

    2013-08-02

    A novel dual cell linear ion trap Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) and its performance characteristics are reported. A linear ion trap-Fourier transform ion cyclotron resonance mass spectrometer has been modified to incorporate a LTQ-Velos mass spectrometer. This modified instrument features efficient ion accumulation and fast MS/MS acquisition capabilities of dual cell linear RF ion trap instruments coupled to the high mass accuracy, resolution, and dynamic range of a FT-ICR for improved proteomic coverage. The ion accumulation efficiency is demonstrated to be an order of magnitude greater than that observed with LTQ-FT Ultra instrumentation. The proteome coverage with yeast was shown to increase over the previous instrument generation by 50% (100% increase on the peptide level). In addition, many lower abundance level yeast proteins were only detected with this modified instrument. This novel configuration also enables beam type CID fragmentation using a dual cell RF ion trap mass spectrometer. This technique involves accelerating ions between traps while applying an elevated DC offset to one of the traps to accelerate ions and induce fragmentation. This instrument design may serve as a useful option for labs currently considering purchasing new instrumentation or upgrading existing instruments. A novel hybrid mass spectrometer that allows increased MS/MS acquisition rates with high mass measurement accuracy and new ion fragmentation methods greatly improves the number of proteins, posttranslational modifications and protein-protein interactions that can be identified from cells. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Improved Methodology for Monitoring Poly(amidoamine Dendrimers Surface Transformations and Product Quality by Ultra Performance Liquid Chromatography

    Directory of Open Access Journals (Sweden)

    Chevelle A. Cason

    2008-01-01

    Full Text Available Ultra performance liquid chromatography (UPLC analysis was utilized for the first time as a methodology for monitoring poly(amidoamine (PAMAM dendrimer surface transformations and product quality. Results were compared to high-performance liquid chromatography (HPLC and were found to provide a vastly improved analytical method for the characterization of dendrimer polydispersity and variance in a typical surface modification. The application of UPLC increased the average number of theoretical plates by a factor of 7 and reduced retention times of analytes by 36%, while improving the resolution capability to discriminate surface variances in dendrimers. The new UPLC procedures were used to monitor surface modification of [core: ethylenediamine]; (G = 4; dendri-poly(amidoamine-(NH264 (i.e., [EDA]; (G4; dendri-PAMAM-(NH264 to produce biotinylated dendrimer conjugates. The enhanced sensitivity and efficiency of the UPLC analyses allowed resolution of biotin substituent levels and a better characterization of the targeted dendrimer conjugates compared to traditional HPLC methodology.

  9. A chirped-pulse Fourier-transform microwave/pulsed uniform flow spectrometer. II. Performance and applications for reaction dynamics

    Science.gov (United States)

    Abeysekera, Chamara; Zack, Lindsay N.; Park, G. Barratt; Joalland, Baptiste; Oldham, James M.; Prozument, Kirill; Ariyasingha, Nuwandi M.; Sims, Ian R.; Field, Robert W.; Suits, Arthur G.

    2014-12-01

    This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in pulsed uniform flows. Here we detail the development and testing of a new Ka-band CP-FTMW spectrometer in combination with the pulsed flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys. 141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.

  10. Applicability of a Diffuse Reflectance Infrared Fourier Transform handheld spectrometer to perform in situ analyses on Cultural Heritage materials

    Science.gov (United States)

    Arrizabalaga, Iker; Gómez-Laserna, Olivia; Aramendia, Julene; Arana, Gorka; Madariaga, Juan Manuel

    2014-08-01

    This work studies the applicability of a Diffuse Reflectance Infrared Fourier Transform handheld device to perform in situ analyses on Cultural Heritage assets. This portable diffuse reflectance spectrometer has been used to characterise and diagnose the conservation state of (a) building materials of the Guevara Palace (15th century, Segura, Basque Country, Spain) and (b) different 19th century wallpapers manufactured by the Santa Isabel factory (Vitoria-Gasteiz, Basque Country, Spain) and by the well known Dufour and Leroy manufacturers (Paris, France), all of them belonging to the Torre de los Varona Castle (Villanañe, Basque Country, Spain). In all cases, in situ measurements were carried out and also a few samples were collected and measured in the laboratory by diffuse reflectance spectroscopy (DRIFT) in order to validate the information obtained by the handheld instrument. In the analyses performed in situ, distortions in the diffuse reflectance spectra can be observed due to the presence of specular reflection, showing the inverted bands caused by the Reststrahlen effect, in particular on those IR bands with the highest absorption coefficients. This paper concludes that the results obtained in situ by a diffuse reflectance handheld device are comparable to those obtained with laboratory diffuse reflectance spectroscopy equipment and proposes a few guidelines to acquire good spectra in the field, minimising the influence caused by the specular reflection.

  11. Signal noise ratio analysis and on-orbit performance estimation of a solar occultation Fourier transform spectrometer

    Science.gov (United States)

    Li, Bicen; Xu, Pengmei; Hou, Lizhou; Wang, Caiqin

    2017-10-01

    Taking the advantages of high spectral resolution, high sensitivity and wide spectral coverage, space borne Fourier transform infrared spectrometer (FTS) plays more and more important role in atmospheric composition sounding. The combination of solar occultation and FTS technique improves the sensitivity of instrument. To achieve both high spectral resolution and high signal to noise ratio (SNR), reasonable allocation and optimization for instrument parameters are the foundation and difficulty. The solar occultation FTS (SOFTS) is a high spectral resolution (0.03 cm-1) FTS operating from 2.4 to 13.3 μm (750-4100cm-1), which will determine the altitude profile information of typical 10-100km for temperature, pressure, and the volume mixing ratios for several dozens of atmospheric compositions. As key performance of SOFTS, SNR is crucially important to high accuracy retrieval of atmospheric composition, which is required to be no less than 100:1 at the radiance of 5800K blackbody. Based on the study of various parameters and its interacting principle, according to interference theory and operation principle of time modulated FTS, a simulation model of FTS SNR has been built, which considers satellite orbit, spectral radiometric features of sun and atmospheric composition, optical system, interferometer and its control system, measurement duration, detector sensitivity, noise of detector and electronic system and so on. According to the testing results of SNR at the illuminating of 1000 blackbody, the on-orbit SNR performance of SOFTS is estimated, which can meet the mission requirement.

  12. Applicability of a Diffuse Reflectance Infrared Fourier Transform handheld spectrometer to perform in situ analyses on Cultural Heritage materials.

    Science.gov (United States)

    Arrizabalaga, Iker; Gómez-Laserna, Olivia; Aramendia, Julene; Arana, Gorka; Madariaga, Juan Manuel

    2014-08-14

    This work studies the applicability of a Diffuse Reflectance Infrared Fourier Transform handheld device to perform in situ analyses on Cultural Heritage assets. This portable diffuse reflectance spectrometer has been used to characterise and diagnose the conservation state of (a) building materials of the Guevara Palace (15th century, Segura, Basque Country, Spain) and (b) different 19th century wallpapers manufactured by the Santa Isabel factory (Vitoria-Gasteiz, Basque Country, Spain) and by the well known Dufour and Leroy manufacturers (Paris, France), all of them belonging to the Torre de los Varona Castle (Villanañe, Basque Country, Spain). In all cases, in situ measurements were carried out and also a few samples were collected and measured in the laboratory by diffuse reflectance spectroscopy (DRIFT) in order to validate the information obtained by the handheld instrument. In the analyses performed in situ, distortions in the diffuse reflectance spectra can be observed due to the presence of specular reflection, showing the inverted bands caused by the Reststrahlen effect, in particular on those IR bands with the highest absorption coefficients. This paper concludes that the results obtained in situ by a diffuse reflectance handheld device are comparable to those obtained with laboratory diffuse reflectance spectroscopy equipment and proposes a few guidelines to acquire good spectra in the field, minimising the influence caused by the specular reflection. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Tunable-wavelength picosecond vortex generation in fiber and its application in frequency-doubled vortex

    Science.gov (United States)

    Zhang, Wending; Wei, Keyan; Wang, Heng; Mao, Dong; Gao, Feng; Huang, Ligang; Mei, Ting; Zhao, Jianlin

    2018-01-01

    We present a method for tunable-wavelength picosecond vortex pulse generation by using an acoustically-induced fiber grating (AIFG). The AIFG-driven mode conversion characteristic was activated via a shear-mode piezoelectric transducer that excels in excitation efficiency of acoustic flexural wave and mechanical stability. The linearly-polarized ±1-order picosecond vortex pulse was experimentally generated via AIFG with a uniform coupling efficiency of ∼98.4% from the fundamental mode to the ±1-order vortex mode within the wavelength range 1540 nm ∼ 1560 nm. The topological charge and the linearly-polarized characteristic of the picosecond vortex pulse were verified by examination of the off-axial interference and the polarization angle-dependent intensity, respectively. Furthermore, the picosecond vortex pulse with wavelength tunability was input to a nonlinear BBO crystal to generate a frequency-doubled ±2-order vortex in the wavelength range 770 nm ∼ 780 nm. This technology provides a convenient apparatus for generating a picosecond vortex pulse and the frequency-doubled vortex with wavelength tunability.

  14. Sculptured 3D twister superlattices embedded with tunable vortex spirals.

    Science.gov (United States)

    Xavier, Jolly; Vyas, Sunil; Senthilkumaran, Paramasivam; Denz, Cornelia; Joseph, Joby

    2011-09-01

    We present diverse reconfigurable complex 3D twister vortex superlattice structures in a large area embedded with tunable vortex spirals as well as dark rings, threaded by vortex helices. We demonstrate these tunable complex chiral vortex superlattices by the superposition of relatively phase engineered plane waves. The generated complex 3D twister lattice vortex structures are computationally as well as experimentally analyzed using various tools to verify the presence of phase singularities. Our observation indicates the application-specific flexibility of our approach to tailor the transverse superlattice spatial irradiance profile of these longitudinally whirling vortex-cluster units and dark rings.

  15. Application of Impedance Microbiology for Evaluating Potential Acidifying Performances of Starter Lactic Acid Bacteria to Employ in Milk Transformation.

    Science.gov (United States)

    Bancalari, Elena; Bernini, Valentina; Bottari, Benedetta; Neviani, Erasmo; Gatti, Monica

    2016-01-01

    Impedance microbiology is a method that enables tracing microbial growth by measuring the change in the electrical conductivity. Different systems, able to perform this measurement, are available in commerce and are commonly used for food control analysis by mean of measuring a point of the impedance curve, defined "time of detection." With this work we wanted to find an objective way to interpret the metabolic significance of impedance curves and propose it as a valid approach to evaluate the potential acidifying performances of starter lactic acid bacteria to be employed in milk transformation. To do this it was firstly investigated the possibility to use the Gompertz equation to describe the data coming from the impedance curve obtained by mean of BacTrac 4300®. Lag time (λ), maximum specific M% rate (μmax), and maximum value of M% (Yend) have been calculated and, given the similarity of the impedance fitted curve to the bacterial growth curve, their meaning has been interpreted. Potential acidifying performances of eighty strains belonging to Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis, and Streptococcus thermophilus species have been evaluated by using the kinetics parameters, obtained from Excel add-in DMFit version 2.1. The novelty and importance of our findings, obtained by means of BacTrac 4300®, is that they can also be applied to data obtained from other devices. Moreover, the meaning of λ, μmax, and Yend that we have extrapolated from Modified Gompertz equation and discussed for lactic acid bacteria in milk, can be exploited also to other food environment or other bacteria, assuming that they can give a curve and that curve is properly fitted with Gompertz equation.

