Resistive Wall Instability in the NLC Main Damping Rings

International Nuclear Information System (INIS)

Wolski, Andrzej

2004-01-01

We study transverse coupled-bunch instabilities driven by the resistive-wall impedance in the NLC Main Damping Rings. We compare the growth rates of the different modes predicted by a simple theory using a simplified lattice model with the results of a detailed simulation that includes variation of the beta functions and the actual fill structure of the machine. We find that the results of the analytical calculations are in reasonable agreement with the simulations. We include a simple model of a bunch-by-bunch feedback system in the simulation to show that the instabilities can be damped by a feedback system having parameters that are realistic, and possibly conservative. The noise level on the feedback system pick-up must be low, to avoid driving random bunch-to-bunch jitter above the specified limit of 10 percent of the vertical beam size

Transient Resistive Wall Wake for Very Short Bunches

International Nuclear Information System (INIS)

Stupakov, G.; SLAC

2005-01-01

The catch up distance for the resistive wall wake in a round pipe is approximately equal to the square of the pipe radius divided by the bunch length. The standard formulae for this wake are applicable at distances much larger than the catch up distance. In this paper, we calculate the resistive wall wake at distances compared with the catch up distance assuming a constant wall conductivity

Individual domain wall resistance in submicron ferromagnetic structures.

Science.gov (United States)

Danneau, R; Warin, P; Attané, J P; Petej, I; Beigné, C; Fermon, C; Klein, O; Marty, A; Ott, F; Samson, Y; Viret, M

2002-04-15

The resistance generated by individual domain walls is measured in a FePd nanostructure. Combining transport and magnetic imaging measurements, the intrinsic domain wall resistance is quantified. It is found positive and of a magnitude consistent with that predicted by models based on spin scattering effects within the walls. This magnetoresistance at a nanometer scale allows a direct counting of the number of walls inside the nanostructure. The effect is then used to measure changes in the magnetic configuration of submicron stripes under application of a magnetic field.

Role of the plant cell wall in gravity resistance.

Science.gov (United States)

Hoson, Takayuki; Wakabayashi, Kazuyuki

2015-04-01

Gravity resistance, mechanical resistance to the gravitational force, is a principal graviresponse in plants, comparable to gravitropism. The cell wall is responsible for the final step of gravity resistance. The gravity signal increases the rigidity of the cell wall via the accumulation of its constituents, polymerization of certain matrix polysaccharides due to the suppression of breakdown, stimulation of cross-link formation, and modifications to the wall environment, in a wide range of situations from microgravity in space to hypergravity. Plants thus develop a tough body to resist the gravitational force via an increase in cell wall rigidity and the modification of growth anisotropy. The development of gravity resistance mechanisms has played an important role in the acquisition of responses to various mechanical stresses and the evolution of land plants. Copyright © 2014 Elsevier Ltd. All rights reserved.

Gas hydrate saturation from acoustic impedance and resistivity logs in the shenhu area, south china sea

Science.gov (United States)

Wang, X.; Wu, S.; Lee, M.; Guo, Y.; Yang, S.; Liang, J.

2011-01-01

During the China's first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ???10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity. ?? 2011 Elsevier Ltd.

Stability of ideal and resistive modes in cylindrical plasmas with resistive walls and plasma rotation

International Nuclear Information System (INIS)

Bondeson, A.; Xie, H.X.

1996-01-01

The stabilization of cylindrical plasmas by resistive walls combined with plasma rotation is analyzed. Perturbations with a single mode rational surface q=m/n in a finitely conducting plasma are treated by the resistive kink dispersion relation of Coppi. The possibilities for stabilization of ideal and resistive instabilities are explored systematically in different regions of parameter space. The study confirms that an ideal instability can be stabilized by a close-fitting wall and a rotation velocity of the order of resistive growth rate. However, the region in parameter space where such stabilization occurs is very small and appears to be difficult to exploit in experiments. The overall conclusion from the cylindrical plasma model is that resistive modes can readily be wall stabilized, whereas complete wall stabilization is hard to achieve for plasmas that are ideally unstable with the wall at infinity. 26 refs, 5 figs

Electrical resistivity and thermal properties of compatibilized multi-walled carbon nanotube/polypropylene composites

Directory of Open Access Journals (Sweden)

A. Szentes

2012-06-01

Full Text Available The electrical resistivity and thermal properties of multi-walled carbon nanotube/polypropylene (MWCNT/PP composites have been investigated in the presence of coupling agents applied for improving the compatibility between the nanotubes and the polymer. A novel olefin-maleic-anhydride copolymer and an olefin-maleic-anhydride copolymer based derivative have been used as compatibilizers to achieve better dispersion of MWCNTs in the polymer matrix. The composites have been produced by extrusion followed by injection moulding. They contained different amounts of MWCNTs (0.5, 2, 3 and 5 wt% and coupling agent to enhance the interactions between the carbon nanotubes and the polymer. The electrical resistivity of the composites has been investigated by impedance spectroscopy, whereas their thermal properties have been determined using a thermal analyzer operating on the basis of the periodic thermal perturbation method. Rheological properties, BET-area and adsorption-desorption isotherms have been determined. Dispersion of MWCNTs in the polymer has been studied by scanning electron microscopy (SEM.

Geometric beam coupling impedance of LHC secondary collimators

Science.gov (United States)

Frasciello, Oscar; Tomassini, Sandro; Zobov, Mikhail; Salvant, Benoit; Grudiev, Alexej; Mounet, Nicolas

2016-02-01

The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep beam instabilities under control and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are among the major impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were higher by about a factor of 2 with respect to the theoretical predictions based on the LHC impedance model up to 2012. In that model the resistive wall impedance has been considered as the dominating impedance contribution for collimators. By carefully simulating also their geometric impedance we have contributed to the update of the LHC impedance model, reaching also a better agreement between the measured and simulated betatron tune shifts. During the just ended LHC Long Shutdown I (LSI), TCS/TCT collimators were replaced by new devices embedding BPMs and TT2-111R ferrite blocks. We present here preliminary estimations of their broad-band impedance, showing that an increase of about 20% is expected in the kick factors with respect to previous collimators without BPMs.

Transverse impedance of a periodic array of cavities

Directory of Open Access Journals (Sweden)

A. V. Fedotov

1999-06-01

Full Text Available We examine the transverse impedance of a periodic array of cavities in a beam pipe at high frequency. The calculation is an extension of a previous one for the longitudinal impedance of a periodic array of azimuthally symmetric pillboxes, for which only TM modes were needed. In the present case, we must include TE modes as well. In addition, we extend the applicability of the previous calculation by including an extra term in the coupling kernel so that the results are valid for all values of the ratio of the cavity length to the period of the structure (all values of the ratio of iris thickness to structure period. In spite of the presence of TE modes, we find that the high frequency limit of the transverse impedance is simply (2/ka^{2} times the corresponding limit of the longitudinal impedance, just as it is for the resistive wall impedances, a relation which occurs frequently for azimuthally symmetric structures. Finally, we present numerical results as well as approximate expressions for the impedance per period, valid for all ratios of cavity length to structure period.

Stabilization of ideal plasma resistive wall modes in cylindrical geometry: The effect of resistive layers

International Nuclear Information System (INIS)

Finn, J.M.

1995-01-01

A cylindrical model with finite beta having an external resonant ideal magnetohydrodynamic instability has been constructed. This resonant mode has a mode rational surface, where the safety factor q equals m/n, within the plasma. In this model, the perturbed radial magnetic field for the ideal mode is nonzero between the mode rational surface and the wall, even though it must vanish at the mode rational surface. This property of the mode is in common with the toroidal external kink. Results are presented showing that in the parameter range for which this ideal mode is stable with a conducting wall but unstable with the wall at infinity, a resistive wall mode persists. However, in the presence of plasma resistivity in a resistive layer about the mode rational surface, this resistive wall mode can be stabilized by a plasma rotation frequency of order a nominal resistive instability growth rate. Furthermore, the stabilization occurs in a large gap in wall position or beta. It is also shown that for the ideal resonant mode, as well as resistive plasma modes and nonresonant ideal plasma modes, there is a maximum value of plasma rotation above which there is no stability gap. Discussions are presented suggesting that these properties may hold for the toroidal external kink. copyright 1995 American Institute of Physics

Physics of resistive wall modes

International Nuclear Information System (INIS)

Igochine, V.

2012-01-01

The advanced tokamak regime is a promising candidate for steady-state tokamak operation which is desirable for a fusion reactor. This regime is characterized by a high bootstrap current fraction and a flat or reversed safety factor profile, which leads to operation close to the pressure limit. At this limit, an external kink mode becomes unstable. This external kink is converted into the slowly growing resistive wall mode (RWM) by the presence of a conducting wall. Reduction of the growth rate allows one to act on the mode and to stabilize it. There are two main factors which determine the stability of the RWM. The first factor comes from external magnetic perturbations (error fields, resistive wall, feedback coils, etc). This part of RWM physics is the same for tokamaks and reversed field pinch configurations. The physics of this interaction is relatively well understood and based on classical electrodynamics. The second ingredient of RWM physics is the interaction of the mode with plasma flow and fast particles. These interactions are particularly important for tokamaks, which have higher plasma flow and stronger trapped particle effects. The influence of the fast particles will also be increasingly more important in ITER and DEMO which will have a large fraction of fusion born alpha particles. These interactions have kinetic origins which make the computations challenging since not only particles influence the mode, but also the mode acts on the particles. Correct prediction of the ‘plasma–RWM’ interaction is an important ingredient which has to be combined with external field's influence (resistive wall, error fields and feedback) to make reliable predictions for RWM behaviour in tokamaks. All these issues are reviewed in this paper. (special topic)

Compressible turbulent channel flow with impedance boundary conditions

Science.gov (United States)

Scalo, Carlo; Bodart, Julien; Lele, Sanjiva K.

2015-03-01

We have performed large-eddy simulations of isothermal-wall compressible turbulent channel flow with linear acoustic impedance boundary conditions (IBCs) for the wall-normal velocity component and no-slip conditions for the tangential velocity components. Three bulk Mach numbers, Mb = 0.05, 0.2, 0.5, with a fixed bulk Reynolds number, Reb = 6900, have been investigated. For each Mb, nine different combinations of IBC settings were tested, in addition to a reference case with impermeable walls, resulting in a total of 30 simulations. The adopted numerical coupling strategy allows for a spatially and temporally consistent imposition of physically realizable IBCs in a fully explicit compressible Navier-Stokes solver. The IBCs are formulated in the time domain according to Fung and Ju ["Time-domain impedance boundary conditions for computational acoustics and aeroacoustics," Int. J. Comput. Fluid Dyn. 18(6), 503-511 (2004)]. The impedance adopted is a three-parameter damped Helmholtz oscillator with resonant angular frequency, ωr, tuned to the characteristic time scale of the large energy-containing eddies. The tuning condition, which reads ωr = 2πMb (normalized with the speed of sound and channel half-width), reduces the IBCs' free parameters to two: the damping ratio, ζ, and the resistance, R, which have been varied independently with values, ζ = 0.5, 0.7, 0.9, and R = 0.01, 0.10, 1.00, for each Mb. The application of the tuned IBCs results in a drag increase up to 300% for Mb = 0.5 and R = 0.01. It is shown that for tuned IBCs, the resistance, R, acts as the inverse of the wall-permeability and that varying the damping ratio, ζ, has a secondary effect on the flow response. Typical buffer-layer turbulent structures are completely suppressed by the application of tuned IBCs. A new resonance buffer layer is established characterized by large spanwise-coherent Kelvin-Helmholtz rollers, with a well-defined streamwise wavelength λx, traveling downstream with

Cell Wall Remodeling Enzymes Modulate Fungal Cell Wall Elasticity and Osmotic Stress Resistance.

Science.gov (United States)

Ene, Iuliana V; Walker, Louise A; Schiavone, Marion; Lee, Keunsook K; Martin-Yken, Hélène; Dague, Etienne; Gow, Neil A R; Munro, Carol A; Brown, Alistair J P

2015-07-28

The fungal cell wall confers cell morphology and protection against environmental insults. For fungal pathogens, the cell wall is a key immunological modulator and an ideal therapeutic target. Yeast cell walls possess an inner matrix of interlinked β-glucan and chitin that is thought to provide tensile strength and rigidity. Yeast cells remodel their walls over time in response to environmental change, a process controlled by evolutionarily conserved stress (Hog1) and cell integrity (Mkc1, Cek1) signaling pathways. These mitogen-activated protein kinase (MAPK) pathways modulate cell wall gene expression, leading to the construction of a new, modified cell wall. We show that the cell wall is not rigid but elastic, displaying rapid structural realignments that impact survival following osmotic shock. Lactate-grown Candida albicans cells are more resistant to hyperosmotic shock than glucose-grown cells. We show that this elevated resistance is not dependent on Hog1 or Mkc1 signaling and that most cell death occurs within 10 min of osmotic shock. Sudden decreases in cell volume drive rapid increases in cell wall thickness. The elevated stress resistance of lactate-grown cells correlates with reduced cell wall elasticity, reflected in slower changes in cell volume following hyperosmotic shock. The cell wall elasticity of lactate-grown cells is increased by a triple mutation that inactivates the Crh family of cell wall cross-linking enzymes, leading to increased sensitivity to hyperosmotic shock. Overexpressing Crh family members in glucose-grown cells reduces cell wall elasticity, providing partial protection against hyperosmotic shock. These changes correlate with structural realignment of the cell wall and with the ability of cells to withstand osmotic shock. The C. albicans cell wall is the first line of defense against external insults, the site of immune recognition by the host, and an attractive target for antifungal therapy. Its tensile strength is conferred by

On fully three-dimensional resistive wall mode and feedback stabilization computations

International Nuclear Information System (INIS)

Strumberger, E.; Merkel, P.; Sempf, M.; Guenter, S.