  16. Effect of Ripple Geometry on Vortex Generation, Ejection, and Strength in Oscillatory Flow

    Science.gov (United States)

    Smith, H. D.

    2012-12-01

    Turbulent vortex structures generated around bedforms have a large potential for significant suspended sediment transport. In the nearshore, the flow separation over ripples results in the generation of a lee vortex that can entrain sediment during half of the wave cycle. As the flow reverses, the sediment-laden vortex is ejected into the water column. The vortex is translated with the reversed flow and dissipates, releasing its sediment load back to the bed. The generation and ejection processes are functions of the ripple geometry and the wave acceleration. These same processes are also present for other geometries placed near the sea bed. Studies around bottom-seated cylindrical structures have shown multiple generation and ejection events off of the lee of the cylinder during half of the wave cycle. This generation is a function of Keulegan-Carpenter number, which balances the semi-excursion of the wave to the dominant length scale of the structure. In this work, the flow over rippled beds of various geometries over a range of hydrodynamic forcing will be numerically simulated to investigate the generation, ejection mechanisms, and strength of vortices created by this interaction. The simulations will be performed with the finite-difference CFD model, FLOW-3D. An advantage to this model is its ability to resolve complicated geometries in the flow with cartesian grids. In order to resolve the complex, three-dimensional flow field over an approximately two-dimensional rippled bed, a Smagorinsky Large Eddy Simulation closure scheme will be utilized. This model configuration has been shown to accurately predict the lift and drag force coefficients for bottom-mounted cylinders under linear waves, which are dominated by vortex generation and ejection. The three-dimensional vortex structure and strength will be evaluated with swirling strength criterion. Three-dimensional isosurfaces of the swirling strength will allow for the visual identification of the interaction

  17. Vortex system studies on small wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Montgomerie, Bjoern; Dahlberg, Jan-Aake [Swedish Defence Research Agency, Stockholm (Sweden). Div. of Aeronautics, FFA

    2003-10-01

    The wind tunnel experiment reported included a small wind turbine setup and smoke to visualize the trailing tip vortices for different wind turbine configurations. Several combinations of tunnel wind speeds and tip speed ratios generated a database where the end result functions were radius and pitch, of the tip vortex spirals, versus the downstream coordinate. The Reynolds number in the experiment was very low compared to that of full size turbines. The results should therefore be seen as valid only for low Reynolds numbers. The models were 18 and 25 cm diameter turbines. This is thought to be complementary to the information obtained in similar wind tunnel investigations for much larger models. The database is meant to be a fundamental tool for the construction of practical aerodynamic induction methods. Such methods typically employ the Biot-Savart law has been shown to lead to a flow field, which deviates considerably from that of reality. E.g. concentration into tip vortices does not happen when the flow is simulated with Biot-Savart law only. Thus, a combination of the induction method and its modification, based on investigations such as the one reported, is foreseen to replace the widely used Blade Element Momentum method for wind turbine loads and performance prediction.

  18. Optical vortex metrology: Are phase singularities foes or friends in optical metrology?

    DEFF Research Database (Denmark)

    Takeda, M.; Wang, W.; Hanson, Steen Grüner

    2008-01-01

    We raise an issue whether phase singularities are foes or friends in optical metrology, and give an answer by introducing the principle and applications of a new technique which we recently proposed for displacement and flow measurements. The technique is called optical vortex metrology because i...... or Laguerre-Gauss transform to the random pattern. © (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only....

  19. Intraventricular vortex properties in nonischemic dilated cardiomyopathy.

    Science.gov (United States)

    Bermejo, Javier; Benito, Yolanda; Alhama, Marta; Yotti, Raquel; Martínez-Legazpi, Pablo; Del Villar, Candelas Pérez; Pérez-David, Esther; González-Mansilla, Ana; Santa-Marta, Cristina; Barrio, Alicia; Fernández-Avilés, Francisco; Del Álamo, Juan C

    2014-03-01

    Vortices may have a role in optimizing the mechanical efficiency and blood mixing of the left ventricle (LV). We aimed to characterize the size, position, circulation, and kinetic energy (KE) of LV main vortex cores in patients with nonischemic dilated cardiomyopathy (NIDCM) and analyze their physiological correlates. We used digital processing of color-Doppler images to study flow evolution in 61 patients with NIDCM and 61 age-matched control subjects. Vortex features showed a characteristic biphasic temporal course during diastole. Because late filling contributed significantly to flow entrainment, vortex KE reached its maximum at the time of the peak A wave, storing 26 ± 20% of total KE delivered by inflow (range: 1-74%). Patients with NIDCM showed larger and stronger vortices than control subjects (circulation: 0.008 ± 0.007 vs. 0.006 ± 0.005 m(2)/s, respectively, P = 0.02; KE: 7 ± 8 vs. 5 ± 5 mJ/m, P = 0.04), even when corrected for LV size. This helped confining the filling jet in the dilated ventricle. The vortex Reynolds number was also higher in the NIDCM group. By multivariate analysis, vortex KE was related to the KE generated by inflow and to chamber short-axis diameter. In 21 patients studied head to head, Doppler measurements of circulation and KE closely correlated with phase-contract magnetic resonance values (intraclass correlation coefficient = 0.82 and 0.76, respectively). Thus, the biphasic nature of filling determines normal vortex physiology. Vortex formation is exaggerated in patients with NIDCM due to chamber remodeling, and enlarged vortices are helpful for ameliorating convective pressure losses and facilitating transport. These findings can be accurately studied using ultrasound.

  20. Relation between current sheets and vortex sheets in stationary incompressible MHD

    Directory of Open Access Journals (Sweden)

    D. H. Nickeler

    2012-03-01

    Full Text Available Magnetohydrodynamic configurations with strong localized current concentrations and vortices play an important role in the dissipation of energy in space and astrophysical plasma. Within this work we investigate the relation between current sheets and vortex sheets in incompressible, stationary equilibria. For this approach it is helpful that the similar mathematical structure of magnetohydrostatics and stationary incompressible hydrodynamics allows us to transform static equilibria into stationary ones. The main control function for such a transformation is the profile of the Alfvén-Mach number MA, which is always constant along magnetic field lines, but can change from one field line to another. In the case of a global constant MA, vortices and electric current concentrations are parallel. More interesting is the nonlinear case, where MA varies perpendicular to the field lines. This is a typical situation at boundary layers like the magnetopause, heliopause, the solar wind flowing around helmet streamers and at the boundary of solar coronal holes. The corresponding current and vortex sheets show in some cases also an alignment, but not in every case. For special density distributions in 2-D, it is possible to have current but no vortex sheets. In 2-D, vortex sheets of field aligned-flows can also exist without strong current sheets, taking the limit of small Alfvén Mach numbers into account. The current sheet can vanish if the Alfvén Mach number is (almost constant and the density gradient is large across some boundary layer. It should be emphasized that the used theory is not only valid for small Alfvén Mach numbers MA MA ≲ 1. Connection to other theoretical approaches and observations and physical effects in space plasmas are presented. Differences in the various aspects of theoretical investigations of current sheets and vortex sheets are given.

  1. Transient electromagnetic simulations of substation earth grid for improving lightning withstand performance of a large power transformer

    DEFF Research Database (Denmark)

    Bak, Claus Leth; Einarsdottir, Kristin E.; Andresson, Einar

    connections are analyzed with respect to lightning overvoltage at the transformer bushings and it is shown clearly that the layout of the grounding system in the vicinity of the surge arrester down conductors plays an important role for the magnitude of the transformer bushing overvoltage during lightnings...

  2. Detection of posterior vortex veins in eyes with pathologic myopia by ultra-widefield indocyanine green angiography.

    Science.gov (United States)

    Moriyama, Muka; Cao, Kejia; Ogata, Satoko; Ohno-Matsui, Kyoko

    2017-09-01

    To analyse the characteristics of posterior vortex veins detected in highly myopic eyes by wide-field indocyanine green angiography (ICGA). One hundred and fifty-eight consecutive patients (302 eyes) with high myopia (myopic refractive error >8.0 dioptres (D) or axial length ≥26.5 mm) were studied. Wide-field ICGA was performed with the Spectralis HRA module. Posterior vortex veins were found in 80 eyes (26%). The prevalence of posterior staphyloma was significantly higher in eyes in which posterior vortex vein was detected than in eyes without posterior vortex vein. The posterior vortex veins were classified into five types according to the site of exit from the eye; around the optic nerve in 28%, in the macular area in 17%, along the border of staphyloma in 6%, along the margin of macular atrophy or large peripapillary conus in 21%, and elsewhere in 28%. In one eye, two posterior vortex veins collected the choroidal venous blood from the entire fundus. Wide-field ICGA can analyse the characteristic features of choroidal blood outflow system through posterior vortex veins in highly myopic eyes. They may play an important role as routes of choroidal outflow in highly myopic eyes. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  3. Measurement of Turbulent Fluxes of Swirling Flow in a Scaled Up Multi Inlet Vortex Reactor

    Science.gov (United States)

    Olsen, Michael; Hitimana, Emmanual; Hill, James; Fox, Rodney

    2017-11-01

    The multi-inlet vortex reactor (MIVR) has been developed for use in the FlashNanoprecipitation (FNP) process. The MIVR has four identical square inlets connected to a central cylindrical mixing chamber with one common outlet creating a highly turbulent swirling flow dominated by a strong vortex in the center. Efficient FNP requires rapid mixing within the MIVR. To investigate the mixing, instantaneous velocity and concentration fields were acquired using simultaneous stereoscopic particle image velocimetry and planar laser-induced fluorescence. The simultaneous velocity and concentration data were used to determine turbulent fluxes and spatial cross-correlations of velocity and concentration fluctuations. The measurements were performed for four inlet flow Reynolds numbers (3250, 4875, 6500, and 8125) and at three measurement planes within the reactor. A correlation between turbulent fluxes and vortex strength was found. For all Reynolds numbers, turbulent fluxes are maximum in the vortex dominated central region of the reactor and decay away from the vortex. Increasing Reynolds number increased turbulent fluxes and subsequently enhanced mixing. The mixing performance was confirmed by determining coefficients of concentration variance within the reactor.

  4. Transformation from Film to Nanorod via a Sacrifical Layer: Pulsed Laser Deposition of ZnO for Enhancing Photodetector Performance.

    Science.gov (United States)

    Ou, Sin-Liang; Yu, Fei-Peng; Wuu, Dong-Sing

    2017-10-27

    A novel fabrication method for single crystalline ZnO nanorods by pulsed laser deposition (PLD) using a chemical-bath-deposited ZnS seed layer is proposed. For the substrate temperature (Ts) lower than 700 °C, the PLD-ZnO showed a polycrystalline phase and film-type morphology, resulting from the ZnS seed layer with a cubic phase. However, the ZnS film became a sacrifical layer and single crystalline ZnO(002) nanorods can be achieved at Ts of 900 °C, where ZnS was decomposed to zinc metals and sulfur fumes. The transformation from ZnO film to nanorod microstructure was demonstrated with the change of ZnS layer into Zn grains. Enhanced performance of the metal-semiconductor-metal photodetectors were fabricated with ZnO/ZnS samples grown at Ts of 500, 700, and 900 °C. The responsivities (@1 V and 370 nm) of these three devices were 1.71, 6.35, and 98.67 A/W, while their UV-to-visible discrimination ratios were 7.2, 16.5, and 439.1, respectively. Obviously, a higher light-capturing efficiency was obtained in the 900 °C-grown ZnO/ZnS device owing to its one-dimensional nanostructure with high crystal quality. The results indicate PLD combined with a sacrifical nanostructure is a promising method for obtaining high-quality ZnO nanorods, which paves the way for the fabrication of high performance ZnO-based devices.

  5. Vortices and vortex lattices in quantum ferrofluids.

    Science.gov (United States)

    Martin, A M; Marchant, N G; O'Dell, D H J; Parker, N G

    2017-03-15

    The experimental realization of quantum-degenerate Bose gases made of atoms with sizeable magnetic dipole moments has created a new type of fluid, known as a quantum ferrofluid, which combines the extraordinary properties of superfluidity and ferrofluidity. A hallmark of superfluids is that they are constrained to rotate through vortices with quantized circulation. In quantum ferrofluids the long-range dipolar interactions add new ingredients by inducing magnetostriction and instabilities, and also affect the structural properties of vortices and vortex lattices. Here we give a review of the theory of vortices in dipolar Bose-Einstein condensates, exploring the interplay of magnetism with vorticity and contrasting this with the established behaviour in non-dipolar condensates. We cover single vortex solutions, including structure, energy and stability, vortex pairs, including interactions and dynamics, and also vortex lattices. Our discussion is founded on the mean-field theory provided by the dipolar Gross-Pitaevskii equation, ranging from analytic treatments based on the Thomas-Fermi (hydrodynamic) and variational approaches to full numerical simulations. Routes for generating vortices in dipolar condensates are discussed, with particular attention paid to rotating condensates, where surface instabilities drive the nucleation of vortices, and lead to the emergence of rich and varied vortex lattice structures. We also present an outlook, including potential extensions to degenerate Fermi gases, quantum Hall physics, toroidal systems and the Berezinskii-Kosterlitz-Thouless transition.

  6. Vortex Shedding Inside a Baffled Air Duct

    Science.gov (United States)

    Davis, Philip; Kenny, R. Jeremy

    2010-01-01

    Common in the operation of both segmented and un-segmented large solid rocket motors is the occurrence of vortex shedding within the motor chamber. A portion of the energy within a shed vortex is converted to acoustic energy, potentially driving the longitudinal acoustic modes of the motor in a quasi-discrete fashion. This vortex shedding-acoustic mode excitation event occurs for every Reusable Solid Rocket Motor (RSRM) operation, giving rise to subsequent axial thrust oscillations. In order to better understand this vortex shedding/acoustic mode excitation phenomena, unsteady CFD simulations were run for both a test geometry and the full scale RSRM geometry. This paper covers the results from the subscale geometry runs, which were based on work focusing on the RSRM hydrodynamics. Unsteady CFD simulation parameters, including boundary conditions and post-processing returns, are reviewed. The results were further post-processed to identify active acoustic modes and vortex shedding characteristics. Probable locations for acoustic energy generation, and subsequent acoustic mode excitation, are discussed.

  7. Vortex stretching in a homogeneous isotropic turbulence

    Science.gov (United States)

    Hirota, M.; Nishio, Y.; Izawa, S.; Fukunishi, Y.

    2017-04-01

    Stretching vortices whose sizes are in the inertial subrange of a homogeneous isotropic turbulence are picked up, and the geometric relations with the neighboring vortices whose scales are twice larger are studied. Hierarchical vortices are extracted using a Fourier band-pass filter, and each extracted vortex is reconstructed as a set of short cylindrical segments along the vortex axis to discuss the vortex interactions. As a result, it is shown that the directions of larger vortices near the segments of the fast stretching vortices tend to be orthogonal to the direction of the stretching segments, and the locations of the larger vortices that contribute most to the stretching of smaller vortex segments are likely to be found in the direction with the relative angle of 45° from the axes of the stretching vortex segments. And, the vortices with the second highest contributions tend to be in the directions 45° from the stretching segments’ axes and orthogonal to the directions of the highest contributing vortices.

  8. The Effect of Orifice Diameter to the Acoustic Signals Captured at the Cold Part of a Ranque-Hilsch Vortex Tube

    Directory of Open Access Journals (Sweden)

    Wisnoe Wirachman

    2017-01-01

    Full Text Available In this study, acoustic analysis and thermofluid performance of a Ranque-Hilsch Vortex Tube (RHVT is experimentally investigated under different orifice diameters at its cold tube. The orifice diameters used are 2mm, 3 mm, 4 mm, 5 mm and 6 mm. The inlet pressure (gage is set at 10 psi, 15 psi, 20 psi and 25 psi for each orifice diameter. The sound produced by the tube is recorded using a microphone located outside the cold tube. The acoustic signal is processed using Fast-Fourier Transform (FFT to obtain the frequency representation. Main frequencies are then extracted to constitute the signature of the signal for that specific configuration. It is observed that different orifice diameters give different signatures. These signatures are then associated with the thermofluid performance of the device to obtain the relation among the parameters.

  9. Atmospheric effects on microphone array analysis of aircraft vortex sound

    Science.gov (United States)

    2006-05-08

    This paper provides the basis of a comprehensive analysis of vortex sound propagation : through the atmosphere in order to assess real atmospheric effects on acoustic array : processing. Such effects may impact vortex localization accuracy and detect...

  10. Numerical Study of Microscale Shock-Vortex Interaction

    Directory of Open Access Journals (Sweden)

    Hong Xiao

    2015-01-01

    Full Text Available Numerical studies of microscale shock-vortex interaction were conducted by particle-based direct simulation of Monte Carlo (DSMC. The enstrophy is found to be increased in the strong microscale shock-vortex interaction, which is not observed in the previous DSMC studies within the limited cases. Investigations also show that the increase of the enstrophy results in an increase in dissipation rate during the strong interaction. The incoming Mach number, vortex size, and vortex Mach number turn out to play a critical role in the strength of interaction, which in turn govern the change in the dissipation rate and the increase or decrease in enstrophy during the microscale shock-vortex interaction. It is also observed that the incoming Mach number is the most dominant parameter, followed by vortex size and vortex Mach number, during the microscale shock-vortex interaction.

  11. Bitter decoration and magneto-optical observations of vortex chains ...

    Indian Academy of Sciences (India)

    dimensional arrangements, called vortex chains. We have visualized vortex chains by Bitter decoration and magneto-optical technique. The fundamental energy scale for the attractive interaction between pancake and Josephson vortices is evaluated ...

  12. Vortex Filaments in Grids for Scalable, Fine Smoke Simulation.

    Science.gov (United States)

    Meng, Zhang; Weixin, Si; Yinling, Qian; Hanqiu, Sun; Jing, Qin; Heng, Pheng-Ann

    2015-01-01

    Vortex modeling can produce attractive visual effects of dynamic fluids, which are widely applicable for dynamic media, computer games, special effects, and virtual reality systems. However, it is challenging to effectively simulate intensive and fine detailed fluids such as smoke with fast increasing vortex filaments and smoke particles. The authors propose a novel vortex filaments in grids scheme in which the uniform grids dynamically bridge the vortex filaments and smoke particles for scalable, fine smoke simulation with macroscopic vortex structures. Using the vortex model, their approach supports the trade-off between simulation speed and scale of details. After computing the whole velocity, external control can be easily exerted on the embedded grid to guide the vortex-based smoke motion. The experimental results demonstrate the efficiency of using the proposed scheme for a visually plausible smoke simulation with macroscopic vortex structures.

  13. Dynamic control of collapse in a vortex Airy beam.

    Science.gov (United States)

    Chen, Rui-Pin; Chew, Khian-Hooi; He, Sailing

    2013-01-01

    Here we study systematically the self-focusing dynamics and collapse of vortex Airy optical beams in a Kerr medium. The collapse is suppressed compared to a non-vortex Airy beam in a Kerr medium due to the existence of vortex fields. The locations of collapse depend sensitively on the initial power, vortex order, and modulation parameters. The collapse may occur in a position where the initial field is nearly zero, while no collapse appears in the region where the initial field is mainly distributed. Compared with a non-vortex Airy beam, the collapse of a vortex Airy beam can occur at a position away from the area of the initial field distribution. Our study shows the possibility of controlling and manipulating the collapse, especially the precise position of collapse, by purposely choosing appropriate initial power, vortex order or modulation parameters of a vortex Airy beam.

  14. Front propagation in a regular vortex lattice: Dependence on the vortex structure

    Science.gov (United States)

    Beauvier, E.; Bodea, S.; Pocheau, A.

    2017-11-01

    We investigate the dependence on the vortex structure of the propagation of fronts in stirred flows. For this, we consider a regular set of vortices whose structure is changed by varying both their boundary conditions and their aspect ratios. These configurations are investigated experimentally in autocatalytic solutions stirred by electroconvective flows and numerically from kinematic simulations based on the determination of the dominant Fourier mode of the vortex stream function in each of them. For free lateral boundary conditions, i.e., in an extended vortex lattice, it is found that both the flow structure and the front propagation negligibly depend on vortex aspect ratios. For rigid lateral boundary conditions, i.e., in a vortex chain, vortices involve a slight dependence on their aspect ratios which surprisingly yields a noticeable decrease of the enhancement of front velocity by flow advection. These different behaviors reveal a sensitivity of the mean front velocity on the flow subscales. It emphasizes the intrinsic multiscale nature of front propagation in stirred flows and the need to take into account not only the intensity of vortex flows but also their inner structure to determine front propagation at a large scale. Differences between experiments and simulations suggest the occurrence of secondary flows in vortex chains at large velocity and large aspect ratios.

  15. Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.

    2007-01-01

    High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.

  16. Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

    Science.gov (United States)

    Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

    2017-10-01

    The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

  17. A Spectral Clustering Approach to Lagrangian Vortex Detection

    Science.gov (United States)

    Hadjighasem, Alireza; Karrasch, Daniel; Teramoto, Hiroshi; Haller, George

    2015-11-01

    One of the ubiquitous features of real-life turbulent flows is the existence and persistence of coherent vortices. Here we show that such coherent vortices can be extracted as clusters of Lagrangian trajectories. We carry out the clustering on a weighted graph, with the weights measuring pairwise distances of fluid trajectories in the extended phase space of positions and time. We then extract coherent vortices from the graph using tools from spectral graph theory. Our method locates all coherent vortices in the flow simultaneously, thereby showing high potential for automated vortex tracking. We illustrate the performance of this technique by identifying coherent Lagrangian vortices in several two- and three-dimensional flows.