2008-01-01

Resistive walls, located close to the plasma boundary, reduce the growth rates of external kink modes to resistive time scales. For such slowly growing resistive wall modes, the stabilization by an active feedback system becomes feasible. The fully three-dimensional stability code STARWALL, and the feedback optimization code OPTIM have been developed [P. Merkel and M. Sempf, 21st IAEA Fusion Energy Conference 2006, Chengdu, China (International Atomic Energy Agency, Vienna, 2006, paper TH/P3-8] to compute the growth rates of resistive wall modes in the presence of nonaxisymmetric, multiply connected wall structures and to model the active feedback stabilization of these modes. In order to demonstrate the capabilities of the codes and to study the effect of the toroidal mode coupling caused by multiply connected wall structures, the codes are applied to test equilibria using the resistive wall structures currently under debate for ITER [M. Shimada et al., Nucl. Fusion 47, S1 (2007)] and ASDEX Upgrade [W. Koeppendoerfer et al., Proceedings of the 16th Symposium on Fusion Technology, London, 1990 (Elsevier, Amsterdam, 1991), Vol. 1, p. 208

Respiratory impedance is correlated with airway narrowing in asthma using three-dimensional computed tomography.

Science.gov (United States)

Karayama, M; Inui, N; Mori, K; Kono, M; Hozumi, H; Suzuki, Y; Furuhashi, K; Hashimoto, D; Enomoto, N; Fujisawa, T; Nakamura, Y; Watanabe, H; Suda, T

2018-03-01

Respiratory impedance comprises the resistance and reactance of the respiratory system and can provide detailed information on respiratory function. However, details of the relationship between impedance and morphological airway changes in asthma are unknown. We aimed to evaluate the correlation between imaging-based airway changes and respiratory impedance in patients with asthma. Respiratory impedance and spirometric data were evaluated in 72 patients with asthma and 29 reference subjects. We measured the intraluminal area (Ai) and wall thickness (WT) of third- to sixth-generation bronchi using three-dimensional computed tomographic analyses, and values were adjusted by body surface area (BSA, Ai/BSA, and WT/the square root (√) of BSA). Asthma patients had significantly increased respiratory impedance, decreased Ai/BSA, and increased WT/√BSA, as was the case in those without airflow limitation as assessed by spirometry. Ai/BSA was inversely correlated with respiratory resistance at 5 Hz (R5) and 20 Hz (R20). R20 had a stronger correlation with Ai/BSA than did R5. Ai/BSA was positively correlated with forced expiratory volume in 1 second/forced vital capacity ratio, percentage predicted forced expiratory volume in 1 second, and percentage predicted mid-expiratory flow. WT/√BSA had no significant correlation with spirometry or respiratory impedance. Respiratory resistance is associated with airway narrowing. © 2018 John Wiley & Sons Ltd.

Broadband impedance calculations and single bunch instabilities estimations of of the HLS-II storage ring

Science.gov (United States)

Zhang, Qing-Kun; Wang, Lin; Li, Wei-Min; Gao, Wei-Wei

2015-12-01

The upgrade project of the Hefei Light Source storage ring is under way. In this paper, the broadband impedances of resistive wall and coated ceramic vacuum chamber are calculated using the analytic formula, and the wake fields and impedances of other designed vacuum chambers are simulated by CST code, and then a broadband impedance model is obtained. Using the theoretical formula, longitudinal and transverse single bunch instabilities are discussed. With the carefully-designed vacuum chamber, we find that the thresholds of the beam instabilities are higher than the beam current goal. Supported by Natural Science Foundation of China (11175182, 11175180)

Positional stability of field-reversed-configurations in the presence of resistive walls

Energy Technology Data Exchange (ETDEWEB)

Rath, N., E-mail: nrath@trialphanenergy.com; Onofri, M.; Barnes, D. C. [Tri Alpha Energy, P.O. Box 7010, Rancho Santa Margarita, California 92688-7010 (United States)

2016-06-15

We show that in a field-reversed-configuration, the plasma is unstable to either transverse or axial rigid displacement, but never to both. Driving forces are found to be parallel to the direction of displacement with no orthogonal components. Furthermore, we demonstrate that the properties of a resistive wall (geometry and resistivity) in the vicinity of the plasma do not affect whether the plasma is stable or unstable, but in the case of an unstable system determine the instability growth rate. Depending on the properties of the wall, the instability growth is dominated by plasma inertia (and not affected by wall resistivity) or dominated by ohmic dissipation of wall eddy currents (and thus proportional to the wall resistivity).

Impedance of finite length resistive cylinder

Directory of Open Access Journals (Sweden)

S. Krinsky

2004-11-01

Full Text Available We determine the impedance of a cylindrical metal tube (resistor of radius a, length g, and conductivity σ attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency (k≫1/a. In the equilibrium regime, ka^{2}≪g, the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity σ. In the transient regime, ka^{2}≫g, where the contribution of transition radiation arising from the discontinuity in conductivity is important, we derive an analytic expression for the impedance and compute the short-range wakefield. The analytic results are shown to agree with numerical evaluation of the impedance.

Advances In Impedance Theory

International Nuclear Information System (INIS)

Stupakov, G.

2009-01-01

We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.

Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

Science.gov (United States)

Ferraro, N. M.; Jardin, S. C.; Lao, L. L.; Shephard, M. S.; Zhang, F.

2016-05-01

Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surrounding vacuum region are included within the computational domain. This implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. This new capability is used to simulate perturbed, free-boundary non-axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear and nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically realistic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.

Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

Energy Technology Data Exchange (ETDEWEB)

Ferraro, N. M., E-mail: nferraro@pppl.gov; Lao, L. L. [General Atomics, La Jolla, California 92186 (United States); Jardin, S. C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Shephard, M. S.; Zhang, F. [Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2016-05-15

Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surrounding vacuum region are included within the computational domain. This implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. This new capability is used to simulate perturbed, free-boundary non-axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear and nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically realistic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.

Comparison between laboratory measurements, simulations, and analytical predictions of the transverse wall impedance at low frequencies

CERN Document Server

Roncarolo, F; Kroyer, T; Metral, E; Mounet, N; Salvant, B; Zotter, B

2009-01-01

The prediction of the transverse wall beam impedance at the first unstable betatron line (8 kHz) of the CERN Large Hadron Collider (LHC) is of paramount importance for understanding and controlling the related coupled-bunch instabilities. Until now only novel analytical formulas were available at this frequency. Recently, laboratory measurements and numerical simulations were performed to cross-check the analytical predictions. The experimental results based on the measurement of the variation of a probe coil inductance in the presence of (i) sample graphite plates, (ii) stand-alone LHC collimator jaws, and (iii) a full LHC collimator assembly are presented in detail. The measurement results are compared to both analytical theories and simulations. In addition, the consequences for the understanding of the LHC impedance are discussed.

COMPARISON OF SENSORS FOR RESISTIVE WALL MODE FEEDBACK CONTROL. MILESTONE No.145 ''CONTAINING PLASMA INSTABILITIES WITH METAL WALLS''

International Nuclear Information System (INIS)

STRAIT, E.J.; CHU, M.S.; GAROFALO, A.M.; LAHAYE, R.J.; OKABAYASHI, M.; REIMERDES, H.; SCOVILLE, J.T.; TURNBULL, A.D.

2002-01-01

OAK A271 COMPARISON OF SENSORS FOR RESISTIVE WALL MODE FEEDBACK CONTROL MILESTONE No.145 CONTAINING PLASMA INSTABILITIES WITH METAL WALLS. The most serious instabilities in the tokamak are those described by ideal magneto-hydrodynamic theory. These modes limit the stable operating space of the tokamak. The ideal MHD calculations predict the stable operating space of the tokamak may be approximately doubled when a perfectly conducting metal wall is placed near the plasma boundary, compared to the case with no wall (free boundary). The unstable mode distortions of the plasma column cannot bulge out through a perfectly conducting wall. However, real walls have finite conductivity and when plasmas are operated in the regime between the free boundary stability limit and the perfectly conducting wall limit, the unstable mode encountered in that case the resistive wall mode, can leak out through the metal wall, allowing the mode to keep slowly growing. The slow growth affords the possibility of feedback stabilizing this mode with external coils. DIII-D is making good progress in such feedback stabilization research and in 2002 will use an improved set of mode sensors inside the vacuum vessel and closer to the plasma surface which are expected theoretically to improve the ability to stabilize the resistive wall mode

Stabilization of the external kink and the resistive wall mode

International Nuclear Information System (INIS)

Chu, M S; Okabayashi, M

2010-01-01

The pursuit of steady-state economic production of thermonuclear fusion energy has led to research on the stabilization of the external kink and the resistive wall mode. Advances in both experiment and theory, together with improvements in diagnostics, heating and feedback methods have led to substantial and steady progress in the understanding and stabilization of these instabilities. Many of the theory and experimental techniques and results that have been developed are useful not only for the stabilization of the resistive wall mode. They can also be used to improve the general performance of fusion confinement devices. The conceptual foundations and experimental results on the stabilization of the external kink and the resistive wall mode are reviewed. (topical review)

Superconducting fault current-limiter with variable shunt impedance

Science.gov (United States)

Llambes, Juan Carlos H; Xiong, Xuming

2013-11-19

A superconducting fault current-limiter is provided, including a superconducting element configured to resistively or inductively limit a fault current, and one or more variable-impedance shunts electrically coupled in parallel with the superconducting element. The variable-impedance shunt(s) is configured to present a first impedance during a superconducting state of the superconducting element and a second impedance during a normal resistive state of the superconducting element. The superconducting element transitions from the superconducting state to the normal resistive state responsive to the fault current, and responsive thereto, the variable-impedance shunt(s) transitions from the first to the second impedance. The second impedance of the variable-impedance shunt(s) is a lower impedance than the first impedance, which facilitates current flow through the variable-impedance shunt(s) during a recovery transition of the superconducting element from the normal resistive state to the superconducting state, and thus, facilitates recovery of the superconducting element under load.

A self-consistent nonlinear theory of resistive-wall instability in a relativistic electron beam

International Nuclear Information System (INIS)

Uhm, H.S.

1994-01-01

A self-consistent nonlinear theory of resistive-wall instability is developed for a relativistic electron beam propagating through a grounded cylindrical resistive tube. The theory is based on the assumption that the frequency of the resistive-wall instability is lower than the cutoff frequency of the waveguide. The theory is concentrated on study of the beam current modulation directly related to the resistive-wall klystron, in which a relativistic electron beam is modulated at the first cavity and propagates downstream through the resistive wall. Because of the self-excitation of the space charge waves by the resistive-wall instability, a highly nonlinear current modulation of the electron beam is accomplished as the beam propagates downstream. A partial integrodifferential equation is obtained in terms of the initial energy modulation (ε), the self-field effects (h), and the resistive-wall effects (κ). Analytically investigating the partial integrodifferential equation, a scaling law of the propagation distance z m at which the maximum current modulation occurs is obtained. It is found in general that the self-field effects dominate over the resistive-wall effects at the beginning of the propagation. As the beam propagates farther downstream, the resistive-wall effects dominate. Because of a relatively large growth rate of the instability, the required tube length of the klystron is short for most applications

Active control of multiple resistive wall modes

International Nuclear Information System (INIS)

Brunsell, P. R.; Yadikin, D.; Gregoratto, D.; Paccagnella, R.; Liu, Y. Q.; Bolzonella, T.; Cecconello, M.; Drake, J. R.; Kuldkepp, M.; Manduchi, G.; Marchiori, G.; Marrelli, L.; Partin, P.; Menmuir, S.; Ortolani, S.; Rachlew, E.; Spizzo, S.; Zanca, P.

2005-01-01

Active magnetic feedback suppression of resistive wall modes is of common interest for several fusion concepts relying on close conducting walls for stabilization of ideal magnetohydrodynamic (MHD) modes. In the advanced tokamak without plasma rotation the kink mode is not completely stabilized, but rather converted into an unstable resistive wall mode (RWM) with a growth time comparable to the wall magnetic flux penetration time. The reversed field pinch (RFP) is similar to the advanced tokamak in the sense that it uses a conducting wall for kink mode stabilization. Also both configurations are susceptible to resonant field error amplification of marginally stable modes. However, the RFP has a different RWM spectrum and, in general, a range of modes is unstable. Hence, the requirement for simultaneous feedback stabilization of multiple independent RWMs arises for the RFP configuration. Recent experiments on RWM feedback stabilization, performed in the RFP device EXTRAP T2R [1], are presented. The experimental results obtained are the first demonstration of simultaneous feedback control of multiple independent RWMs [2]. Using an array of active magnetic coils, a reproducible suppression of several RWMs is achieved for the duration of the discharge, 3-5 wall times, through feedback action. An array with 64 active saddle coils at 4 poloidal times 16 toroidal positions is used. The important issues of side band generation by the active coil array and the accompanying coupling of different unstable modes through the feedback action are addressed in this study. Open loop control experiments have been carried out to quantitatively study resonant field error amplification. (Author)

Lateral resistance of piles near vertical MSE abutment walls.

Science.gov (United States)

2013-03-01

Full scale lateral load tests were performed on eight piles located at various distances behind MSE walls. The objective of the testing was to determine the effect of spacing from the wall on the lateral resistance of the piles and on the force induc...

Static resistance function for steel-plate composite (SC) walls subject to impactive loading

International Nuclear Information System (INIS)

Bruhl, Jakob C.; Varma, Amit H.; Kim, Joo Min

2015-01-01

Highlights: • An idealized static resistance function for SC walls is proposed. • The influence of design parameters on static resistance is explained. • SDOF models can accurately estimate global response of SC walls to missile impact. - Abstract: Steel-plate composite (SC) walls consist of a plain concrete core reinforced with two steel faceplates on the surfaces. Modules (consisting of steel faceplates, shear connectors and tie-bars) can be shop-fabricated and shipped to the site for erection and concrete casting, which expedites construction schedule and thus economy. SC structures have recently been used in nuclear power plant designs and are being considered for the next generation of small modular reactors. Design for impactive and impulsive loading is an important consideration for SC walls in safety-related nuclear facilities. The authors have previously developed design methods to prevent local failure (perforation) of SC walls due to missile impact. This paper presents the development of static resistance functions for use in single-degree-of-freedom (SDOF) analyses to predict the maximum displacement response of SC walls subjected to missile impact and designed to resist local failure (perforation). The static resistance function for SC walls is developed using results of numerical analyses and parametric studies conducted using benchmarked 3D finite element (FE) models. The influence of various design parameters are discussed and used to develop idealized bilinear resistance functions for SC walls with fixed edges and simply supported edges. Results from dynamic non-linear FE analysis of SC panels subjected to rigid missile impact are compared with the maximum displacements predicted by SDOF analyses using the bilinear resistance function.

Static resistance function for steel-plate composite (SC) walls subject to impactive loading

Energy Technology Data Exchange (ETDEWEB)

Bruhl, Jakob C., E-mail: jbruhl@purdue.edu; Varma, Amit H., E-mail: ahvarma@purdue.edu; Kim, Joo Min, E-mail: kim1493@purdue.edu

2015-12-15

Highlights: • An idealized static resistance function for SC walls is proposed. • The influence of design parameters on static resistance is explained. • SDOF models can accurately estimate global response of SC walls to missile impact. - Abstract: Steel-plate composite (SC) walls consist of a plain concrete core reinforced with two steel faceplates on the surfaces. Modules (consisting of steel faceplates, shear connectors and tie-bars) can be shop-fabricated and shipped to the site for erection and concrete casting, which expedites construction schedule and thus economy. SC structures have recently been used in nuclear power plant designs and are being considered for the next generation of small modular reactors. Design for impactive and impulsive loading is an important consideration for SC walls in safety-related nuclear facilities. The authors have previously developed design methods to prevent local failure (perforation) of SC walls due to missile impact. This paper presents the development of static resistance functions for use in single-degree-of-freedom (SDOF) analyses to predict the maximum displacement response of SC walls subjected to missile impact and designed to resist local failure (perforation). The static resistance function for SC walls is developed using results of numerical analyses and parametric studies conducted using benchmarked 3D finite element (FE) models. The influence of various design parameters are discussed and used to develop idealized bilinear resistance functions for SC walls with fixed edges and simply supported edges. Results from dynamic non-linear FE analysis of SC panels subjected to rigid missile impact are compared with the maximum displacements predicted by SDOF analyses using the bilinear resistance function.

Suppression of resistive wall instabilities with distributed, independently controlled, active feedback coils

International Nuclear Information System (INIS)

Cates, C.; Shilov, M.; Mauel, M. E.; Navratil, G. A.; Maurer, D.; Mukherjee, S.; Nadle, D.; Bialek, J.; Boozer, A.

2000-01-01

External kink instabilities are suppressed in a tokamak experiment by either (1) energizing a distributed array of independently controlled active feedback coils mounted outside a segmented resistive wall or (2) inserting a second segmented wall having much higher electrical conductivity. When the active feedback coils are off and the highly conducting wall is withdrawn, kink instabilities excited by plasma current gradients grow at a rate comparable to the magnetic diffusion rate of the resistive wall. (c) 2000 American Institute of Physics

Impedance Based Analysis and Design of Harmonic Resonant Controller for a Wide Range of Grid Impedance

DEFF Research Database (Denmark)

Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede

2014-01-01

This paper investigates the effect of grid impedance variation on harmonic resonant current controllers for gridconnected voltage source converters by means of impedance-based analysis. It reveals that the negative harmonic resistances tend to be derived from harmonic resonant controllers...... in the closed-loop output admittance of converter. Such negative resistances may interact with the grid impedance resulting in steady state error or unstable harmonic compensation. To deal with this problem, a design guideline for harmonic resonant controllers under a wide range of grid impedance is proposed...

Resistive Wall Mode Stability and Control in the Reversed Field Pinch

International Nuclear Information System (INIS)

Yadikin, Dmitriy

2006-03-01

Control of MHD instabilities using a conducting wall together with external magnetic fields is an important route to improved performance and reliability in fusion devices. Active control of MHD modes is of interest for both the Advanced Tokamak and the Reversed Field Pinch (RFP) configurations. A wide range of unstable, current driven MHD modes is present in the RFP. An ideally conducting wall facing the plasma can in principle provide stabilization to these modes. However, a real, resistive wall characterized by a wall field diffusion time, cannot stabilize the ideal MHD modes unless they rotate with Alfvenic velocity, which is usually not the case. With a resistive wall, the ideal modes are converted into resistive wall modes (RWM) with growth rates comparable to the inverse wall time. Resistive wall modes have been studied in the EXTRAP T2R thin shell RFP device. Growth rates have been measured and found in agreement with linear MHD stability calculations. An advanced system for active control has been developed and installed on the EXTRAP T2R device. The system includes an array of 128 active saddle coils, fully covering the torus surface. Experiments on EXTRAP T2R have for the first time demonstrated simultaneous active suppression of multiple independent RWMs. In experiments with a partial array, coupling of different modes due to the limited number of feedback coils has been observed, in agreement with theory. Different feedback strategies, such as the intelligent shell, the rotating shell, and mode control have been studied. Further, feedback operation with different types of magnetic field sensors, measuring either the radial or the toroidal field components have been compared

Electrochemical impedance-based DNA sensor using a modified single walled carbon nanotube electrode

Energy Technology Data Exchange (ETDEWEB)

Weber, Jessica E. [Department of Mechanical Engineering, University of South Florida, Tampa, FL (United States); Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, FL (United States); Pillai, Shreekumar [Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL (United States); Ram, Manoj Kumar, E-mail: mkram@usf.edu [Department of Mechanical Engineering, University of South Florida, Tampa, FL (United States); Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, FL (United States); Kumar, Ashok [Department of Mechanical Engineering, University of South Florida, Tampa, FL (United States); Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, FL (United States); Singh, Shree R. [Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL (United States)

2011-07-20

Carbon nanotubes have become promising functional materials for the development of advanced electrochemical biosensors with novel features which could promote electron-transfer with various redox active biomolecules. This paper presents the detection of Salmonella enterica serovar Typhimurium using chemically modified single walled carbon nanotubes (SWNTs) with single stranded DNA (ssDNA) on a polished glassy carbon electrode. Hybridization with the corresponding complementary ssDNA has shown a shift in the impedance studies due to a higher charge transfer in ssDNA. The developed biosensor has revealed an excellent specificity for the appropriate targeted DNA strand. The methodologies to prepare and functionalize the electrode could be adopted in the development of DNA hybridization biosensor.

Magnetic field control of 90°, 180°, and 360° domain wall resistance

Science.gov (United States)

Majidi, Roya

2012-10-01

In the present work, we have compared the resistance of the 90°, 180°, and 360° domain walls in the presence of external magnetic field. The calculations are based on the Boltzmann transport equation within the relaxation time approximation. One-dimensional Néel-type domain walls between two domains whose magnetization differs by angle of 90°, 180°, and 360° are considered. The results indicate that the resistance of the 360° DW is more considerable than that of the 90° and 180° DWs. It is also found that the domain wall resistance can be controlled by applying transverse magnetic field. Increasing the strength of the external magnetic field enhances the domain wall resistance. In providing spintronic devices based on magnetic nanomaterials, considering and controlling the effect of domain wall on resistivity are essential.

Binding of paraquat to cell walls of paraquat resistant and susceptible biotypes of Hordeum glaucum

International Nuclear Information System (INIS)

Alizadeh, H.M.; Preston, C.; Powles, S.B.

1997-01-01

Full text: Paraquat is a widely used, non-selective, light activated contact herbicide acting as a photosystem electron acceptor. Resistance to paraquat in weed species has occurred in Australia and world-wide following extensive use of this herbicide. The mechanism of resistance to paraquat in 'Hordeum glaucum' is correlated with reduced herbicide translocation and may be due to sequestration of herbicide away from its site of action by either binding to cell walls or other means. We measured paraquat binding to a cell wall fraction in resistant and susceptible biotypes of H. glaucum to determine whether differences in binding of paraquat to cell walls could explain herbicide resistance. The cell wall fraction was isolated from leaves of resistant and susceptible biotypes and incubated with 14 C-labelled paraquat. Of the total paraquat - absorbed by a cell wall preparation, about 80% remains strongly bind to the cell wall and doesn't readily exchange with solution in the absence of divalent cations. Divalent cations (Ca 2+ ,putrescine and paraquat) can competitively exchange for paraquat tightly bound to the cell wall. From kinetic experiments it seems that there are two types of binding sites in the cell wall with different affinities for paraquat. No significant differences between cell wall, characteristics of resistant and susceptible biotypes of H. glaucum have been found in any of our experiments. Therefore, increased binding of paraquat to the cell wall appears not to be a mechanism for exclusion of paraquat in resistant biotype

Anomalous feedback and negative domain wall resistance

International Nuclear Information System (INIS)

Cheng, Ran; Xiao, Di; Zhu, Jian-Gang

2016-01-01

Magnetic induction can be regarded as a negative feedback effect, where the motive-force opposes the change of magnetic flux that generates the motive-force. In artificial electromagnetics emerging from spintronics, however, this is not necessarily the case. By studying the current-induced domain wall dynamics in a cylindrical nanowire, we show that the spin motive-force exerting on electrons can either oppose or support the applied current that drives the domain wall. The switching into the anomalous feedback regime occurs when the strength of the dissipative torque β is about twice the value of the Gilbert damping constant α . The anomalous feedback manifests as a negative domain wall resistance, which has an analogy with the water turbine. (paper)

Cell wall alterations in the leaves of fusariosis-resistant and susceptible pineapple cultivars.

Science.gov (United States)

de Farias Viégas Aquije, Glória Maria; Zorzal, Poliana Belisário; Buss, David Shaun; Ventura, José Aires; Fernandes, Patricia Machado Bueno; Fernandes, Antonio Alberto Ribeiro

2010-10-01

Fusariosis, caused by the fungus Fusarium subglutinans f. sp. ananas (Syn. F. guttiforme), is one of the main phytosanitary threats to pineapple (Ananas comosus var. comosus). Identification of plant cell responses to pathogens is important in understanding the plant-pathogen relationship and establishing strategies to improve and select resistant cultivars. Studies of the structural properties and phenolic content of cell walls in resistant (Vitoria) and susceptible (Perola) pineapple cultivars, related to resistance to the fungus, were performed. The non-chlorophyll base of physiologically mature leaves was inoculated with a conidia suspension. Analyses were performed post-inoculation by light, atomic force, scanning and transmission electron microscopy, and measurement of cell wall-bound phenolic compounds. Non-inoculated leaves were used as controls to define the constitutive tissue characteristics. Analyses indicated that morphological differences, such as cell wall thickness, cicatrization process and lignification, were related to resistance to the pathogen. Atomic force microscopy indicated a considerable difference in the mechanical properties of the resistant and susceptible cultivars, with more structural integrity, associated with higher levels of cell wall-bound phenolics, found in the resistant cultivar. p-Coumaric and ferulic acids were shown to be the major phenolics bound to the cell walls and were found in higher amounts in the resistant cultivar. Leaves of the resistant cultivar had reduced fungal penetration and a faster and more effective cicatrization response compared to the susceptible cultivar.

Development of an efficient Procedure for Resist Wall Space Experiment

Science.gov (United States)

Matsumoto, Shouhei; Kumasaki, Saori; Higuchi, Sayoko; Kirihata, Kuniaki; Inoue, Yasue; Fujie, Miho; Soga, Kouichi; Wakabayashi, Kazuyuki; Hoson, Takayuki

The Resist Wall space experiment aims to examine the role of the cortical microtubule-plasma membrane-cell wall continuum in plant resistance to the gravitational force, thereby clarifying the mechanism of gravity resistance. For this purpose, we will cultivate Arabidopsis mutants defective in organization of cortical microtubules (tua6 ) or synthesis of membrane sterols (hmg1 ) as well as the wild type under microgravity and 1 g conditions in the European Modular Cultivation System on the International Space Station up to reproductive stage, and compare phenotypes on growth and development. We will also analyze cell wall properties and gene expression levels using collected materials. However, the amounts of materials collected will be severely limited, and we should develop an efficient procedure for this space experiment. In the present study, we examined the possibility of analyzing various parameters successively using the identical material. On orbit, plant materials will be fixed with RNAlater solution, kept at 4° C for several days and then frozen in a freezer at -20° C. We first examined whether the cell wall extensibility of inflorescence stems can be measured after RNAlater fixation. The gradient of the cell wall extensibility along inflorescence stems was detected in RNAlater-fixed materials as in methanol-killed ones. The sufficient amounts of RNA to analyze the gene expression were also obtained from the materials after measurement of the cell wall extensibility. Furthermore, the levels and composition of cell wall polysaccharides could be measured using the materials after extraction of RNA. These results show that we can analyze the physical and chemical properties of the cell wall as well as gene expression using the identical material obtained in the space experiments.

Cell Wall Remodeling by a Synthetic Analog Reveals Metabolic Adaptation in Vancomycin Resistant Enterococci.

Science.gov (United States)

Pidgeon, Sean E; Pires, Marcos M

2017-07-21

Drug-resistant bacterial infections threaten to overburden our healthcare system and disrupt modern medicine. A large class of potent antibiotics, including vancomycin, operate by interfering with bacterial cell wall biosynthesis. Vancomycin-resistant enterococci (VRE) evade the blockage of cell wall biosynthesis by altering cell wall precursors, rendering them drug insensitive. Herein, we reveal the phenotypic plasticity and cell wall remodeling of VRE in response to vancomycin in live bacterial cells via a metabolic probe. A synthetic cell wall analog was designed and constructed to monitor cell wall structural alterations. Our results demonstrate that the biosynthetic pathway for vancomycin-resistant precursors can be hijacked by synthetic analogs to track the kinetics of phenotype induction. In addition, we leveraged this probe to interrogate the response of VRE cells to vancomycin analogs and a series of cell wall-targeted antibiotics. Finally, we describe a proof-of-principle strategy to visually inspect drug resistance induction. Based on our findings, we anticipate that our metabolic probe will play an important role in further elucidating the interplay among the enzymes involved in the VRE biosynthetic rewiring.