  18. Spectral-clustering approach to Lagrangian vortex detection

    Science.gov (United States)

    Hadjighasem, Alireza; Karrasch, Daniel; Teramoto, Hiroshi; Haller, George

    2016-06-01

    One of the ubiquitous features of real-life turbulent flows is the existence and persistence of coherent vortices. Here we show that such coherent vortices can be extracted as clusters of Lagrangian trajectories. We carry out the clustering on a weighted graph, with the weights measuring pairwise distances of fluid trajectories in the extended phase space of positions and time. We then extract coherent vortices from the graph using tools from spectral graph theory. Our method locates all coherent vortices in the flow simultaneously, thereby showing high potential for automated vortex tracking. We illustrate the performance of this technique by identifying coherent Lagrangian vortices in several two- and three-dimensional flows.

  19. Simulation of Piezoelectric Energy Harvester Based on the Vortex Flow

    Science.gov (United States)

    Li, Meng; Wang, Haifeng; Cui, Yiliang; Sun, Kaili

    2017-10-01

    In this article, numerical research on the fluid-structure interaction between the flexible piezoelectric energy harvester (FPEH) and the Von Karman vortex street forming behind a bluff body is carried out to optimize the oscillation of FPEH to obtain more electrical energy. Using ANSYS Workbench platform, the simulation is performed. The numerical results show that the maximal deformation of the PEH is 1.7428 mm, meanwhile the maximal voltage is 4.6144 V. Besides, these numerical results generated by the ANSYS simulation are in good agreement with the experimental results.

  20. Downstream Thermal Evolution of Vortex Cores

    Science.gov (United States)

    Gómez-Barea, A.; Herrada, M. A.; Pérez-Saborid, M.; Barrero, A.

    1999-11-01

    The downstream evolution of the total temperature field in a quasi-incompressible axisymmetric vortex core has been computed. Starting at an initial station (z=0) with velocity profiles of the Burgers type and given temperature distributions, the numerical results of the evolution show that, according to experimental results, the total temperature in the near-axis region decreases substantially due to the work done by pressure and viscous forces together with the effect of both convection and conduction of heat. Depending on the values of the parameters characterizing the initial profiles and on the value of the Prandtl number, the vortex either breaks down or eventually reaches a self-similar regime. The results obtained shed light on the basic physics involved in the thermal separation phenomenon which appears inside Ranque-Hilsch vortex tubes.

  1. Optical vortex array in spatially varying lattice

    CERN Document Server

    Kapoor, Amit; Senthilkumaran, P; Joseph, Joby

    2015-01-01

    We present an experimental method based on a modified multiple beam interference approach to generate an optical vortex array arranged in a spatially varying lattice. This method involves two steps which are: numerical synthesis of a consistent phase mask by using two-dimensional integrated phase gradient calculations and experimental implementation of produced phase mask by utilizing a phase only spatial light modulator in an optical 4f Fourier filtering setup. This method enables an independent variation of the orientation and period of the vortex lattice. As working examples, we provide the experimental demonstration of various spatially variant optical vortex lattices. We further confirm the existence of optical vortices by formation of fork fringes. Such lattices may find applications in size dependent trapping, sorting, manipulation and photonic crystals.

  2. Tunable Intense High-Order Vortex Generation.

    Science.gov (United States)

    Zhang, Xiaomei; Shen, Baifei

    2017-10-01

    In 2015, we found the scheme to generate intense high-order optical vortices that carry OAM in the extreme ultraviolet region based on relativistic harmonics from the surface of a solid target. The topological charge of the harmonics scales with its order. These results have been confirmed in recent experiments. In the two incident beams case, we produced relativistic intense harmonics with expected frequency and optical vortex. When two counter-propagating LG laser pulses impinge on a solid thin foil and interact with each other, the contribution of each input pulse in producing harmonics can be distinguished with the help of angular momentum conservation of photons, which is almost impossible for harmonic generation without optical vortex. The generation of tunable, intense vortex harmonics with different photon topological charge is predicted based on the theoretical analysis and 3D PIC simulations. This work was supported by the National Natural Science Foundation of China (Grant Nos. 11374319, 11674339).

  3. Centre vortex removal restores chiral symmetry

    Science.gov (United States)

    Trewartha, Daniel; Kamleh, Waseem; Leinweber, Derek B.

    2017-12-01

    The influence of centre vortices on dynamical chiral symmetry breaking is investigated through the light hadron spectrum on the lattice. Recent studies of the quark propagator and other quantities have provided evidence that centre vortices are the fundamental objects underpinning dynamical chiral symmetry breaking in {SU}(3) gauge theory. For the first time, we use the chiral overlap fermion action to study the low-lying hadron spectrum on lattice ensembles consisting of Monte Carlo, vortex-removed, and vortex-projected gauge fields. We find that gauge field configurations consisting solely of smoothed centre vortices are capable of reproducing all the salient features of the hadron spectrum, including dynamical chiral symmetry breaking. The hadron spectrum on vortex-removed fields shows clear signals of chiral symmetry restoration at light values of the bare quark mass, while at heavy masses the spectrum is consistent with a theory of weakly interacting constituent quarks.

  4. Sphagnum moss disperses spores with vortex rings.

    Science.gov (United States)

    Whitaker, Dwight L; Edwards, Joan

    2010-07-23

    Sphagnum spores, which have low terminal velocities, are carried by turbulent wind currents to establish colonies many kilometers away. However, spores that are easily kept aloft are also rapidly decelerated in still air; thus, dispersal range depends strongly on release height. Vascular plants grow tall to lift spores into sufficient wind currents for dispersal, but nonvascular plants such as Sphagnum cannot grow sufficiently high. High-speed videos show that exploding capsules of Sphagnum generate vortex rings to efficiently carry spores high enough to be dispersed by turbulent air currents. Spores launched ballistically at similar speeds through still air would travel a few millimeters and not easily reach turbulent air. Vortex rings are used by animals; here, we report vortex rings generated by plants.

  5. Magnetic Vortex Crystals in Frustrated Mott Insulator

    Directory of Open Access Journals (Sweden)

    Y. Kamiya

    2014-02-01

    Full Text Available Quantum fluctuations become particularly relevant in highly frustrated quantum magnets and can lead to new states of matter. We provide a simple and robust scenario for inducing magnetic vortex crystals in frustrated Mott insulators. By considering a quantum paramagnet that has a gapped spectrum with six-fold degenerate low-energy modes, we study the magnetic-field-induced condensation of these modes. We use a dilute gas approximation to demonstrate that a plethora of multi-Q condensates are stabilized for different combinations of exchange interactions. This rich quantum phase diagram includes magnetic vortex crystals, which are further stabilized by symmetric exchange anisotropies. Because skyrmion and domain-wall crystals have already been predicted and experimentally observed, this novel vortex phase completes the picture of emergent crystals of topologically nontrivial spin configurations.

  6. Wavelength-versatile optical vortex lasers

    Science.gov (United States)

    Omatsu, Takashige; Miyamoto, Katsuhiko; Lee, Andrew J.

    2017-12-01

    The unique properties of optical vortex beams, in particular their spiral wavefront, have resulted in the emergence of a wide range of unique applications for this type of laser output. These applications include optical tweezing, free space optical communications, microfabrication, environmental optics, and astrophysics. However, much like the laser in its infancy, the adaptation of this type of laser output requires a diversity of wavelengths. We report on recent progress on development of optical vortex laser sources and in particular, focus on their wavelength extension, where nonlinear optical processes have been used to generate vortex laser beams with wavelengths which span the ultraviolet to infrared. We show that nonlinear optical conversion can be used to not only diversify the output wavelength of these sources, but can be used to uniquely engineer the wavefront and spatial properties of the laser output.

  7. The Effect of Organizational Support, Transformational Leadership, Personnel Empowerment, Work Engagement, Performance and Demographical Variables on the Factors of Psychological Capital

    Directory of Open Access Journals (Sweden)

    Didem Rodoplu Şahin

    2014-03-01

    Full Text Available The relation with the work and the role of managers and organizational factors are effective on psychological capital and individual performance of employees. This article investigates the impact of the work engagement, performanmce, empowerment, organizational support and transformational leadership on psychological capital using survey data.

  8. Optimisation of high-performance liquid chromatography with diode array detection using an automatic peak tracking procedure based on augmented iterative target transformation factor analysis

    NARCIS (Netherlands)

    van Zomeren, Paul; Hoogvorst, A.; Coenegracht, P.M J; de Jong, G.J.

    2004-01-01

    An automated method for the optimisation of high-performance liquid chromatography is developed. First of all, the sample of interest is analysed with various eluent compositions. All obtained data are combined into one augmented data matrix. Subsequently, augmented iterative target transformation

  9. Vortex lattice theory: A linear algebra approach

    Science.gov (United States)

    Chamoun, George C.

    Vortex lattices are prevalent in a large class of physical settings that are characterized by different mathematical models. We present a coherent and generalized Hamiltonian fluid mechanics-based formulation that reduces all vortex lattices into a classic problem in linear algebra for a non-normal matrix A. Via Singular Value Decomposition (SVD), the solution lies in the null space of the matrix (i.e., we require nullity( A) > 0) as well as the distribution of its singular values. We demonstrate that this approach provides a good model for various types of vortex lattices, and makes it possible to extract a rich amount of information on them. The contributions of this thesis can be classified into four main points. The first is asymmetric equilibria. A 'Brownian ratchet' construct was used which converged to asymmetric equilibria via a random walk scheme that utilized the smallest singular value of A. Distances between configurations and equilibria were measured using the Frobenius norm ||·||F and 2-norm ||·||2, and conclusions were made on the density of equilibria within the general configuration space. The second contribution used Shannon Entropy, which we interpret as a scalar measure of the robustness, or likelihood of lattices to occur in a physical setting. Third, an analytic model was produced for vortex street patterns on the sphere by using SVD in conjunction with expressions for the center of vorticity vector and angular velocity. Equilibrium curves within the configuration space were presented as a function of the geometry, and pole vortices were shown to have a critical role in the formation and destruction of vortex streets. The fourth contribution entailed a more complete perspective of the streamline topology of vortex streets, linking the bifurcations to critical points on the equilibrium curves.

  10. The second law analysis of natural gas behavior within a vortex tube

    Directory of Open Access Journals (Sweden)

    Kargaran Mahyar

    2013-01-01

    Full Text Available Vortex tube is a simple device without a moving part which is capable of separating hot and cold gas streams from a higher pressure inlet gas stream. The mechanism of energy separation has been investigated by several scientists and second law approach has emerged as an important tool for optimizing the vortex tube performance. Here, a thermodynamic model has been used to investigate vortex tube energy separation. Further, a method has been proposed for optimizing the vortex tube based on the rate of entropy generation obtained from experiments. Also, an experimental study has been carried out to investigate the effects of the hot tube length and cold orifice diameter on entropy generation within a vortex tube with natural gas as working fluid. A comparison has been made between air and natural gas as working fluids. The results show that the longest tube generates lowest entropy for NG. For air, it is middle tube which generates lowest entropy. Integration of entropy generation for all available cold mass fractions unveiled that an optimized value for hot tube length and cold orifice diameter is exist.