Resistive wall tearing mode generated finite net electromagnetic torque in a static plasma

International Nuclear Information System (INIS)

Hao, G. Z.; Wang, A. K.; Xu, M.; Qu, H. P.; Peng, X. D.; Wang, Z. H.; Xu, J. Q.; Qiu, X. M.; Liu, Y. Q.

2014-01-01

The MARS-F code [Y. Q. Liu et al., Phys. Plasmas 7, 3681 (2000)] is applied to numerically investigate the effect of the plasma pressure on the tearing mode stability as well as the tearing mode-induced electromagnetic torque, in the presence of a resistive wall. The tearing mode with a complex eigenvalue, resulted from the favorable averaged curvature effect [A. H. Glasser et al., Phys. Fluids 18, 875 (1975)], leads to a re-distribution of the electromagnetic torque with multiple peaking in the immediate vicinity of the resistive layer. The multiple peaking is often caused by the sound wave resonances. In the presence of a resistive wall surrounding the plasma, a rotating tearing mode can generate a finite net electromagnetic torque acting on the static plasma column. Meanwhile, an equal but opposite torque is generated in the resistive wall, thus conserving the total momentum of the whole plasma-wall system. The direction of the net torque on the plasma is always opposite to the real frequency of the mode, agreeing with the analytic result by Pustovitov [Nucl. Fusion 47, 1583 (2007)]. When the wall time is close to the oscillating time of the tearing mode, the finite net torque reaches its maximum. Without wall or with an ideal wall, no net torque on the static plasma is generated by the tearing mode. However, re-distribution of the torque density in the resistive layer still occurs

The Effect of a Pulsed Magnetic Field on Domain Wall Resistance in Magnetic Nanowires

Energy Technology Data Exchange (ETDEWEB)

Majidi, R; Tehranchi, M M; Tabrizi, K Ghafoori [Department of Physics, G.C., Shahid Beheshti University, Evin, 19838-63113, Tehran (Iran, Islamic Republic of); Phirouznia, A, E-mail: Teranchi@cc.sbu.ac.ir [Department of Physics, Azarbaijan University of Tarbiat Moallem, 53714-161 Tabriz (Iran, Islamic Republic of)

2011-04-01

The effect of a pulsed magnetic field on domain wall magnetoresistance for an ideal one-dimensional magnetic nanowire with a domain wall has been investigated. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. The results indicate that the domain wall resistance increase when enhancing the magnetic field. The evaluation of local magnetization has been considered in the presence of a pulsed magnetic field. The time evaluation of the magnetization also has an effect on the domain wall resistance. The resistance depends on the contribution of the Zeeman and exchange interactions.

The Effect of a Pulsed Magnetic Field on Domain Wall Resistance in Magnetic Nanowires

International Nuclear Information System (INIS)

Majidi, R; Tehranchi, M M; Tabrizi, K Ghafoori; Phirouznia, A

2011-01-01

The effect of a pulsed magnetic field on domain wall magnetoresistance for an ideal one-dimensional magnetic nanowire with a domain wall has been investigated. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. The results indicate that the domain wall resistance increase when enhancing the magnetic field. The evaluation of local magnetization has been considered in the presence of a pulsed magnetic field. The time evaluation of the magnetization also has an effect on the domain wall resistance. The resistance depends on the contribution of the Zeeman and exchange interactions.

Free-Boundary 3D Equilibria and Resistive Wall Instabilities with Extended-MHD

Science.gov (United States)

Ferraro, N. M.

2015-11-01

The interaction of the plasma with external currents, either imposed or induced, is a critical element of a wide range of important tokamak phenomena, including resistive wall mode (RWM) stability and feedback control, island penetration and locking, and disruptions. A model of these currents may be included within the domain of extended-MHD codes in a way that preserves the self-consistency, scalability, and implicitness of their numerical methods. Such a model of the resistive wall and non-axisymmetric coils is demonstrated using the M3D-C1 code for a variety of applications, including RWMs, perturbed non-axisymmetric equilibria, and a vertical displacement event (VDE) disruption. The calculated free-boundary equilibria, which include Spitzer resistivity, rotation, and two-fluid effects, are compared to external magnetic and internal thermal measurements for several DIII-D discharges. In calculations of the perturbed equilibria in ELM suppressed discharges, the tearing response at the top of the pedestal is found to correlate with the onset of ELM suppression. Nonlinear VDE calculations, initialized using a vertically unstable DIII-D equilibrium, resolve in both space and time the currents induced in the wall and on the plasma surface, and also the currents flowing between the plasma and the wall. The relative magnitude of these contributions and the total impulse to the wall depend on the resistive wall time, although the maximum axisymmetric force on the wall over the course of the VDE is found to be essentially independent of the wall conductivity. This research was supported by US DOE contracts DE-FG02-95ER54309, DE-FC02-04ER54698 and DE-AC52-07NA27344.

J-substitution algorithm in magnetic resonance electrical impedance tomography (MREIT): phantom experiments for static resistivity images.

Science.gov (United States)

Khang, Hyun Soo; Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyoung; Kwon, Ohin; Yoon, Jeong Rock; Seo, Jin Keun

2002-06-01

Recently, a new static resistivity image reconstruction algorithm is proposed utilizing internal current density data obtained by magnetic resonance current density imaging technique. This new imaging method is called magnetic resonance electrical impedance tomography (MREIT). The derivation and performance of J-substitution algorithm in MREIT have been reported as a new accurate and high-resolution static impedance imaging technique via computer simulation methods. In this paper, we present experimental procedures, denoising techniques, and image reconstructions using a 0.3-tesla (T) experimental MREIT system and saline phantoms. MREIT using J-substitution algorithm effectively utilizes the internal current density information resolving the problem inherent in a conventional EIT, that is, the low sensitivity of boundary measurements to any changes of internal tissue resistivity values. Resistivity images of saline phantoms show an accuracy of 6.8%-47.2% and spatial resolution of 64 x 64. Both of them can be significantly improved by using an MRI system with a better signal-to-noise ratio.

Impact of acoustic impedance and flow resistance on the power output capacity of the regenerators in travelling-wave thermoacoustic engines

International Nuclear Information System (INIS)

Yu Zhibin; Jaworski, Artur J.

2010-01-01

This paper considers the role of acoustic impedance, flow resistance, configuration and geometrical dimensions of regenerators on the power produced in travelling-wave thermoacoustic engines. The effects are modelled assuming a pure travelling-wave and ideal gas, which allows defining a pair of dimensionless factors based on the 'net' acoustic power production. Based on the analysis provided, the acoustic power flow in the regenerators is investigated numerically. It is shown that impedance essentially reflects the proportion between the acoustic power produced from heat energy through the thermoacoustic processes and the acoustic power dissipated by viscous and thermal-relaxation effects in the regenerators. Viscous resistance of the regenerator mainly determines the magnitude of the volumetric velocity and then affects the magnitude of acoustic impedance. High impedance and high volumetric velocity are both required in the regenerators for high power engines. The results also show that the optimum transverse dimension of the gas passage exists, but depends on the local acoustic impedance. In principle, it is possible to obtain an optimum combination between these two parameters.

Thioridazine affects transcription of genes involved in cell wall biosynthesis in methicillin-resistant Staphylococcus aureus

DEFF Research Database (Denmark)

Bonde, Mette; Højland, Dorte Heidi; Kolmos, Hans Jørn

2011-01-01

have previously shown that the expression of some resistance genes is abolished after treatment with thioridazine and oxacillin. To further understand the mechanism underlying the reversal of resistance, we tested the expression of genes involved in antibiotic resistance and cell wall biosynthesis...... in response to thioridazine in combination with oxacillin. We observed that the oxacillin-induced expression of genes belonging to the VraSR regulon is reduced by the addition of thioridazine. The exclusion of such key factors involved in cell wall biosynthesis will most likely lead to a weakened cell wall...... reversal of resistance by thioridazine relies on decreased expression of specific genes involved in cell wall biosynthesis....

Single Mode Theory for Impedance Eduction in Large-Scale Ducts with Grazing Flow

Science.gov (United States)

Watson, Willie R.; Gerhold, Carl H.; Jones, Michael G.; June, Jason C.

2014-01-01

An impedance eduction theory for a rigid wall duct containing an acoustic liner with an unknown impedance and uniform grazing flow is presented. The unique features of the theory are: 1) non-planar waves propagate in the hard wall sections of the duct, 2) input data consist solely of complex acoustic pressures acquired on a wall adjacent to the liner, and 3) multiple higher-order modes may exist in the direction perpendicular to the liner and the opposite rigid wall. The approach is to first measure the axial propagation constant of a dominant higher-order mode in the liner sample section. This axial propagation constant is then used in conjunction with a closed-form solution to a reduced form of the convected Helmholtz equation and the wall impedance boundary condition to educe the liner impedance. The theory is validated on a conventional liner whose impedance spectrum is educed in two flow ducts with different cross sections. For the frequencies and Mach numbers of interest, no higher-order modes propagate in the hard wall sections of the smaller duct. A benchmark method is used to educe the impedance spectrum in this duct. A dominant higher-order vertical mode propagates in the larger duct for similar test conditions, and the current theory is applied to educe the impedance spectrum. Results show that when the theory is applied to data acquired in the larger duct with a dominant higher-order vertical mode, the same impedance spectra is educed as that obtained in the small duct where only the plane wave mode is present and the benchmark method is used. This result holds for each higher-order vertical mode that is considered.

Effect of modes interaction on the resistive wall mode stability

International Nuclear Information System (INIS)

Chen Longxi; Wu Bin

2013-01-01

Effects of modes interaction on the resistive wall mode (RWM) stability are studied. When considering the modes interaction effects, the linear growth rate of the most unstable (3, 1) mode decreases. After linear evolution, the RWM saturates at the nonlinear phase. The saturation can be attributed to flux piling up on the resistive wall. When some modes exist, the (3, 1) mode saturates at lower level compared with single mode evolution. Meanwhile, the magnetic energy of the (5, 2) mode increases correspondingly, but the magnetic energy saturation level of the (2, 1) mode changes weakly. (authors)

Resistive instabilities in reversed shear discharges and wall stabilization on JT-60U

International Nuclear Information System (INIS)

Takeji, S.; Tokuda, S.; Fujita, T.; Suzuki, T.; Isayama, A.; Ide, S.; Ishii, Y.; Kamada, Y.; Koide, Y.; Matsumoto, T.; Oikawa, T.; Ozeki, T.; Sakamoto, Y.

2001-01-01

Resistive instabilities and wall stabilization of ideal low toroidal mode number, n, kink modes are investigated in JT-60U reversed shear discharges. Resistive interchange modes with n=1 are found to appear in reversed shear discharges with large pressure gradient at the normalized beta, β N , of about unity or even lower. The resistive interchange modes appear as intermittent burst-like magnetohydrodynamic (MHD) activities and higher n≤3 modes are observed occasionally in higher β N regime. No clear degradation of the plasma stored energy is observed by the resistive interchange modes themselves. It is also found that resistive interchange modes can lead to major collapse owing to a coupling with tearing modes at the outer mode rational surface over the minimum safety factor. Stability analysis revealed that stability parameter of tearing modes, Δ' , at the outer mode rational surface is affected by the free-boundary condition. The result is consistent with the experimental evidence that major collapse tends to occur when plasma edge safety factor, q*, is near integer values. Stabilization of ideal low n kink modes by the JT-60U wall is demonstrated. Magnetohydrodynamic perturbations that are attributed to resistive wall modes are observed followed by major collapse in wall-stabilized discharges. (author)

Intrinsic rotation due to MHD activity in a tokamak with a resistive wall

International Nuclear Information System (INIS)

Haines, M G; Gimblett, C G; Hastie, R J

2013-01-01

MHD activity in a tokamak, in the form of waves and instabilities, generally has a preferred direction for propagation in a two-fluid plasma. When the radial component of magnetic field associated with this activity interacts with a resistive wall, momentum or angular momentum will be given to the wall. The equal and opposite reaction will be on the plasma, in particular, for ideal and resistive modes, at the singular or resonant surfaces for the various modes. In this case the torque exerted is electromagnetic. This is in contrast to other mechanisms for intrinsic or spontaneous rotation which may arise at the plasma boundary. The resistive wall is considered generally, and the thin and thick wall limits found, the latter being relevant to ITER parameters. Remarkably small radial perturbing fields of order 0.1 G could produce a torque comparable in effect to the apparent anomalous toroidal viscosity. (paper)

Resistive-wall Wake Effect in the Beam Delivery System

International Nuclear Information System (INIS)

Delayen, J.R.; Jefferson Lab; Wu, Juhao; Raubenheimer, T.O.; SLAC; Wang, Jiunn-Ming; BNL, NSLS

2005-01-01

General formulae for resistive-wall induced beam dilution are presented and then applied to the final beam delivery system of linear colliders. Criteria for the design of final beam delivery systems are discussed

Impedance and component heating

CERN Document Server

Métral, E; Mounet, N; Pieloni, T; Salvant, B

2015-01-01

The impedance is a complex function of frequency, which represents, for the plane under consideration (longitudinal, horizontal or vertical), the force integrated over the length of an element, from a “source” to a “test” wave, normalized by their charges. In general, the impedance in a given plane is a nonlinear function of the test and source transverse coordinates, but it is most of the time sufficient to consider only the first few linear terms. Impedances can influence the motion of trailing particles, in the longitudinal and in one or both transverse directions, leading to energy loss, beam instabilities, or producing undesirable secondary effects such as excessive heating of sensitive components at or near the chamber wall, called beam-induced RF heating. The LHC performance limitations linked to impedances encountered during the 2010-2012 run are reviewed and the currently expected situation during the HL-LHC era is discussed.

Esophageal acid exposure decreases intraluminal baseline impedance levels

NARCIS (Netherlands)

Kessing, Boudewijn F.; Bredenoord, Albert J.; Weijenborg, Pim W.; Hemmink, Gerrit J. M.; Loots, Clara M.; Smout, A. J. P. M.

2011-01-01

Intraluminal baseline impedance levels are determined by the conductivity of the esophageal wall and can be decreased in gastroesophageal reflux disease (GERD) patients. The aim of this study was to investigate the baseline impedance in GERD patients, on and off proton pump inhibitor (PPI), and in

Neoclassical dissipation and resistive wall modes in tokamaks

International Nuclear Information System (INIS)

Shaing, K.C.

2004-01-01

It is shown that the critical toroidal plasma flow speed that is required to stabilize the resistive wall mode in tokamaks is reduced by a factor of the order of B/B θ or of 1.265ε 3sol4 B/B θ depending on the plasma parameters when the perturbed neoclassical viscosity driven current is taken into account. Here, B is the magnetic field strength, B θ is the poloidal magnetic field strength, and ε is the inverse aspect ratio. This effect is illustrated using an existing model for the resistive wall modes by including the neoclassical dissipation in the derivation of the dispersion relation. The derivation is based on fluid equations with the plasma viscosity, calculated using kinetic equation, as the closure. The reduction of the critical toroidal speed is a consequence of the parallel (to the magnetic field B) momentum equation when neoclassical viscosity becomes important. The results are compared with experimental observations in tokamaks

Intraesophageal impedance monitoring: clinical studies

NARCIS (Netherlands)

Conchillo Armendáriz, J.M.

2007-01-01

Electrical impedance (Z) between two electrodes is the ratio between applied voltage (U) and resulting current (I). In electrical impedance monitoring the resistance to electrical flow in an alternating current circuit is measured. Multichannel esophageal monitoring can be measured by using an

Revision of Sustainable Criteria of Concrete Walls for Earthquake-Resistant Housing

Directory of Open Access Journals (Sweden)

Alcocer S.M.

2012-10-01

Full Text Available The seismic performance of low-rise housing has been noticeably inadequate during the most recent earthquakes occurred in Latin American countries. Moreover, the literature review revealed that some traditional techniques do not contribute to building sustainable housing. In the last decade, construction of concrete walls housing has become a preferred choice because of the speed of construction and availability of materials in most of these countries. Aimed at improving seismic design methods for this type of construction, an extensive analytical and experimental program was carried out. The experimental program included quasi-static and shaking-table tests of 47 walls with different height-to-length ratios and walls with openings. Variables studied were type of concrete, web steel ratio and type of web reinforcement. The paper presents and discusses the main results of the research program and evaluates the technical and environmental feasibility for using concrete walls for sustainable and earthquake-resistant housing. Performance of concrete walls housing is assessed in terms of key environmental and earthquake-resistant requirements. It was found that concrete wall housing is not only safe under earthquakes and easily adaptable to climate, but also it stimulates environmental conservation and promotes reducing the costs of construction, operation and maintenance.

Resistive and reactive changes to the impedance of intracortical microelectrodes can be mitigated with polyethylene glycol under acute in vitro and in vivo settings

Directory of Open Access Journals (Sweden)

Salah eSommakia

2014-08-01

Full Text Available The reactive response of brain tissue to implantable intracortical microelectrodes is thought to negatively affect their recordable signal quality and impedance, resulting in unreliable longitudinal performance. The relationship between the progression of the reactive tissue into a glial scar and the decline in device performance is unclear. We show that exposure to a model protein solution in vitro and acute implantation result in both resistive and capacitive changes to electrode impedance, rather than purely resistive changes. We also show that applying 4000 MW polyethylene glycol (PEG prevents impedance increases in vitro, and reduces the percent change in impedance in vivo following implantation. Our results highlight the importance of considering the contributions of non-cellular components to the decline in neural microelectrode performance, and present a proof of concept for using a simple dip-coated PEG film to modulate changes in microelectrode impedance.

Magnetic field control of 90 Degree-Sign , 180 Degree-Sign , and 360 Degree-Sign domain wall resistance

Energy Technology Data Exchange (ETDEWEB)

Majidi, Roya, E-mail: royamajidi@gmail.com [Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, 16788-15811 Tehran (Iran, Islamic Republic of)

2012-10-01

In the present work, we have compared the resistance of the 90 Degree-Sign , 180 Degree-Sign , and 360 Degree-Sign domain walls in the presence of external magnetic field. The calculations are based on the Boltzmann transport equation within the relaxation time approximation. One-dimensional Neel-type domain walls between two domains whose magnetization differs by angle of 90 Degree-Sign , 180 Degree-Sign , and 360 Degree-Sign are considered. The results indicate that the resistance of the 360 Degree-Sign DW is more considerable than that of the 90 Degree-Sign and 180 Degree-Sign DWs. It is also found that the domain wall resistance can be controlled by applying transverse magnetic field. Increasing the strength of the external magnetic field enhances the domain wall resistance. In providing spintronic devices based on magnetic nanomaterials, considering and controlling the effect of domain wall on resistivity are essential.

Resistive requirements for the vacuum wall of a tokamak fusion reactor

International Nuclear Information System (INIS)

Brooks, J.N.; Ehat, D.; Harkness, S.D.; Norem, J.; Stevens, H.; Turner, L.

1978-01-01

Most conceptual designs of tokamak power reactors have incorporated a ceramic insulator in the vacuum wall to make the wall electrically non-conducting. Such a material will have to be highly resistant to radiation damage at doses up to at least 10 MW-yr/m 2 while being compatible with a coolant and a first wall whose dimensions change due to thermal cycling and radiation damage. Thus there is considerable incentive to assess the consequences of eliminating the flux breaker from the design and having a conducting boundary instead. In this initial study the question of having a finite wall resistance has been examined in terms of its major implications on both the normal and abnormal operation of a tokamak reactor. This study has been conducted within the framework of the ANL-EPR-77 design although the results should provide some guidance for future reactors as well. The EPR design referred to is a 5 m major radius tokamak with an aspect ratio of 3.5, and with an equilibrium plasma current of 7.3 MA. The vacuum chamber is designed to accommodate a non-circular plasma with a height to width ratio of up to 1.65. The basic vacuum wall design is shown in Fig. 1. It is located about 0.4 M from the plasma boundary and has an irregular polygon shape made of sixteen sections, one per TF coil interval. Variations of this design having a range of resistance values have been used in the analysis

Impedance pattern of vaginal and vestibular mucosa in cyclic goats

Directory of Open Access Journals (Sweden)

Ivo Křivánek

2008-01-01

Full Text Available The changes of vaginal and vestibular impedance during the oestrous cycle in goats were examined. The onset of oestrus was teased with a buck once a day during the experiment. Impedance was mea­sured by a four-terminal method. The vaginal impedance was recorded under slight pressure of electrodes to the vaginal dorsal wall at the cervix. The vestibular impedance was recorded under slight pressure of electrodes to the vestibular dorsal wall 5 cm from the vulva and at the vulva. The im­pe­dan­ce was measured once a day from 4 days before the expected oestrus to 6 days after onset of oestrus. The vaginal impedance at the cervix decreased during pro-oestrus (P < 0.01 and increased du­ring oestrus (P < 0.01. The vestibular impedance 5 cm from the vulva decreased during pro-oestrus (P < 0.01 and increased after oestrus (P < 0.01. The decrease of vaginal impedance during peri-oestrus was nearly twofold in comparison with the vestibular impedance 5 cm from the vulva. No sig­ni­fi­cant decrease of the vestibular impedance at the vulva was found during the oestrous cycle. The results indicate that the vaginal impedance at the cervix and vestibular impedance 5 cm from the vulva measured by means of a four-terminal method during the oestrous cycle display cyclic changes that are closely related to the oestrous behaviour of goats.

Skin effect modifications of the Resistive Wall Mode dynamics in tokamaks

Energy Technology Data Exchange (ETDEWEB)

Villone, Fabio, E-mail: villone@unicas.it [Ass. Euratom/ENEA/CREATE, DIEI, Università di Cassino e del Lazio Meridionale, Via Di Biasio 43, 03043 Cassino, FR (Italy); Pustovitov, Vladimir D. [Institute of Tokamak Physics, National Research Centre ‘Kurchatov Institute’, Pl. Kurchatova 1, Moscow 123182 (Russian Federation)

2013-11-22

We present the first evidence of the skin-effect modification of the Resistive Wall Mode (RWM) dynamics in a tokamak. The computations are performed with the CarMa code, using its unique ability of treating volumetric 3D conducting structures. The results prove that conventional thin-wall models and codes, assuming the thin equivalent wall located on the inner side of a real (thick) wall, may fail to get accurate estimates of RWM growth rates, since the inclusion of the skin effect makes the growth rates always larger than otherwise. The difference is noticeable even for the conventional slow RWMs and becomes substantial for faster modes. Some possible equivalent thin-wall modeling approaches are also discussed.

Multibunch resistive wall instability damping with feedback

International Nuclear Information System (INIS)

Zhabitskij, V.M.; Korenev, I.L.; Yudin, L.A.

1992-01-01

The theory of multibunch transverse resistive wall instability damping with feedback is development. The system of coupling equations is obtained for description of bunched beam motion. The general solution and eigen frequencies are found. But for two bunches or multi bunches the tune splitting is found. The band of the tune splitting is calculated. The influence of the tune splitting on the damper system stability is discussed. 14 refs

Cumulative Beam Breakup due to Resistive-Wall Wake

International Nuclear Information System (INIS)

Wang, J.-M.

2004-01-01

The cumulative beam breakup problem excited by the resistive-wall wake is formulated. An approximate analytic method of finding the asymptotic behavior for the transverse bunch displacement is developed and solved. Comparison between the asymptotic analytical expression and the direct numerical solution is presented. Good agreement is found. The criterion of using the asymptotic analytical expression is discussed

Gravity resistance, another graviresponse in plants - role of microtubule-membrane-cell wall continuum

Science.gov (United States)

Hoson, T.; Saito, Y.; Usui, S.; Soga, K.; Wakabayashi, K.

Resistance to the gravitational force has been a serious problem for plants to survive on land, after they first went ashore more than 400 million years ago. Thus, gravity resistance is the principal graviresponse in plants comparable to gravitropism. Nevertheless, only limited information has been obtained for this second gravity response. We have examined the mechanism of gravity resistance using hypergravity conditions produced by centrifugation. The results led a hypothesis on the mechanism of plant resistance to the gravitational force that the plant constructs a tough body by increasing the cell wall rigidity, which are brought about by modification of the cell wall metabolism and cell wall environment, especially pH. The hypothesis was further supported by space experiments during the Space Shuttle STS-95 mission. On the other hand, we have shown that gravity signal may be perceived by mechanoreceptors (mechanosensitive ion channels) on the plasma membrane and amyloplast sedimentation in statocytes is not involved in gravity resistance. Moreover, hypergravity treatment increased the expression levels of genes encoding alpha-tubulin, a component of microtubules and 3-hydroxy-3-methylglutaryl-Coenzyme A reductase (HMGR), which catalyzes a reaction producing mevalonic acid, a key precursor of terpenoids such as membrane sterols. The expression of HMGR and alpha- and beta-tubulin genes increased within several hours after hypergravity treatment, depending on the magnitude of gravity. The determination of levels of gene products as well as the analysis with knockout mutants of these genes by T-DNA insertions in Arabidopsis supports the involvement of both membrane sterols and microtubules in gravity resistance. These results suggest that structural or physiological continuum of microtubule-cell membrane-cell wall is responsible for plant resistance to the gravitational force.

FDTD modeling of thin impedance sheets

Science.gov (United States)

Luebbers, Raymond J.; Kunz, Karl S.

1991-01-01

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

Experimental studies of tearing mode and resistive wall mode dynamics in the reversed field pinch configuration

International Nuclear Information System (INIS)

Malmberg, Jenny-Ann

2003-06-01

It is relatively straightforward to establish equilibrium in magnetically confined plasmas, but the plasma is frequently susceptible to a variety of instabilities that are driven by the free energy in the magnetic field or in the pressure gradient. These unstable modes exhibit effects that affect the particle, momentum and heat confinement properties of the configuration. Studies of the dynamics of several of the most important modes are the subject of this thesis. The studies are carried out on plasmas in the reversed field pinch (RFP) configuration. One phenomenon commonly observed in RFPs is mode wall locking. The localized nature of these phase- and wall locked structures results in localized power loads on the wall which are detrimental for confinement. A detailed study of the wall locked mode phenomenon is performed based on magnetic measurements from three RFP devices. The two possible mechanisms for wall locking are investigated. Locking as a result of tearing modes interacting with a static field error and locking due to the presence of a non-ideal boundary. The characteristics of the wall locked mode are qualitatively similar in a device with a conducting shell system (TPE-RX) compared to a device with a resistive shell (Extrap T2). A theoretical model is used for evaluating the threshold values for wall locking due to eddy currents in the vacuum vessel in these devices. A good correlation with experiment is observed for the conducting shell device. The possibility of successfully sustaining discharges in a resistive shell RFP is introduced in the recently rebuilt device Extrap T2R. Fast spontaneous mode rotation is observed, resulting in low magnetic fluctuations, low loop voltage and improved confinement. Wall locking is rarely observed. The low tearing mode amplitudes allow for the theoretically predicted internal non-resonant on-axis resistive wall modes to be observed. These modes have not previously been distinguished due to the formation of wall

Lung and chest wall impedances in the dog: effects of frequency and tidal volume.

Science.gov (United States)

Barnas, G M; Stamenović, D; Lutchen, K R; Mackenzie, C F

1992-01-01

Dependences of the mechanical properties of the respiratory system on frequency (f) and tidal volume (VT) in the normal ranges of breathing are not clear. We measured, simultaneously and in vivo, resistance and elastance of the total respiratory system (Rrs and Ers), lungs (RL and EL), and chest wall (Rcw and Ecw) of five healthy anesthetized paralyzed dogs during sinusoidal volume oscillations at the trachea (50-300 ml, 0.2-2 Hz) delivered at a constant mean lung volume. Each dog showed the same f and VT dependences. The Ers and Ecw increased with increasing f to 1 Hz and decreased with increasing VT up to 200 ml. Although EL increased slightly with increasing f, it was independent of VT. The Rcw decreased from 0.2 to 2 Hz at all VT and decreased with increasing VT. Although the RL decreased from 0.2 to 0.6 Hz and was independent of VT, at higher f RL tended to increase with increasing f and VT (i.e., as peak flow increased). Finally, the f and VT dependences of Rrs were similar to those of Rcw below 0.6 Hz but mirrored RL at higher f. These data capture the competing influences of airflow nonlinearities vs. tissue nonlinearities on f and VT dependence of the lung, chest wall, and total respiratory system. More specifically, we conclude that 1) VT dependences in Ers and Rrs below 0.6 Hz are due to nonlinearities in chest wall properties, 2) above 0.6 Hz, the flow dependence of airways resistance dominates RL and Rrs, and 3) lung tissue behavior is linear in the normal range of breathing.