  11. Efficient creation of electron vortex beams for high resolution STEM imaging.

    Science.gov (United States)

    Béché, A; Juchtmans, R; Verbeeck, J

    2017-07-01

    The recent discovery of electron vortex beams carrying quantised angular momentum in the TEM has led to an active field of research, exploring a variety of potential applications including the possibility of mapping magnetic states at the atomic scale. A prerequisite for this is the availability of atomic sized electron vortex beams at high beam current and mode purity. In this paper we present recent progress showing that by making use of the Aharonov-Bohm effect near the tip of a long single domain ferromagnetic Nickel needle, a very efficient aperture for the production of electron vortex beams can be realised. The aperture transmits more than 99% of all electrons and provides a vortex mode purity of up to 92%. Placing this aperture in the condenser plane of a state of the art Cs corrected microscope allows us to demonstrate atomic resolution HAADF STEM images with spatial resolution better than 1 Angström, in agreement with theoretical expectations and only slightly inferior to the performance of a non-vortex probe on the same instrument. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Measurement of vortex ring characteristics during pairing in a forced subsonic air jet

    Science.gov (United States)

    Schram, C.; Riethmuller, M. L.

    2002-07-01

    The pairing of vortex rings in an acoustically excited jet is experimentally investigated. The acoustical forcing of the jet allows a series of particle image velocimetry (PIV) measurements to be performed at a frequency slightly lower than the frequency at which the vortex rings are shed in the shear layer. This technique, here called stroboscopic PIV, provides a time-resolved evolution of the velocity and vorticity fields during the threading and merging of the vortex rings, with a view to the prediction of the sound produced by this interaction. The evolution of the characteristics of the cores of the vortex rings during pairing is determined using an automated vortex detection algorithm. Three stages are distinguished in the evolution of the rings, based on the relative acceleration and deformation of their cores. The conservation of the circulation during the merging is addressed. The accuracy of the measurements is estimated, being a crucial issue for the future prediction of the sound generation based on the experimental description of the flow field.

  13. Numerical simulations of the internal flow pattern of a vortex pump compared to the Hamel-Oseen vortex

    Energy Technology Data Exchange (ETDEWEB)

    Gerlach, Angela; Preuss, Enrico; Thamsen, Paul Uwe [Institute of Fluid System Dynamics, Technische Universitaet, Berlin (Germany); Lykholt-Ustrup, Flemming [Grundfos Holding A/S, Bjerringbro (Denmark)

    2017-04-15

    We did a numerical study of the internal flow field of a vortex pump. Five operating points were considered and validated through a measured characteristic curve. The internal flow pattern of a vortex pump was analyzed and compared to the Hamel-Oseen vortex model. The calculated flow field was assessed with respect to the circumferential velocity, the vorticity and the axial velocity. Whereas the trajectories of the circumferential velocity were largely in line with the Hamel-Oseen vortex model, the opposite was true for vorticity. Only the vorticity at strong part load was in line with the predictions of the Hamel-Oseen vortex model. We therefore compared the circumferential velocity and vorticity for strong part load operation to the analytical predictions of the Hamel-Oseen vortex model. The simulated values were below the analytical values. The study therefore suggests that a vortex similar to the Hamel-Oseen vortex is only present at the strong part load operation.

  14. Theory of pairing symmetry in the vortex states

    NARCIS (Netherlands)

    Yokoyama, Takehito; Ichioka, Yukio; Yanaka, Yukio; Golubov, Alexandre Avraamovitch

    2010-01-01

    We investigate pairing symmetry in an Abrikosov vortex and vortex lattice. It is shown that the Cooper pair wave function at the center of an Abrikosov vortex with vorticity m has a different parity with respect to frequency from that in the bulk if m is an odd number, while it has the same parity

  15. Catalyzing healthcare transformation with digital health: Performance indicators and lessons learned from a Digital Health Innovation Group.

    Science.gov (United States)

    Tseng, Jocelyn; Samagh, Sonia; Fraser, Donna; Landman, Adam B

    2017-09-25

    Despite considerable investment in digital health (DH) companies and a growing DH ecosystem, there are multiple challenges to testing and implementing innovative solutions. Health systems have recognized the potential of DH and have formed DH innovation centers. However, limited information is available on DH innovation center processes, best practices, or outcomes. This case report describes a DH innovation center process that can be replicated across health systems and defines and benchmarks process indicators to assess DH innovation center performance. The Brigham and Women's Hospital's Digital Health Innovation Group (DHIG) accelerates DH innovations from idea to pilot safely and efficiently using a structured process. Fifty-four DH innovations were accelerated by the DHIG process between July 2014 and December 2016. In order to measure effectiveness of the DHIG process, key process indicators were defined as 1) number of solutions that completed each DHIG phase and 2) length of time to complete each phase. Twenty-three DH innovations progressed to pilot stage and 13 innovations were terminated after barriers to pilot implementation were identified by the DHIG process. For 4 DH solutions that executed a pilot, the average time for innovations to proceed from DHIG intake to pilot initiation was 9 months. Overall, the DHIG is a reproducible process that addresses key roadblocks in DH innovation within health systems. To our knowledge, this is the first report to describe DH innovation process indicators and results within an academic health system. Therefore, there is no published data to compare our results with the results of other DH innovation centers. Standardized data collection and indicator reporting could allow benchmark comparisons across institutions. Additional opportunities exist for the validation of DH solution effectiveness and for translational support from pilot to implementation. These are critical steps to advance DH technologies and

  16. Decoding algorithm for vortex communications receiver

    Science.gov (United States)

    Kupferman, Judy; Arnon, Shlomi

    2018-01-01

    Vortex light beams can provide a tremendous alphabet for encoding information. We derive a symbol decoding algorithm for a direct detection matrix detector vortex beam receiver using Laguerre Gauss (LG) modes, and develop a mathematical model of symbol error rate (SER) for this receiver. We compare SER as a function of signal to noise ratio (SNR) for our algorithm and for the Pearson correlation algorithm. To our knowledge, this is the first comprehensive treatment of a decoding algorithm of a matrix detector for an LG receiver.

  17. Multi-Model Ensemble Wake Vortex Prediction

    Science.gov (United States)

    Koerner, Stephan; Holzaepfel, Frank; Ahmad, Nash'at N.

    2015-01-01

    Several multi-model ensemble methods are investigated for predicting wake vortex transport and decay. This study is a joint effort between National Aeronautics and Space Administration and Deutsches Zentrum fuer Luft- und Raumfahrt to develop a multi-model ensemble capability using their wake models. An overview of different multi-model ensemble methods and their feasibility for wake applications is presented. The methods include Reliability Ensemble Averaging, Bayesian Model Averaging, and Monte Carlo Simulations. The methodologies are evaluated using data from wake vortex field experiments.

  18. Geometric phase shaping of terahertz vortex beams.

    Science.gov (United States)

    Minasyan, Amalya; Trovato, Clément; Degert, Jérôme; Freysz, Eric; Brasselet, Etienne; Abraham, Emmanuel

    2017-01-01

    We propose a topological beam-shaping strategy of terahertz (THz) beams using geometric phase elements made of space-variant birefringent slabs. Quasi-monochromatic THz vortex beams are produced and characterized both in amplitude and phase from the reconstructed real-time two-dimensional imaging of the electric field. Nonseparable superpositions of such vortex beams are also obtained and characterized by two-dimensional polarimetric analysis. These results emphasize the versatility of the spin-orbit electromagnetic toolbox to prepare on-demand structured light endowed with polarization-controlled orbital angular momentum content in the THz domain, which should find many uses in future THz technologies.

  19. Selective edge enhancement using anisotropic vortex filter.

    Science.gov (United States)

    Sharma, Manoj Kumar; Joseph, Joby; Senthilkumaran, Paramasivam

    2011-09-20

    In optical image processing, selective edge enhancement is important when it is preferable to emphasize some edges of an object more than others. We propose a new method for selective edge enhancement of amplitude objects using the anisotropic vortex phase mask by introducing anisotropy in a conventional vortex mask with the help of the sine function. The anisotropy is capable of edge enhancement in the selective region and in the required direction by changing the power and offset angle, respectively, of the sine function.

  20. Integrable Abelian vortex-like solitons

    Directory of Open Access Journals (Sweden)

    Felipe Contatto

    2017-05-01

    Full Text Available We propose a modified version of the Ginzburg–Landau energy functional admitting static solitons and determine all the Painlevé-integrable cases of its Bogomolny equations of a given class of models. Explicit solutions are determined in terms of the third Painlevé transcendents, allowing us to calculate physical quantities such as the vortex number and the vortex strength. These solutions can be interpreted as the usual Abelian-Higgs vortices on surfaces of non-constant curvature with conical singularity.

  1. Integrable Abelian vortex-like solitons

    Energy Technology Data Exchange (ETDEWEB)

    Contatto, Felipe, E-mail: felipe.contatto@damtp.cam.ac.uk [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); CAPES Foundation, Ministry of Education of Brazil, Brasília, DF 70040-020 (Brazil)

    2017-05-10

    We propose a modified version of the Ginzburg–Landau energy functional admitting static solitons and determine all the Painlevé-integrable cases of its Bogomolny equations of a given class of models. Explicit solutions are determined in terms of the third Painlevé transcendents, allowing us to calculate physical quantities such as the vortex number and the vortex strength. These solutions can be interpreted as the usual Abelian-Higgs vortices on surfaces of non-constant curvature with conical singularity.

  2. VORTEX FLOW INSIDE THE DEEP SPHERICAL DIMPLE

    Directory of Open Access Journals (Sweden)

    В. Воскобійник

    2012-04-01

    Full Text Available The results of experimental researches of the forming features of the vortex flow which is formed at the turbulentflow above of the deep spherical dimple are presented. Visualization shows that inclined asymmetric large-scale vortices are generated inside the dimple. These vortex structures are switched from one tilt in other, exciting lowfrequencyoscillations. During an evolution the asymmetric vortices are broken up above an aft wall of the dimple andthe angle of their incline and break up is increased with the growth of Reynolds number.

  3. Definition of Smart Energy City and State of the art of 6 Transform cities using Key Performance Indicators. Deliverable 1.2

    Energy Technology Data Exchange (ETDEWEB)

    Sieverts Nielsen, P.; Amer, S.B.; Halsnaes, K.