Characterizing aging effects of lithium ion batteries by impedance spectroscopy

International Nuclear Information System (INIS)

Troeltzsch, Uwe; Kanoun, Olfa; Traenkler, Hans-Rolf

2006-01-01

Impedance spectroscopy is one of the most promising methods for characterizing aging effects of portable secondary batteries online because it provides information about different aging mechanisms. However, application of impedance spectroscopy 'in the field' has some higher requirements than for laboratory experiments. It requires a fast impedance measurement process, an accurate model applicable with several batteries and a robust method for model parameter estimation. In this paper, we present a method measuring impedance at different frequencies simultaneously. We propose to use a composite electrode model, capable to describe porous composite electrode materials. A hybrid method for parameter estimation based on a combination of evolution strategy and Levenberg-Marquardt method allowed a robust and fast parameter calculation. Based on this approach, an experimental investigation of aging effects of a lithium ion battery was carried out. After 230 discharge/charge cycles, the battery showed a 14% decreased capacity. Modeling results show that series resistance, charge transfer resistance and Warburg coefficient changed thereby their values by approximately 60%. A single frequency impedance measurement, usually carried out at 1 kHz, delivers only information about series resistance. Impedance spectroscopy allows additionally the estimation of charge transfer resistance and Warburg coefficient. This fact and the high sensitivity of model parameters to capacity change prove that impedance spectroscopy together with an accurate modeling deliver information that significantly improve characterization of aging effects

Characterizing aging effects of lithium ion batteries by impedance spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Troeltzsch, Uwe [University of the Bundeswehr Munich Institute for Measurement and Automation, 85579 Neubiberg (Germany)]. E-mail: uwe.troeltzsch@unibw-muenchen.de; Kanoun, Olfa [University of the Bundeswehr Munich Institute for Measurement and Automation, 85579 Neubiberg (Germany); Traenkler, Hans-Rolf [University of the Bundeswehr Munich Institute for Measurement and Automation, 85579 Neubiberg (Germany)

2006-01-20

Impedance spectroscopy is one of the most promising methods for characterizing aging effects of portable secondary batteries online because it provides information about different aging mechanisms. However, application of impedance spectroscopy 'in the field' has some higher requirements than for laboratory experiments. It requires a fast impedance measurement process, an accurate model applicable with several batteries and a robust method for model parameter estimation. In this paper, we present a method measuring impedance at different frequencies simultaneously. We propose to use a composite electrode model, capable to describe porous composite electrode materials. A hybrid method for parameter estimation based on a combination of evolution strategy and Levenberg-Marquardt method allowed a robust and fast parameter calculation. Based on this approach, an experimental investigation of aging effects of a lithium ion battery was carried out. After 230 discharge/charge cycles, the battery showed a 14% decreased capacity. Modeling results show that series resistance, charge transfer resistance and Warburg coefficient changed thereby their values by approximately 60%. A single frequency impedance measurement, usually carried out at 1 kHz, delivers only information about series resistance. Impedance spectroscopy allows additionally the estimation of charge transfer resistance and Warburg coefficient. This fact and the high sensitivity of model parameters to capacity change prove that impedance spectroscopy together with an accurate modeling deliver information that significantly improve characterization of aging effects.

Non-invasive determination of absolute lung resistivity in adults using electrical impedance tomography

International Nuclear Information System (INIS)

Zhang, Jie; Patterson, Robert

2010-01-01

Lung resistivity is a physiological parameter that describes the electrical characteristics of the lungs. Lung composition changes due to changes in the lung tissues, fluid and air volume. Various diseases that can cause a change in lung composition may be monitored by measuring lung resistivity. Currently, there is no accepted non-invasive method to measure lung resistivity. In this study, we presented a method and framework to non-invasively determine lung resistivity using electrical impedance tomography (EIT). By comparing actual measurements from subjects with data from a 3D human thorax model, an EIT image can be reconstructed to show a resistivity difference between the model and the subject. By adjusting the lung resistivity in the model, the resistivity difference in the lung regions can be reduced to near zero. This resistivity value then is the estimation of the lung resistivity of the subject. Using the proposed method, the lung resistivities of four normal adult males (43 ± 13 years, 78 ± 10 kg) in the supine position at air volumes starting at functional residual capacity (FRC—end expiration) and increasing in 0.5 l steps to 1.5 l were studied. The averaged lung resistivity changes 12.59%, from 1406 Ω cm to 1583 Ω cm, following the inspiration of 1.5 l air from FRC. The coefficients of variation (CV) of precision for the four subjects are less than 10%. The experiment was repeated five times at each air volume on a subject to test the reproducibility. The CVs are less than 3%. The results show that it is feasible to determine absolute lung resistivity using an EIT-based method

Non-invasive determination of absolute lung resistivity in adults using electrical impedance tomography.

Science.gov (United States)

Zhang, Jie; Patterson, Robert

2010-08-01

Lung resistivity is a physiological parameter that describes the electrical characteristics of the lungs. Lung composition changes due to changes in the lung tissues, fluid and air volume. Various diseases that can cause a change in lung composition may be monitored by measuring lung resistivity. Currently, there is no accepted non-invasive method to measure lung resistivity. In this study, we presented a method and framework to non-invasively determine lung resistivity using electrical impedance tomography (EIT). By comparing actual measurements from subjects with data from a 3D human thorax model, an EIT image can be reconstructed to show a resistivity difference between the model and the subject. By adjusting the lung resistivity in the model, the resistivity difference in the lung regions can be reduced to near zero. This resistivity value then is the estimation of the lung resistivity of the subject. Using the proposed method, the lung resistivities of four normal adult males (43 +/- 13 years, 78 +/- 10 kg) in the supine position at air volumes starting at functional residual capacity (FRC--end expiration) and increasing in 0.5 l steps to 1.5 l were studied. The averaged lung resistivity changes 12.59%, from 1406 Omega cm to 1583 Omega cm, following the inspiration of 1.5 l air from FRC. The coefficients of variation (CV) of precision for the four subjects are less than 10%. The experiment was repeated five times at each air volume on a subject to test the reproducibility. The CVs are less than 3%. The results show that it is feasible to determine absolute lung resistivity using an EIT-based method.

Measurement of Resistive Wall Mode stability in rotating high beta plasmas

International Nuclear Information System (INIS)

Reimerdes, H.; Bialek, J.; Garofalo, A.M.; Navratil, G.A.; Chance, M.S.; Menard, J.E.; Okabayashi, M.; Takahashi, H.; Chu, M.S.; Gohil, P.; Jackson, G.L.; Jensen, T.H.; La Haye, R.J.; Scoville, J.T.; Strait, E.J.; Jayakumar, R.J.; Liu, Y.Q.

2005-01-01

Toroidal plasma rotation in the order of a few percent of the Alfven velocity can stabilize the resistive wall mode and extend the operating regime of tokamaks from the conventional, ideal MHD no-wall limit up to the ideal MHD ideal wall limit. The stabilizing effect has been measured passively by measuring the critical plasma rotation required for stability and actively by probing the plasma with externally applied resonant magnetic fields. These measurements are compared to predictions of rotational stabilization of the sound wave damping and of the kinetic damping model using the MARS code. (author)

Anhydrobiosis in yeast: cell wall mannoproteins are important for yeast Saccharomyces cerevisiae resistance to dehydration.

Science.gov (United States)

Borovikova, Diana; Teparić, Renata; Mrša, Vladimir; Rapoport, Alexander

2016-08-01

The state of anhydrobiosis is linked with the reversible delay of metabolism as a result of strong dehydration of cells, and is widely distributed in nature. A number of factors responsible for the maintenance of organisms' viability in these conditions have been revealed. This study was directed to understanding how changes in cell wall structure may influence the resistance of yeasts to dehydration-rehydration. Mutants lacking various cell wall mannoproteins were tested to address this issue. It was revealed that mutants lacking proteins belonging to two structurally and functionally unrelated groups (proteins non-covalently attached to the cell wall, and Pir proteins) possessed significantly lower cell resistance to dehydration-rehydration than the mother wild-type strain. At the same time, the absence of the GPI-anchored cell wall protein Ccw12 unexpectedly resulted in an increase of cell resistance to this treatment; this phenomenon is explained by the compensatory synthesis of chitin. The results clearly indicate that the cell wall structure/composition relates to parameters strongly influencing yeast viability during the processes of dehydration-rehydration, and that damage to cell wall proteins during yeast desiccation can be an important factor leading to cell death. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Local impedance measurement of an electrode/single-pentacene-grain interface by frequency-modulation scanning impedance microscopy

Energy Technology Data Exchange (ETDEWEB)

Kimura, Tomoharu; Yamada, Hirofumi, E-mail: h-yamada@kuee.kyoto-u.ac.jp [Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan); Kobayashi, Kei [Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan); The Hakubi Center for Advanced Research, Kyoto University, Kyoto 615-8520 (Japan)

2015-08-07

The device performances of organic thin film transistors are often limited by the metal–organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance of a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.

A Novel Grid Impedance Estimation Technique based on Adaptive Virtual Resistance Control Loop Applied to Distributed Generation Inverters

DEFF Research Database (Denmark)

Ghzaiel, Walid; Jebali-Ben Ghorbal, Manel; Slama-Belkhodja, Ilhem

2013-01-01

and to take the decision of either keep the DG connected, or disconnect it from the utility grid. The proposed method is based on a fast and easy grid fault detection method. A virtual damping resistance is used to drive the system to the resonance in order to extract the grid impedance parameters, both...... the power quality and even damage some sensitive loads connected at the point of the common coupling (PCC). This paper presents detection-estimation method of the grid impedance variation. This estimation tehnique aims to improve the dynamic of the distributed generation (DG) interfacing inverter control...

Application of Vertical Electrodes in Microfluidic Channels for Impedance Analysis

Directory of Open Access Journals (Sweden)

Qiang Li

2016-05-01

Full Text Available This paper presents a microfluidic device with electroplated vertical electrodes in the side walls for impedance measurement. Based on the proposed device, the impedance of NaCl solutions with different concentrations and polystyrene microspheres with different sizes was measured and analyzed. The electroplating and SU-8-PDMS (SU-8-poly(dimethylsiloxane bonding technologies were firstly integrated for the fabrication of the proposed microfluidic device, resulting in a tightly three-dimensional structure for practical application. The magnitude of impedance of the tested solutions in the frequency range of 1 Hz to 100 kHz was analyzed by the Zennium electrochemical workstation. The results show that the newly designed microfluidic device has potential for impedance analysis with the advantages of ease of fabrication and the integration of 3D electrodes in the side walls. The newly designed impedance sensor can distinguish different concentrations of polystyrene microspheres and may have potential for cell counting in biological areas. By integrating with other techniques such as dielectrophoresis (DEP and biological recognition technology, the proposed device may have potential for the assay to identify foodborne pathogen bacteria.

The utilization of brick walls for resisting earthquake in building technology

Science.gov (United States)

Tarigan, J.; Benedicta, C.

2018-03-01

Many structures in Indonesia use reinforced concrete frames with brick walls as their infill. Commonly, the engineers consider brick walls as the partitions and count them as the non-structural elements in the structure design. However, brick walls are capable of resisting earthquake by yielding high stiffness to the structure in case the brick walls are integrated well with the frames. It will reduce the non-structural destructions that happen to structures which is one of the most frequently impacts in the earthquake. This paper will take the effects of applying brick walls as the structural elements up by comparing it with the structure using brick walls as the partitions. The modeling of the brick walls uses the equivalent spectrum method meanwhile the seismic analysis uses the respon spectrum method. The utilization of brick walls can cause the decrement of the natural period to 42%. It also reduce the structure displacements to 53% in X-direction and 67% in Y-direction and the story drifts to 57% in X-direction and 71% in Y-direction. Otherwise, it causes the increment of the base shear only up to 3% in X-direction and 7% in Y-direction.

Multi-bunch effect of resistive wall in the Beam Delivery System of the Compact Linear Collider

CERN Document Server

Mutzner, R; Rumolo, G; Tomas, R; Pieloni, T

2010-01-01

Wake fields in the CLIC Beam Delivery System (BDS) can cause severe single or multi-bunch effects leading to luminosity loss. The main contributors in the BDS are geometric and resistive wall wake fields of the collimators and resistive wall wakes of the beam pipe. The present work focuses only on the multi-bunch effects from resistive wall. Using particle tracking with wake fields through the BDS, we have established the aperture radius, above which the effect of the wake fields becomes negligible. Our simulations were later extended to include a realistic aperture model along the BDS as well as the collimators. The two cases of 3 TeV and 500 GeV have been examined.

Phonon impedance matching: minimizing interfacial thermal resistance of thin films

Science.gov (United States)

Polanco, Carlos; Zhang, Jingjie; Ghosh, Avik

2014-03-01

The challenge to minimize interfacial thermal resistance is to allow a broad band spectrum of phonons, with non-linear dispersion and well defined translational and rotational symmetries, to cross the interface. We explain how to minimize this resistance using a frequency dependent broadening matrix that generalizes the notion of acoustic impedance to the whole phonon spectrum including symmetries. We show how to ``match'' two given materials by joining them with a single atomic layer, with a multilayer material and with a graded superlattice. Atomic layer ``matching'' requires a layer with a mass close to the arithmetic mean (or spring constant close to the harmonic mean) to favor high frequency phonon transmission. For multilayer ``matching,'' we want a material with a broadening close to the geometric mean to maximize transmission peaks. For graded superlattices, a continuous sequence of geometric means translates to an exponentially varying broadening that generates a wide-band antireflection coating for both the coherent and incoherent limits. Our results are supported by ``first principles'' calculations of thermal conductance for GaAs / Gax Al1 - x As / AlAs thin films using the Non-Equilibrium Greens Function formalism coupled with Density Functional Perturbation Theory. NSF-CAREER (QMHP 1028883), NSF-IDR (CBET 1134311), XSEDE.

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa - their role in the development of resistance.

Science.gov (United States)

Dhar, Supurna; Kumari, Hansi; Balasubramanian, Deepak; Mathee, Kalai

2018-01-01

The bacterial cell-wall that forms a protective layer over the inner membrane is called the murein sacculus - a tightly cross-linked peptidoglycan mesh unique to bacteria. Cell-wall synthesis and recycling are critical cellular processes essential for cell growth, elongation and division. Both de novo synthesis and recycling involve an array of enzymes across all cellular compartments, namely the outer membrane, periplasm, inner membrane and cytoplasm. Due to the exclusivity of peptidoglycan in the bacterial cell-wall, these players are the target of choice for many antibacterial agents. Our current understanding of cell-wall biochemistry and biogenesis in Gram-negative organisms stems mostly from studies of Escherichia coli. An incomplete knowledge on these processes exists for the opportunistic Gram-negative pathogen, Pseudomonas aeruginosa. In this review, cell-wall synthesis and recycling in the various cellular compartments are compared and contrasted between E. coli and P. aeruginosa. Despite the fact that there is a remarkable similarity of these processes between the two bacterial species, crucial differences alter their resistance to β-lactams, fluoroquinolones and aminoglycosides. One of the common mediators underlying resistance is the amp system whose mechanism of action is closely associated with the cell-wall recycling pathway. The activation of amp genes results in expression of AmpC β-lactamase through its cognate regulator AmpR which further regulates multi-drug resistance. In addition, other cell-wall recycling enzymes also contribute to antibiotic resistance. This comprehensive summary of the information should spawn new ideas on how to effectively target cell-wall processes to combat the growing resistance to existing antibiotics.

A finite element propagation model for extracting normal incidence impedance in nonprogressive acoustic wave fields

Science.gov (United States)

Watson, Willie R.; Jones, Michael G.; Tanner, Sharon E.; Parrott, Tony L.

1995-01-01

A propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented. The method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function. A finite element propagation model is combined with a coarse/fine grid impedance plane search technique to extract the impedance of the material. Results are presented for three different materials for which the impedance is known. For each material, the input data required for the prediction scheme was computed from modal theory and then contaminated by random error. The finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments. Thus, the method developed here provides a means for determining the impedance of materials in a nonprogressirve wave environment such as that usually encountered in a commercial aircraft engine and most laboratory settings.

Crack resistance of austenitic pipes with circumferential through-wall cracks

International Nuclear Information System (INIS)

Foerster, K.; Grueter, L.; Setz, W.; Bhandari, S.; Debaene, J.P.; Faidy, C.; Schwalbe, K.H.

1993-01-01

For monotonously increasing load the correct evaluation of the crack resistance properties of a structure is essential for safety analyses. Considerable attention has been given to the through-wall case, since this is generally believed to be the controlling case with regard to complete pipe failure. The maximum load conditions for circumferential crack growth in pipes under displacement-controlled loadings has been determined. The need for crack resistance curves, measured on circumferentially through-wall cracked straight pipes of austenitic stainless steel 316L under bending, is emphasized by the limitation in the data range on small specimens and by the differences in the procedures. To answer open questions and to improve calculational methods a joint fracture mechanics program is being performed by Electricite de France, Novatome and Siemens-Interatom. The working program contains experimental and theoretical investigations on the applicability of small-specimen data to real structures. 10 refs., 10 figs., 4 tabs

Measurement errors in multifrequency bioelectrical impedance analyzers with and without impedance electrode mismatch

International Nuclear Information System (INIS)

Bogónez-Franco, P; Nescolarde, L; Bragós, R; Rosell-Ferrer, J; Yandiola, I

2009-01-01

The purpose of this study is to compare measurement errors in two commercially available multi-frequency bioimpedance analyzers, a Xitron 4000B and an ImpediMed SFB7, including electrode impedance mismatch. The comparison was made using resistive electrical models and in ten human volunteers. We used three different electrical models simulating three different body segments: the right-side, leg and thorax. In the electrical models, we tested the effect of the capacitive coupling of the patient to ground and the skin–electrode impedance mismatch. Results showed that both sets of equipment are optimized for right-side measurements and for moderate skin–electrode impedance mismatch. In right-side measurements with mismatch electrode, 4000B is more accurate than SFB7. When an electrode impedance mismatch was simulated, errors increased in both bioimpedance analyzers and the effect of the mismatch in the voltage detection leads was greater than that in current injection leads. For segments with lower impedance as the leg and thorax, SFB7 is more accurate than 4000B and also shows less dependence on electrode mismatch. In both devices, impedance measurements were not significantly affected (p > 0.05) by the capacitive coupling to ground

Multi-Bunch effect of resistive wall in the beam delivery system of the Compact Linear Collider

CERN Document Server

Mutzner, Raphael; Pieloni, Tatiana; Rivkin, Leonid

2010-01-01

Wake fields in the CLIC Beam Delivery System (BDS) can cause severe single or multi-bunch effects leading to luminosity loss. The main contributors in the BDS are geometric and resistive wall wake fields of the collimators and resistive wall wakes of the beam pipe. The present master thesis focuses only on the multi-bunch effects from resistive wall. Using particle tracking with wake fields through the BDS, we have established the aperture radius, above which the effect of the wake fields becomes negligible. Simulations were later extended to include a realistic aperture model along the BDS as well as the collimators. We examine the two cases of 3 TeV and 500 GeV in this work, for stainless steel and copper pipes.

Analytic modeling of the feedback stabilization of resistive wall modes

International Nuclear Information System (INIS)

Pustovitov, Vladimir D.

2003-01-01

Feedback suppression of resistive wall modes (RWM) is studied analytically using a model based on a standard cylindrical approximation. Optimal choice of the input signal for the feedback, effects related to the geometry of the feedback active coils, RWM suppression in a configuration with ITER-like double wall, are considered here. The widespread opinion that the feedback with poloidal sensors is better than that with radial sensors is discussed. It is shown that for an ideal feedback system the best input signal would be a combination of radial and poloidal perturbations measured inside the vessel. (author)

Impairment of Cellulose Synthases Required for Arabidopsis Secondary Cell Wall Formation Enhances Disease Resistance[W

Science.gov (United States)

Hernández-Blanco, Camilo; Feng, Dong Xin; Hu, Jian; Sánchez-Vallet, Andrea; Deslandes, Laurent; Llorente, Francisco; Berrocal-Lobo, Marta; Keller, Harald; Barlet, Xavier; Sánchez-Rodríguez, Clara; Anderson, Lisa K.; Somerville, Shauna; Marco, Yves; Molina, Antonio

2007-01-01

Cellulose is synthesized by cellulose synthases (CESAs) contained in plasma membrane–localized complexes. In Arabidopsis thaliana, three types of CESA subunits (CESA4/IRREGULAR XYLEM5 [IRX5], CESA7/IRX3, and CESA8/IRX1) are required for secondary cell wall formation. We report that mutations in these proteins conferred enhanced resistance to the soil-borne bacterium Ralstonia solanacearum and the necrotrophic fungus Plectosphaerella cucumerina. By contrast, susceptibility to these pathogens was not altered in cell wall mutants of primary wall CESA subunits (CESA1, CESA3/ISOXABEN RESISTANT1 [IXR1], and CESA6/IXR2) or POWDERY MILDEW–RESISTANT5 (PMR5) and PMR6 genes. Double mutants indicated that irx-mediated resistance was independent of salicylic acid, ethylene, and jasmonate signaling. Comparative transcriptomic analyses identified a set of common irx upregulated genes, including a number of abscisic acid (ABA)–responsive, defense-related genes encoding antibiotic peptides and enzymes involved in the synthesis and activation of antimicrobial secondary metabolites. These data as well as the increased susceptibility of ABA mutants (abi1-1, abi2-1, and aba1-6) to R. solanacearum support a direct role of ABA in resistance to this pathogen. Our results also indicate that alteration of secondary cell wall integrity by inhibiting cellulose synthesis leads to specific activation of novel defense pathways that contribute to the generation of an antimicrobial-enriched environment hostile to pathogens. PMID:17351116

The inaccuracy of conventional one-dimensional parallel thermal resistance circuit model for two-dimensional composite walls

International Nuclear Information System (INIS)

Wong, K.-L.; Hsien, T.-L.; Hsiao, M.-C.; Chen, W.-L.; Lin, K.-C.

2008-01-01

This investigation is to show that two-dimensional steady state heat transfer problems of composite walls should not be solved by the conventionally one-dimensional parallel thermal resistance circuits (PTRC) model because the interface temperatures are not unique. Thus PTRC model cannot be used like its conventional recognized analogy, parallel electrical resistance circuits (PERC) model which has the unique node electric voltage. Two typical composite wall examples, solved by CFD software, are used to demonstrate the incorrectness. The numerical results are compared with those obtained by PTRC model, and very large differences are observed between their results. This proves that the application of conventional heat transfer PTRC model to two-dimensional composite walls, introduced in most heat transfer text book, is totally incorrect. An alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to the two-dimensional composite walls with isothermal boundaries. Results with acceptable accuracy can be obtained by the new model

Hardware Design of Tuber Electrical Resistance Tomography System Based on the Soil Impedance Test and Analysis

Directory of Open Access Journals (Sweden)

Liu Shuyi

2016-01-01

Full Text Available The hardware design of tuber electrical resistance tomography (TERT system is one of the key research problems of TERT data acquisition system. The TERT system can be applied to the tuber growth process monitoring in agriculture, i.e., the TERT data acquisition system can realize the real imaging of tuber plants in soil. In TERT system, the imaging tuber and soil multiphase medium is quite complexity. So, the impedance test and analysis of soil multiphase medium is very important to the design of sensitive array sensor subsystem and signals processing circuits. In the paper, the soil impedance test experimental is described and the results are analysed. The data acquisition hardware system is designed based on the result of soil medium impedance test and analysis. In the hardware design, the switch control chip ADG508, the instrumentation amplifier AD620 and programmable amplifier AD526 are employed. In the meantime, the phase locked loop technique for signal demodulation is introduced. The initial data collection is given and discussed under the conditions of existing plant tuber and no existing plant tuber. Conclusions of the hardware design of TERT system are presented.

Electrochemical impedance measurement of a carbon nanotube probe electrode

International Nuclear Information System (INIS)

Inaba, Akira; Takei, Yusuke; Kan, Tetsuo; Shimoyama, Isao; Matsumoto, Kiyoshi

2012-01-01

We measured and analyzed the electrochemical impedance of carbon nanotube (CNT) probe electrodes fabricated through the physical separation of insulated CNT bridges. The fabricated CNT electrodes were free-standing CNTs that were completely covered with an insulator, except for their tips. Typical dimensions of the nanoelectrodes were 1–10 nm in CNT diameter, 80–300 nm in insulator diameter, 0.5–4 μm in exposed CNT length and 1–10 μm in probe length. The electrochemical impedance at frequencies ranging from 40 Hz to 1 MHz was measured in physiological saline. The measured impedance of the CNT electrode was constant at 32 MΩ at frequencies below 1 kHz and was inversely proportional to frequency at frequencies above 10 kHz. By means of comparison with the parasitic capacitive impedance of the insulator membrane, we confirmed that the electrode was sufficiently insulated such that the measured constant impedance was given by the exposed CNT tip. Consequently, we can use the CNT electrode for highly localized electrochemical impedance measurements below 1 kHz. Considering an equivalent circuit and the nanoscopic dimensions of the CNT electrode, we demonstrated that the constant impedance was governed by diffusion impedance, whereas the solution resistance, charge-transfer resistance and double-layer capacitance were negligible. (paper)

The study of tribological and corrosion behavior of plasma nitrided 34CrNiMo6 steel under hot and cold wall conditions

International Nuclear Information System (INIS)

Maniee, A.; Mahboubi, F.; Soleimani, R.

2014-01-01

Highlights: • 34CrNiMo6 steel was plasma nitrided under hot and cold wall conditions. • The amount of ε phase in hot wall condition was more than that of cold wall condition. • Wear resistance of hot wall nitrided samples was more than cold wall treated ones. • Hot wall nitriding provides better corrosion behavior than cold wall nitriding. - Abstract: This paper reports on a comparative study of tribological and corrosion behavior of plasma nitrided 34CrNiMo6 low alloy steel under modern hot wall condition and conventional cold wall condition. Plasma nitriding was carried out at 500 °C and 550 °C with a 25% N 2 + 75% H 2 gas mixture for 8 h. The wall temperature of the chamber in hot wall condition was set to 400 °C. The treated specimens were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), microhardness and surface roughness techniques. The wear test was performed by pin-on-disc method. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were also used to evaluate the corrosion resistance of the samples. The results demonstrated that in both nitriding conditions, wear and corrosion resistance of the treated samples decrease with increasing temperature from 500 °C to 550 °C. Moreover, nitriding under hot wall condition at the same temperature provided slightly better tribological and corrosion behavior in comparison with cold wall condition. In consequence, the lowest friction coefficient, and highest wear and corrosion resistance were found on the sample treated under hot wall condition at 500 °C, which had the maximum surface hardness and ε-Fe 2–3 N phase

Feedback control of resistive wall modes in toroidal devices

International Nuclear Information System (INIS)

Liu, Y.Q.