    2013-08-15

    This report summarises the work undertaken under the EU-FP7 TRANSFORM project for Work Package 1 (part 1): Becoming a Smart Energy City, state of the Art and Ambition. Part 1 starts with a clear outline of each of the participating cities. The work describes the context in terms of climate, energy assets, ambitions, targets and main possibilities in terms of energy efficiency, flows and energy production. After this first step, the work focuses on the description of what a smart energy city is (this report), what the main Key Performance Indicators (KPIs) are that should be met and how this relates to where the current cities and the living labs are. It describes at the same time the current status of city planning, energy planning tools, and existing energy data. The outline should also include information on energy production, energy flows and energy efficiency, where possible. The work will draw largely on existing Strategic Energy Action Plans, Climate Action Plans and planning documents. This report establishes a definition of smart cities, develops Key Elements, Key Performance Indicators and reports on the state of the art regarding the KPIs for the 6 Transform cities. As specified in the Transform proposal, the objective of the evaluation is to identify previous and existing initiatives as a sort of stocktaking on the way to establishing a smart city transformation pathway for each of the participating cities in the Transform project. The definition of a smart energy city and the key performance indicators will be used throughout Transform the guide the work. (Author)

  4. Vortex ring state by full-field actuator disc model

    Energy Technology Data Exchange (ETDEWEB)

    Soerensen, J.N.; Shen, W.Z.; Munduate, X. [DTU, Dept. of Energy Engineering, Lyngby (Denmark)

    1997-08-01

    One-dimensional momentum theory provides a simple analytical tool for analysing the gross flow behavior of lifting propellers and rotors. Combined with a blade-element strip-theory approach, it has for many years been the most popular model for load and performance predictions of wind turbines. The model works well at moderate and high wind velocities, but is not reliable at small wind velocities, where the expansion of the wake is large and the flow field behind the rotor dominated by turbulent mixing. This is normally referred to as the turbulent wake state or the vortex ring state. In the vortex ring state, momentum theory predicts a decrease of thrust whereas the opposite is found from experiments. The reason for the disagreement is that recirculation takes place behind the rotor with the consequence that the stream tubes past the rotor becomes effectively chocked. This represents a condition at which streamlines no longer carry fluid elements from far upstream to far downstream, hence one-dimensional momentum theory is invalid and empirical corrections have to be introduced. More sophisticated analytical or semi-analytical rotor models have been used to describe stationary flow fields for heavily loaded propellers. In recent years generalized actuator disc models have been developed, but up to now no detailed computations of the turbulent wake state or the vortex ring state have been performed. In the present work the phenomenon is simulated by direct simulation of the Navier-Stokes equations, where the influence of the rotor on the flow field is modelled simply by replacing the blades by an actuator disc with a constant normal load. (EG) 13 refs.

  5. Electromagnetic Vortex-Based Radar Imaging Using a Single Receiving Antenna: Theory and Experimental Results

    Directory of Open Access Journals (Sweden)

    Tiezhu Yuan

    2017-03-01

    Full Text Available Radar imaging based on electromagnetic vortex can achieve azimuth resolution without relative motion. The present paper investigates this imaging technique with the use of a single receiving antenna through theoretical analysis and experimental results. Compared with the use of multiple receiving antennas, the echoes from a single receiver cannot be used directly for image reconstruction using Fourier method. The reason is revealed by using the point spread function. An additional phase is compensated for each mode before imaging process based on the array parameters and the elevation of the targets. A proof-of-concept imaging system based on a circular phased array is created, and imaging experiments of corner-reflector targets are performed in an anechoic chamber. The azimuthal image is reconstructed by the use of Fourier transform and spectral estimation methods. The azimuth resolution of the two methods is analyzed and compared through experimental data. The experimental results verify the principle of azimuth resolution and the proposed phase compensation method.

  6. Low-amplitude magnetic vortex core reversal by non-linear interference between azimuthal spin waves and the vortex gyromode

    OpenAIRE

    Sproll, Markus; Noske, Matthias; Bauer, Hans; Kammerer, Matthias; Gangwar, Ajay; Dieterle, Georg; Weigand, Markus; Stoll, Hermann; Back, Christian H.; Schütz, Gisela

    2013-01-01

    We demonstrate a non-linear interference due to an active 'dual frequency' excitation of both, the sub-GHz vortex gyromode and multi-GHz magneto-static spin waves in ferromagnetic micrometer sized platelets in the vortex state. When the sub-GHz vortex gyromode is excited simultaneously a significant broadband reduction of the switching threshold for spin wave mediated vortex core reversal is observed in both, experiments and micromagnetic simulations. Consequently, the magnetic field amplitud...

  7. Quantification of Vortex Generation Due to Non-Equilibrium Electrokinetics at the Micro/Nanochannel Interface: Particle Tracking Velocimetry

    Directory of Open Access Journals (Sweden)

    Seung Jun Lee

    2016-07-01

    Full Text Available We describe a quantitative study of vortex generation due to non-equilibrium electrokinetics near a micro/nanochannel interface. The microfluidic device is comprised of a microchannel with a set of nanochannels. These perm-selective nanochannels induce flow instability and thereby produce strong vortex generation. We performed tracking visualization of fluorescent microparticles to obtain velocity fields. Particle tracking enables the calculation of an averaged velocity field and the velocity fluctuations. We characterized the effect of applied voltages and electrolyte concentrations on vortex formation. The experimental results show that an increasing voltage or decreasing concentration results in a larger vortex region and a strong velocity fluctuation. We calculate the normalized velocity fluctuation—whose meaning is comparable to turbulent intensity—and we found that it is as high as 0.12. This value is indicative of very efficient mixing, albeit with a small Reynolds number.

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

    Science.gov (United States)

    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.

  9. Diagnostics of spatial structure of vortex multiplets in a swirl flow

    Science.gov (United States)

    Naumov, I. V.; Okulov, V. L.; Sorensen, J. N.

    2010-12-01

    Results on investigation of vortex unstable breakdown are presented. The structure of vortex multiplets was visualized in a vertical cylindrical container made of transparent organic glass of the optic quality with the inner diameter of 288 mm and rotating upper lid. Visualization was performed for different heights of this cylinder. The working liquid was 80-percent water-glycerin mixture, and small air bubbles were used as the tracers. The lid was rotated with a constant angular velocity under the studied conditions, and air was accumulated in the zones of decreased pressure on axes of vortices. Visualization of flow structure for unstable swirl flows and cylinder aspect ratios from 3.2 to 5.5 allowed first identification of these regimes as multispiral breakdowns with formation of helical-like vortex duplets, triplets, and quadruplets.

  10. Level set formulation of two-dimensional Lagrangian vortex detection methods

    CERN Document Server

    Hadjighasem, Alireza

    2016-01-01

    We propose here the use of the variational level set methodology to capture Lagrangian vortex boundaries in 2D unsteady velocity fields. This method reformulates earlier approaches that seek material vortex boundaries as extremum solutions of variational problems. We demonstrate the performance of this technique for two different variational formulations built upon different notions of coherence. The first formulation uses an energy functional that penalizes the deviation of a closed material line from piecewise uniform stretching [Haller and Beron-Vera, J. Fluid Mech. 731, R4 (2013)]. The second energy function is derived for a graph-based approach to vortex boundary detection [Hadjighasem et al., Phys. Rev. E 93, 063107 (2016)]. Our level-set formulation captures an a priori unknown number of vortices simultaneously at relatively low computational cost. We illustrate the approach by identifying vortices from different coherence principles in several examples.

  11. Adaptive computations of flow around a delta wing with vortex breakdown

    Science.gov (United States)

    Modiano, David L.; Murman, Earll M.

    1993-01-01

    An adaptive unstructured mesh solution method for the three-dimensional Euler equations was used to simulate the flow around a sharp edged delta wing. Emphasis was on the breakdown of the leading edge vortex at high angle of attack. Large values of entropy, which indicate vortical regions of the flow, specified the region in which adaptation was performed. The aerodynamic normal force coefficients show excellent agreement with wind tunnel data measured by Jarrah, and demonstrate the importance of adaptation in obtaining an accurate solution. The pitching moment coefficient and the location of vortex breakdown are compared with experimental data measured by Hummel and Srinivasan, showing good agreement in cases in which vortex breakdown is located over the wing.

  12. Direct observation of the thermal demagnetization of magnetic vortex structures in nonideal magnetite recorders

    DEFF Research Database (Denmark)

    Almeida, Trevor P.; Muxworthy, Adrian R.; Kovács, András

    2016-01-01

    heating is achieved through the construction and examination of magnetic-induction maps. Stepwise demagnetization of the remanence-induced Fe3O4 particle upon heating to above the Curie temperature, performed in a similar fashion to bulk thermal demagnetization measurements, revealed that its vortex state...... remains stable under heating close to its unblocking temperature and is recovered upon cooling with the same or reversed vorticity. Hence, the PSD Fe3O4 particle exhibits thermomagnetic behavior comparable to a single-domain carrier, and thus, vortex states are considered reliable magnetic recorders...

  13. Research of power fuel low-temperature vortex combustion in industrial boiler based on numerical modelling

    Directory of Open Access Journals (Sweden)

    Orlova K.Y.

    2017-01-01

    Full Text Available The goal of the presented research is to perform numerical modelling of fuel low-temperature vortex combustion in once-through industrial steam boiler. Full size and scaled-down furnace model created with FIRE 3D software and was used for the research. All geometrical features were observed. The baseline information for the low-temperature vortex furnace process are velocity and temperature of low, upper and burner blast, air-fuel ratio, fuel consumption, coal dust size range. The obtained results are: temperature and velocity three dimensional fields, furnace gases and solid fuel ash particles concentration.

  14. The high Arctic in extreme winters: vortex, temperature, and MLS and ACE-FTS trace gas evolution

    Directory of Open Access Journals (Sweden)

    G. L. Manney

    2008-02-01

    Full Text Available The first three Arctic winters of the ACE mission represented two extremes of winter variability: Stratospheric sudden warmings (SSWs in 2004 and 2006 were among the strongest, most prolonged on record; 2005 was a record cold winter. Canadian Arctic Atmospheric Chemistry Experiment (ACE Validation Campaigns were conducted at Eureka (80° N, 86° W during each of these winters. New satellite measurements from ACE-Fourier Transform Spectrometer (ACE-FTS, Sounding of the Atmosphere using Broadband Emission Radiometry (SABER, and Aura Microwave Limb Sounder (MLS, along with meteorological analyses and Eureka lidar temperatures, are used to detail the meteorology in these winters, to demonstrate its influence on transport, and to provide a context for interpretation of ACE-FTS and validation campaign observations. During the 2004 and 2006 SSWs, the vortex broke down throughout the stratosphere, reformed quickly in the upper stratosphere, and remained weak in the middle and lower stratosphere. The stratopause reformed at very high altitude, near 75 km. ACE measurements covered both vortex and extra-vortex conditions in each winter, except in late-February through mid-March 2004 and 2006, when the strong, pole-centered vortex that reformed after the SSWs resulted in ACE sampling only inside the vortex in the middle through upper stratosphere. The 2004 and 2006 Eureka campaigns were during the recovery from the SSWs, with the redeveloping vortex over Eureka. 2005 was the coldest winter on record in the lower stratosphere, but with an early final warming in mid-March. The vortex was over Eureka at the start of the 2005 campaign, but moved away as it broke up. Disparate temperature profile structure and vortex evolution resulted in much lower (higher temperatures in the upper (lower stratosphere in 2004 and 2006 than in 2005. Satellite temperatures agree well with lidar data up to 50–60 km, and ACE-FTS, MLS and SABER show good agreement in high

  15. Simulations of a single vortex ring using an unbounded, regularized particle-mesh based vortex method

    DEFF Research Database (Denmark)

    Hejlesen, Mads Mølholm; Spietz, Henrik J.; Walther, Jens Honore

    2014-01-01

    In resent work we have developed a new FFT based Poisson solver, which uses regularized Greens functions to obtain arbitrary high order convergence to the unbounded Poisson equation. The high order Poisson solver has been implemented in an unbounded particle-mesh based vortex method which uses a re......, unbounded particle-mesh based vortex method is used to simulate the instability, transition to turbulence and eventual destruction of a single vortex ring. From the simulation data a novel method on analyzing the dynamics of the enstrophy is presented based on the alignment of the vorticity vector......-meshing of the vortex particles to ensure the convergence of the method. Furthermore, we use a re-projection of the vorticity field to include the constraint of a divergence-free stream function which is essential for the underlying Helmholtz decomposition and ensures a divergence free vorticity field. The high order...

  16. Venusian Polar Vortex reproduced in an Atmospheric General Circulation Model

    Science.gov (United States)

    Ando, Hiroki; Imamura, Takeshi; Takagi, Masahiro; Sugimoto, Norihiko; Kashimura, Hiroki

    The Venus atmosphere has a polar vortex rotating in the retrograde direction with a period of about three days. The vortex has a warm feature surrounded by a cold collar (e.g., Taylor et al. 1980; Piccioni et al. 2006). Although the Venusian polar vortex has been reported by many observations, its mechanism is still unknown. Elson (1982, 1989) examined the structure of the polar vortex by linear calculations. However, the background zonal wind assumed in the calculations was much stronger or weaker than those retrieved in the previous measurements (e.g., Peralta et al. 2008; Kouyama et al. 2012). Lee et al. (2010) and Yamamoto and Takahashi (2012) performed numerical simulations with general circulation models (GCMs) of the Venus atmosphere and obtained vertical structure in the polar region. However, the models included artificial forcing of Kelvin and/or Rossby waves. We have developed a new Venusian GCM by modifying the Atmospheric GCM For the Earth Simulator (Sugimoto et al. 2012; 2013). The basic equations of the GCM are primitive ones in the sigma coordinate on a sphere without topography. The model resolution is T42 (i.e., about 2.8 deg x 2.8 deg grids) and L60 (Deltaz is about 2 km). Rayleigh friction (sponge layer) in the upper layer (>80 km) is applied to prevent the reflection of waves, whose effect increases gradually with height. In the model, the atmosphere is dry and forced by the solar heating and Newtonian cooling. The vertical profile of the solar heating is based on Crisp (1986), and zonally averaged distribution is used. In addition diurnal component of the solar heating, which excites the diurnal and semi-diurnal tides, is also included. Newtonian cooling relaxes the temperature to the zonally uniform basic temperature which has a virtual static stability of Venus with almost neutral layers, and its coefficient is based on Crisp (1986). To prevent numerical instability, the biharmonic hyper-diffusion is included with 0.8 days of e-folding time

  17. Numerical simulation of secondary vortex chamber effect on the cooling capacity enhancement of vortex tube

    Science.gov (United States)

    Pourmahmoud, Nader; Azar, Farid Sepehrian; Hassanzadeh, Amir

    2014-09-01

    A vortex tube with additional chamber is investigated by computational fluid mechanics techniques to realize the effects of additional chamber in Ranque-Hilsch vortex tube and to understand optimal length for placing the second chamber in order to have maximum cooling effect. Results show that by increasing the distance between two chambers, both minimum cold and maximum hot temperatures increase and maximum cooling effect occurs at Z/ L = 0.047 (dimensionless distance).

  18. Instantaneous Flow Reconstruction from Particle Trajectories with Vortex-in-Cell

    NARCIS (Netherlands)

    Schneiders, J.F.G.; Scarano, F.

    2016-01-01

    The manuscripts presents the working principle of a novel technique to interpolate sparse and scattered particle tracking velocimetry (PTV) measurements onto a dense grid, by using the velocity measurements along a full particle trajectory. The method performs iteratively a vortex-in-cell simulation

  19. Sound signature of propeller tip vortex cavitation

    NARCIS (Netherlands)

    Pennings, P.C.; Westerweel, J.; Van Terwisga, T.J.C.

    2015-01-01

    The design of an efficient propeller is limited by the harmful effects of cavitation. The insuffcient understanding of the role of vortex cavitation in noise and vibration reduces the maximum effciency by a necessary safety margin. The aim in the present study is to directly relate propeller

  20. Vortex matter driven through mesoscopic channels

    Science.gov (United States)

    Kes, P. H.; Kokubo, N.; Besseling, R.

    2004-08-01

    The dynamics of vortex matter confined to mesoscopic channels has been investigated by means of mode locking experiments. When vortices are coherently driven through the potential provided by static vortices pinned in the channel edges, interference between the washboard frequency of the moving vortex lattice and the frequency of the superimposed rf-drive causes (Shapiro-like) steps in the dc- I- V curves. The position of the voltage steps uniquely determines the number of moving rows in each channel. It also shows how the frustration between row spacing and channel width behaves as a function of magnetic field. Maxima in flow stress (∼ Ic) occur at mismatch conditions. They are related to the traffic-jam-like flow impedance caused by the disorder in the edges. At higher fields, near the 2D-melting line Bm( T), the mode-locking interference characteristic for crystalline motion, strongly depends on the velocity, i.e. the applied frequency at which the vortex motion is probed. The minimum velocity at which coherent motion could be observed, diverges when the melting line is approached from below. Above the melting line interference is absent for any frequency. These observations give the first direct evidence for a dynamic phase transition of vortex matter driven through a disorder potential as predicted by Koshelev and Vinokur.

  1. Statistical behaviour of optical vortex fields

    CSIR Research Space (South Africa)

    Roux, FS

    2009-09-01

    Full Text Available vortex fields F. Stef Roux CSIR National Laser Centre, South Africa Colloquium presented at School of Physics National University of Ireland Galway, Ireland 21 September 2009 . – p.1/37 What are optical vortices? . – p.2/37 Topological charge V− = x− iy...

  2. Iterative Brinkman penalization for remeshed vortex methods

    DEFF Research Database (Denmark)

    Hejlesen, Mads Mølholm; Koumoutsakos, Petros; Leonard, Anthony

    2015-01-01

    We introduce an iterative Brinkman penalization method for the enforcement of the no-slip boundary condition in remeshed vortex methods. In the proposed method, the Brinkman penalization is applied iteratively only in the neighborhood of the body. This allows for using significantly larger time...

  3. Point vortex dynamics: A classical mathematics playground

    DEFF Research Database (Denmark)

    Aref, Hassan

    2007-01-01

    the integrability of the three-vortex problem, the interplay of relative equilibria of identical vortices and the roots of certain polynomials, addition formulas for the cotangent and the Weierstrass zeta function, projective geometry, and other topics. The hope and intent of the article is to garner further...

  4. Peculiar rotation of electron vortex beams.

    Science.gov (United States)

    Schachinger, T; Löffler, S; Stöger-Pollach, M; Schattschneider, P

    2015-11-01

    Standard electron optics predicts Larmor image rotation in the magnetic lens field of a TEM. Introducing the possibility to produce electron vortex beams with quantized orbital angular momentum brought up the question of their rotational dynamics in the presence of a magnetic field. Recently, it has been shown that electron vortex beams can be prepared as free electron Landau states showing peculiar rotational dynamics, including no and cyclotron (double-Larmor) rotation. Additionally very fast Gouy rotation of electron vortex beams has been observed. In this work a model is developed which reveals that the rotational dynamics of electron vortices are a combination of slow Larmor and fast Gouy rotations and that the Landau states naturally occur in the transition region in between the two regimes. This more general picture is confirmed by experimental data showing an extended set of peculiar rotations, including no, cyclotron, Larmor and rapid Gouy rotations all present in one single convergent electron vortex beam. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Wake Vortex Avoidance System and Method

    Science.gov (United States)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor); Knight, Howard K. (Inventor)

    2017-01-01

    A wake vortex avoidance system includes a microphone array configured to detect low frequency sounds. A signal processor determines a geometric mean coherence based on the detected low frequency sounds. A display displays wake vortices based on the determined geometric mean coherence.

  6. Superconducting vortex pinning with artificial magnetic nanostructures.

    Energy Technology Data Exchange (ETDEWEB)

    Velez, M.; Martin, J. I.; Villegas, J. E.; Hoffmann, A.; Gonzalez, E. M.; Vicent, J. L.; Schuller, I. K.; Univ. de Oviedo-CINN; Unite Mixte de Physique CNRS/Thales; Univ. Paris-Sud; Univ.Complutense de Madrid; Univ. California at San Diego

    2008-11-01

    This review is dedicated to summarizing the recent research on vortex dynamics and pinning effects in superconducting films with artificial magnetic structures. The fabrication of hybrid superconducting/magnetic systems is presented together with the wide variety of properties that arise from the interaction between the superconducting vortex lattice and the artificial magnetic nanostructures. Specifically, we review the role that the most important parameters in the vortex dynamics of films with regular array of dots play. In particular, we discuss the phenomena that appear when the symmetry of a regular dot array is distorted from regularity towards complete disorder including rectangular, asymmetric, and aperiodic arrays. The interesting phenomena that appear include vortex-lattice reconfigurations, anisotropic dynamics, channeling, and guided motion as well as ratchet effects. The different regimes are summarized in a phase diagram indicating the transitions that take place as the characteristic distances of the array are modified respect to the superconducting coherence length. Future directions are sketched out indicating the vast open area of research in this field.

  7. Vortex dynamics in nonlinear free surface flows

    Science.gov (United States)

    Curtis, Christopher W.; Kalisch, Henrik

    2017-03-01

    The two-dimensional motion of point vortices in an inviscid fluid with a free surface and an impenetrable bed is investigated. The work is based on forming a closed system of equations for surface variables and vortex positions using a variant of the Ablowitz, Fokas, and Musslimani formulation [M. J. Ablowitz, A. S. Fokas, and Z. H. Musslimani, J. Fluid Mech. 562, 313-343 (2006)] of the water-wave free-surface problem. The equations are approximated with a dealiased spectral method making use of a high-order approximation of the Dirichlet-Neumann operator and a high-order time-stepping scheme. Numerical simulations reveal that the combination of vortex motion and solid bottom boundary yields interesting dynamics not seen in the case of vortex motion in an infinitely deep fluid. In particular, strong deformations of the free surface, including non-symmetric surface profiles and regions of large energy concentration, are observed. Our simulations also uncover a rich variety of vortex trajectories including orbiting and nearly parallel patterns of motion. The dynamics of the free surface and of the point vortices are strongly influenced by the initial placement and polarity of the vortices. The method put forward here is flexible enough to handle a large number of vortices and may easily be extended to include the effects of varying bathymetry, stratification, and background shear currents.

  8. Impact of pulsations on vortex flowmeters

    NARCIS (Netherlands)

    Peters, M.C.A.M.; Bokhorst, E. van; Limpens, C.H.L.

    1998-01-01

    The impact of imposed pulsations on the output of five 3”-industrial vortex flow meters with a triangular bluff body and various type of sensors was experimentally investigated in a gas flow over a wide range of frequencies from 20 Hz to 400 Hz and amplitudes ranging from 1% to 30% rms of the

  9. On variational principles for coherent vortex structures

    NARCIS (Netherlands)

    van de Fliert, B.W.; van Groesen, Embrecht W.C.

    1993-01-01

    Different approaches are discussed of variational principles characterizing coherent vortex structures in two-dimensional flows. Turbulent flows seem to form ordered structures in the large scales of the motion and the self-organization principle predicts asymptotic states realizing an extremal

  10. Flow induced by a skewed vortex cylinder

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The velocity field induced by a skewed vortex cylinder of longitudinal and tangential vorticity is derived in this chapter by direct integration of the Biot– Savart law. The derivation steps are provided in details. The results of Castles and Durham for the skewed semi-infinite cylinder...

  11. Chemical Observations of a Polar Vortex Intrusion

    Science.gov (United States)

    Schoeberl, M. R.; Kawa, S. R.; Douglass, A. R.; McGee, T. J.; Browell, E.; Waters, J.; Livesey, N.; Read, W.; Froidevaux, L.

    2006-01-01

    An intrusion of vortex edge air in D the interior of the Arctic polar vortex was observed on the January 31,2005 flight of the NASA DC-8 aircraft. This intrusion was identified as anomalously high values of ozone by the AROTAL and DIAL lidars. Our analysis shows that this intrusion formed when a blocking feature near Iceland collapsed, allowing edge air to sweep into the vortex interior. along the DC-8 flight track also shows the intrusion in both ozone and HNO3. Polar Stratospheric Clouds (PSCs) were observed by the DIAL lidar on the DC-8. The spatial variability of the PSCs can be explained using MLS HNO3 and H2O observations and meteorological analysis temperatures. We also estimate vortex denitrification using the relationship between N2O and HNO3. Reverse domain fill back trajectory calculations are used to focus on the features in the MLS data. The trajectory results improve the agreement between lidar measured ozone and MLS ozone and also improve the agreement between the HNO3 measurements PSC locations. The back trajectory calculations allow us to compute the local denitrification rate and reduction of HCl within the filament. We estimate a denitrification rate of about lO%/day after exposure to below PSC formation temperature. Analysis of Aura MLS observations made

  12. Three-dimensional blade vortex interactions

    Science.gov (United States)

    Davoudzadeh, Farhad; Buggein, Richard C.; Shamroth, Stephen J.; Kitaplioglu, Cahit

    1991-01-01

    A three-dimensional time dependent Navier-Stokes analysis was applied to the rotor blade vortex interaction problem. The numerical procedure is an iterative implicit procedure using three point central differences to represent spatial derivatives. A series of calculations were made to determine the time steps, pseudo-time steps, iterations, artificial dissipation level, etc. required to maintain a nondissipative vortex. Results show the chosen method to have excellent non-dissipative properties provided the correct parameters are chosen. This study was used to set parameters for both two- and three-dimensional blade vortex interaction studies. The case considered was the interaction between a vortex and a NACA0012 airfoil. The results showed the detailed physics during the interaction including the pressure pulse propagating from the blade. The simulated flow physics was qualitatively similar to that experimentally observed. The BVI phenomena is the result of the buildup and violent collapse of the shock waves and local supersonic pockets on the blade surfaces. The resulting pressure pulse build-up appears to be centered at the blade leading edge.

  13. Current-vortex filaments in magnetized plasmas

    NARCIS (Netherlands)

    Bergmans, J.; Kuvshinov, B. N.; Lakhin, V. P.; Schep, T. J.; Westerhof, E.

    1999-01-01

    Current-vortex filament solutions to the two-fluid plasma equations that describe drift-Alfven waves are presented. Such filament systems are Hamiltonian. Integrable three and four filament systems are discussed in some detail. A wide variety of orbit topologies exists in the plasma case. Special

  14. An Extended Performance Comparison of Colour to Grey and Back using the Haar, Walsh, and Kekre Wavelet Transforms

    OpenAIRE

    Dr. H. B. Kekre; Dr. Sudeep D. Thepade; Adib Parkar

    2011-01-01

    The storage of colour information in a greyscale image is not a new idea. Various techniques have been proposed using different colour spaces including the standard RGB colour space, the YUV colour space, and the YCbCr colour space. This paper extends the results described in [1] and [2]. While [1] describes the storage of colour information in a greyscale image using Haar wavelets, and [2] adds a comparison with Kekre’s wavelets, this paper adds a third transform – the Walsh transform and pr...

  15. Investigate the shock focusing under a single vortex disturbance using 2D Saint-Venant equations with a shock-capturing scheme

    Science.gov (United States)

    Zhao, Jiaquan; Li, Renfu; Wu, Haiyan

    2018-02-01

    In order to characterize the flow structure and the effect of acoustic waves caused by the shock-vortex interaction on the performance of the shock focusing, the incident plane shock wave with a single disturbance vortex focusing in a parabolic cavity is simulated systematically through solving the two-dimensional, unsteady Saint-Venant equations with the two order HLL scheme of Riemann solvers. The simulations show that the dilatation effect to be dominant in the net vorticity generation, while the baroclinic effect is dominate in the absence of initial vortex disturbance. Moreover, the simulations show that the time evolution of maximum focusing pressure with initial vortex is more complicate than that without initial vortex, which has a lot of relevance with the presence of quadrupolar acoustic wave structure induced by shock-vortex interaction and its propagation in the cavity. Among shock and other disturbance parameters, the shock Mach number, vortex Mach number and the shape of parabolic reflector proved to play a critical role in the focusing of shock waves and the strength of viscous dissipation, which in turn govern the evolution of maximum focusing pressure due to the gas dynamic focus, the change in dissipation rate and the coincidence of motion disturbance vortex with aerodynamic focus point.

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

    Science.gov (United States)

    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.

  17. Some observations concerning blade-element-momentum (BEM) methods and vortex wake methods, including numerical experiments with a simple vortex model

    Energy Technology Data Exchange (ETDEWEB)

    Snel, H. [Netherlands Energy Research Foundation ECN, Renewable Energy, Wind Energy (Netherlands)

    1997-08-01

    Recently the Blade Element Momentum (BEM) method has been made more versatile. Inclusion of rotational effects on time averaged profile coefficients have improved its achievements for performance calculations in stalled flow. Time dependence as a result of turbulent inflow, pitching actions and yawed operation is now treated more correctly (although more improvement is needed) than before. It is of interest to note that adaptations in modelling of unsteady or periodic induction stem from qualitative and quantitative insights obtained from free vortex models. Free vortex methods and further into the future Navier Stokes (NS) calculations, together with wind tunnel and field experiments, can be very useful in enhancing the potential of BEM for aero-elastic response calculations. It must be kept in mind however that extreme caution must be used with free vortex methods, as will be discussed in the following chapters. A discussion of the shortcomings and the strength of BEM and of vortex wake models is given. Some ideas are presented on how BEM might be improved without too much loss of efficiency. (EG)

  18. On the evolution of vortex rings with swirl

    Energy Technology Data Exchange (ETDEWEB)

    Naitoh, Takashi, E-mail: naitoh.takashi@nitech.ac.jp [Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Okura, Nobuyuki, E-mail: ohkura@meijo-u.ac.jp [Department of Vehicle and Mechanical Engineering, Meijo University, 1-501 Shiogamaguchi Tempaku-ku, Nagoya 468-8502 (Japan); Gotoh, Toshiyuki, E-mail: gotoh.toshiyuki@nitech.ac.jp [Department of Scientific and Engineering Simulation, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kato, Yusuke [Controller Business Unit Engineering Division 1, Engineering Department 3, Denso Wave Incorporated, 1 Yoshiike Kusagi Agui-cho, Chita-gun Aichi 470-2297 (Japan)

    2014-06-15

    A laminar vortex ring with swirl, which has the meridional velocity component inside the vortex core, was experimentally generated by the brief fluid ejection from a rotating outlet. The evolution of the vortex ring was investigated with flow visualizations and particle image velocimetry measurements in order to find the influence of swirling flow in particular upon the transition to turbulence. Immediately after the formation of a vortex ring with swirl, a columnar strong vortex along the symmetric axis is observed in all cases of the present experiment. Then the characteristic fluid discharging from a vortex ring with swirl referred to as “peeling off” appears. The amount of discharging fluid due to the “peeling off” increases with the angular velocity of the rotating outlet. We conjectured that the mechanism generating the “peeling off” is related to the columnar strong vortex by close observations of the spatio-temporal development of the vorticity distribution and the cutting 3D images constructed from the successive cross sections of a vortex ring. While a laminar vortex ring without swirl may develop azimuthal waves around its circumference at some later time and the ring structure subsequently breaks, the swirling flow in a vortex ring core reduces the amplification rate of the azimuthal wavy deformation and preserved its ring structure. Then the traveling distance of a vortex ring can be extended using the swirl flow under certain conditions.

  19. The Interaction Vortex Flow Around Two Bluff Cylinders

    Directory of Open Access Journals (Sweden)

    Hirao K.

    2013-04-01

    Full Text Available In this study, the interaction vortex flow features around a pair of parallel arranged bluff cylinders were observed by visualizing water flow experiment at the range of the gap ratio G/d=0~3. It was obtained that the result of established wind tunnel test and the result of this water tank test agreed about the characteristics of vortex shedding when varying the distance of circular cylinder gap. The flow pattern and vortex shedding frequency of another type bluff cylinder (triangular and square cylinder were also investigated. As a result of the experiment, it was shown that the flow pattern of wake flow was divided into three kinds (coupled vortex streets, biased gap flow and single vortex street regardless of the cylinder section shape and cylinder size. Then, the region of the appearance of flow pattern was shown about each case. In the case where two each other independent vortex streets were formed, three typical flow patterns of vortex formation (in-phase coupled vortex streets, out-of-phase coupled vortex streets and complication coupled vortex streets were observed. It was known that three configuration of vortex formation appear intermittently and alternatively.

  20. Non-coaxial superposition of vector vortex beams.

    Science.gov (United States)

    Aadhi, A; Vaity, Pravin; Chithrabhanu, P; Reddy, Salla Gangi; Prabakar, Shashi; Singh, R P

    2016-02-10

    Vector vortex beams are classified into four types depending upon spatial variation in their polarization vector. We have generated all four of these types of vector vortex beams by using a modified polarization Sagnac interferometer with a vortex lens. Further, we have studied the non-coaxial superposition of two vector vortex beams. It is observed that the superposition of two vector vortex beams with same polarization singularity leads to a beam with another kind of polarization singularity in their interaction region. The results may be of importance in ultrahigh security of the polarization-encrypted data that utilizes vector vortex beams and multiple optical trapping with non-coaxial superposition of vector vortex beams. We verified our experimental results with theory.