2002-01-01

Active feedback of resistive wall modes is investigated using cylindrical theory and toroidal calculations. For tokamaks, good performance is obtained by using active coils with one set of coils in the poloidal direction and sensors detecting the poloidal field inside the first wall, located at the outboard mid-plane. With suitable width of the feedback coil such a system can give robust control with respect to variations in plasma current, pressure and rotation. Calculations are shown for ITER-like geometry with a double wall. The voltages and currents in the active coils are well within the design limits for ITER. Calculations for RFP's are presented for a finite number of coils both in the poloidal and toroidal directions. With 4 coils in the poloidal and 24 coils in the toroidal direction, all non-resonant modes can be stabilized both at high and low theta. Several types of sensors, including radial and internal poloidal or toroidal sensors, can stabilize the RWM, but poloidal sensors give the most robust performance. (author)

Line impedance estimation using model based identification technique

DEFF Research Database (Denmark)

Ciobotaru, Mihai; Agelidis, Vassilios; Teodorescu, Remus

2011-01-01

The estimation of the line impedance can be used by the control of numerous grid-connected systems, such as active filters, islanding detection techniques, non-linear current controllers, detection of the on/off grid operation mode. Therefore, estimating the line impedance can add extra functions...... into the operation of the grid-connected power converters. This paper describes a quasi passive method for estimating the line impedance of the distribution electricity network. The method uses the model based identification technique to obtain the resistive and inductive parts of the line impedance. The quasi...

Laboratory scale tests of electrical impedence tomography

International Nuclear Information System (INIS)

Binley, A; Daily, W; LaBredcque, D; Ramirez, A.

1998-01-01

Electrical impedance tomographs (magnitude and phase) of known, laboratory-scale targets are reported. Three methods are used to invert electrical impedance data and their tomographs compared. The first method uses an electrical resistance tomography (ERT) algonthm (designed for DC resistivity inversion) to perform impedance magnitude inversion and a linearized perturbation approach (PA) to invert the imaginary part. The second approximate method compares ERT magnitude inversions at two frequencies and uses the frequency effect (FE) to compute phase tomographs. The third approach, electrrcal impedance tomography (EIT), employs fully complex algebra to account for the real and imaginary components of electrical impedance data. The EIT approach provided useful magnitude and phase images for the frequency range of 0.0625 to 64 Hz; images for higher frequencies were not reliable. Comparisons of the ERT and EIT magnitude images show that both methods provided equivalent results for the water blank, copper rod and PVC rod targets. The EIT magnitude images showed better spatial resolutron for a sand-lead mixture target. Phase images located anomalies of both high and low contrast IP and provided better spatial resolution than the magnitude images. When IP was absent from the data, the EIT algorithm reconstructed phase values consistent with the data noise levels

Pulmonary vascular input impedance is a combined measure of pulmonary vascular resistance and stiffness and predicts clinical outcomes better than pulmonary vascular resistance alone in pediatric patients with pulmonary hypertension.

Science.gov (United States)

Hunter, Kendall S; Lee, Po-Feng; Lanning, Craig J; Ivy, D Dunbar; Kirby, K Scott; Claussen, Lori R; Chan, K Chen; Shandas, Robin

2008-01-01

Pulmonary vascular resistance (PVR) is the current standard for evaluating reactivity in children with pulmonary arterial hypertension (PAH). However, PVR measures only the mean component of right ventricular afterload and neglects pulsatile effects. We recently developed and validated a method to measure pulmonary vascular input impedance, which revealed excellent correlation between the zero harmonic impedance value and PVR and suggested a correlation between higher-harmonic impedance values and pulmonary vascular stiffness. Here we show that input impedance can be measured routinely and easily in the catheterization laboratory, that impedance provides PVR and pulmonary vascular stiffness from a single measurement, and that impedance is a better predictor of disease outcomes compared with PVR. Pressure and velocity waveforms within the main pulmonary artery were measured during right heart catheterization of patients with normal pulmonary artery hemodynamics (n = 14) and those with PAH undergoing reactivity evaluation (49 subjects, 95 conditions). A correction factor needed to transform velocity into flow was obtained by calibrating against cardiac output. Input impedance was obtained off-line by dividing Fourier-transformed pressure and flow waveforms. Exceptional correlation was found between the indexed zero harmonic of impedance and indexed PVR (y = 1.095x + 1.381, R2 = 0.9620). In addition, the modulus sum of the first 2 harmonics of impedance was found to best correlate with indexed pulse pressure over stroke volume (y = 13.39x - 0.8058, R2 = 0.7962). Among a subset of patients with PAH (n = 25), cumulative logistic regression between outcomes to total indexed impedance was better (R(L)2 = 0.4012) than between outcomes and indexed PVR (R(L)2 = 0.3131). Input impedance can be consistently and easily obtained from pulse-wave Doppler and a single catheter pressure measurement, provides comprehensive characterization of the main components of RV afterload, and

Laser and Pressure Resistance Weld of Thin-Wall Cladding for LWR Accident-Tolerant Fuels

Science.gov (United States)

Gan, J.; Jerred, N.; Perez, E.; Haggard, D. C.

2018-02-01

FeCrAl alloy with typical composition of approximately Fe-15Cr-5Al is considered a primary candidate cladding material for light water reactor accident-tolerant fuel because of its superior resistance to oxidation in high-temperature steam compared with Zircaloy cladding. Thin-walled FeCrAl cladding at 350 μm wall thickness is required, and techniques for joining endplug to cladding need to be developed. Fusion-based laser weld and solid-state joining with pressure resistance weld were investigated in this study. The results of microstructural characterization, mechanical property evaluation by tensile testing, and hydraulic pressure burst testing of the welds for the cladding-endplug specimen are discussed.

Transverse coupling impedance of the storage ring at the European Synchrotron Radiation Facility

Directory of Open Access Journals (Sweden)

T. F. Günzel

2006-11-01

Full Text Available The vertical and horizontal impedance budgets of the European Synchrotron Radiation Facility (ESRF storage ring are calculated by element-by-element wake potential calculation. Resistive wall wakes are calculated analytically; the short range geometrical wakes are calculated by a 3D electromagnetic field solver. The effect of the quadrupolar wakes due to the flatness of most ESRF vacuum chambers is included in the model. It can well explain the sensitivity of the horizontal single bunch threshold on vacuum chamber changes, in particular, in low-gap sections of the ESRF storage ring. The values of the current thresholds on the transverse planes could be predicted correctly by the model within a factor of 2.

Resistance to fire of walls constituted by hollow blocks: Experiments and thermal modeling

International Nuclear Information System (INIS)

Al Nahhas, F.; Ami Saada, R.; Bonnet, G.; Delmotte, P.

2007-01-01

The thermo-mechanical behavior of masonry walls is investigated from both experimental and theoretical points of view. Fire tests have been performed in order to evaluate the thermo-mechanical resistance of masonry wall submitted to a vertical load (13 ton/m) and exposed to temperatures ranging from 20 to 1200 o C. As a result we measure the temperature evolution inside the wall and evaluate the vertical and lateral displacements of this wall during heating for a period of 6 h. These results are affected significantly by phase-change phenomena which appeared as a plateau around o C in temperature-time curves. A theoretical model was then developed to describe the experimental results taking in to account convection, conduction and radiation phenomena inside the wall. In addition, liquid water migration using an enthalpic method is considered

Surface Resistance Measurements and Estimate of the Beam-Induced Resistive Wall Heating of the LHC Dipole Beam Screen

CERN Document Server

Caspers, Friedhelm; Ruggiero, F; Tan, J

1999-01-01

An estimate of the resistive losses in the LHC beam screen is given from cold surface resistance measurements using the shielded pair technique, with particular emphasis on the effect of a high magnetic field. Two different copper coating methods, namely electro-deposition and co-lamination, have been evaluated. Experimental data are compared with theories including the anomalous skin effect and the magneto-resistance effect. It is shown whether the theory underestimates or not the losses depends strongly on the RRR value, on the magnetic field and on the surface characteristics. In the pessimistic case and for nominal machine parameters, the estimated beam-induced resistive wall heating can be as large as 260 mW/m for two circulating beams.

Diversity of respiratory impedance based on quantitative computed tomography in patients with COPD.

Science.gov (United States)

Wada, Yosuke; Kitaguchi, Yoshiaki; Yasuo, Masanori; Ueno, Fumika; Kawakami, Satoshi; Fukushima, Kiyoyasu; Fujimoto, Keisaku; Hanaoka, Masayuki

2018-01-01

This study was conducted in order to investigate the diversity of respiratory physiology, including the respiratory impedance and reversibility of airway obstruction, based on quantitative computed tomography (CT) in patients with COPD. Medical records of 174 stable COPD patients were retrospectively reviewed to obtain the patients' clinical data, including the pulmonary function and imaging data. According to the software-based quantification of the degree of emphysema and airway wall thickness, the patients were classified into the "normal by CT" phenotype, the airway-dominant phenotype, the emphysema-dominant phenotype, and the mixed phenotype. The pulmonary function, including the respiratory impedance evaluated by using the forced oscillation technique (FOT) and the reversibility of airway obstruction in response to inhaled short-acting β 2 -agonists, was then compared among the four phenotypes. The respiratory system resistance at 5 and 20 Hz (R5 and R20) was significantly higher, and the respiratory system reactance at 5 Hz (X5) was significantly more negative in the airway-dominant and mixed phenotypes than in the other phenotypes. The within-breath changes of X5 (ΔX5) were significantly greater in the mixed phenotype than in the "normal by CT" and emphysema-dominant phenotypes. The FOT parameters (R5, R20, and X5) were significantly correlated with indices of the degree of airway wall thickness and significantly but weakly correlated with the reversibility of airway obstruction. There was no significant correlation between the FOT parameters (R5, R20, and X5) and the degree of emphysema. There is a diversity of respiratory physiology, including the respiratory impedance and reversibility of airway obstruction, based on quantitative CT in patients with COPD. The FOT measurements may reflect the degree of airway disease and aid in detecting airway remodeling in patients with COPD.

Hardware Design of Tuber Electrical Resistance Tomography System Based on the Soil Impedance Test and Analysis

OpenAIRE

Liu Shuyi; Deng Xiang; Jiang Zili; Tang Yu

2016-01-01

The hardware design of tuber electrical resistance tomography (TERT) system is one of the key research problems of TERT data acquisition system. The TERT system can be applied to the tuber growth process monitoring in agriculture, i.e., the TERT data acquisition system can realize the real imaging of tuber plants in soil. In TERT system, the imaging tuber and soil multiphase medium is quite complexity. So, the impedance test and analysis of soil multiphase medium is very important to the desi...

Cavity resonance absorption in ultra-high bandwidth CRT deflection structure by a resistive load

Science.gov (United States)

Dunham, M.E.; Hudson, C.L.

1993-05-11

An improved ultra-high bandwidth helical coil deflection structure for a cathode ray tube is described comprising a first metal member having a bore therein, the metal walls of which form a first ground plane; a second metal member coaxially mounted in the bore of the first metal member and forming a second ground plane; a helical deflection coil coaxially mounted within the bore between the two ground planes; and a resistive load disposed in one end of the bore and electrically connected to the first and second ground planes, the resistive load having an impedance substantially equal to the characteristic impedance of the coaxial line formed by the two coaxial ground planes to inhibit cavity resonance in the structure within the ultra-high bandwidth of operation. Preferably, the resistive load comprises a carbon film on a surface of an end plug in one end of the bore.

Dielectric and impedance spectroscopic studies of neodymium gallate

Energy Technology Data Exchange (ETDEWEB)

Sakhya, Anup Pradhan, E-mail: npshakya31@gmail.com [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Dutta, Alo [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India)

2016-05-01

The AC electrical properties of a polycrystalline neodymium gallate, NdGaO{sub 3} (NGO), synthesized by the sol–gel method have been investigated by employing impedance spectroscopy in the frequency range from 42 Hz to 5 MHz and in the temperature range from 323 K to 593 K. The X-ray diffraction analysis shows that the compound crystallizes in the orthorhombic phase with Pbnm space group at room temperature. Two relaxation processes with different relaxation times are observed from the impedance as well as modulus spectroscopic measurements, which have been attributed to the grain and the grain boundary effects at different temperatures in NGO. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element in parallel. It has been observed that the value of the capacitance and the resistance associated with the grain boundary is higher than those associated with the grain. The temperature dependent electrical conductivity shows the negative temperature coefficient of resistance. The frequency dependent conductivity spectra are found to follow the power law.

Evaluation of the corrosion resistance of anodized aluminum 6061 using electrochemical impedance spectroscopy (EIS)

International Nuclear Information System (INIS)

Huang Yuelong; Shih Hong; Huang, Huochuan; Daugherty, John; Wu Shun; Ramanathan, Sivakami; Chang, Chris; Mansfeld, Florian

2008-01-01

The corrosion resistance of anodized Al 6061 produced by two different anodizing and sealing processes was evaluated using electrochemical impedance spectroscopy (EIS). The scanning electron microscope (SEM) was employed to determine the surface structure and the thickness of the anodized layers. The EIS data revealed that there was very little change of the properties of the anodized layers for samples that were hard anodized in a mixed acid solution and sealed in hot water over a 365 day exposure period in a 3.5 wt% NaCl solution. The specific admittance A s and the breakpoint frequency f b remained constant with exposure time confirming that the hard anodizing process used in this study was very effective in providing excellent corrosion resistance of anodized Al 6061 over extended exposure periods. Some minor degradation of the protective properties of the anodized layers was observed for samples that were hard anodized in H 2 SO 4 and exposed to the NaCl solution for 14 days

Control of the Resistive Wall Mode with Internal Coils in the DIII-D Tokamak

International Nuclear Information System (INIS)

Okabayashi, M.; Bialek, J.; Bondeson, A.

2005-01-01

New coils were installed inside the vacuum vessel of the DIII-D device for producing nonaxisymmetric magnetic fields. These 'Internal-Coils' are predicted to stabilize the Resistive Wall Mode (RWM) branch of the long-wavelength external kink mode with plasma beta close to the ideal wall limit. Feedback using these new Internal-Coils was found to be more effective when compared with using the External-Coils located outside the vacuum vessel, because the location inside the vessel allows faster response and their geometry also couples better to the helical mode structure. A proper choice of feedback gain increased the plasma beta above the no-wall limit to C β ≥ 0.9, where C β is a measure of achievable beta above no-wall limit defined as (β-β no-wall.limit )/(β ideal.wall.limit )-)/(β no.wall.limit ). The feedback system with Internal-Coils can suppress the RWM up to the normalized growth rate γτ w > or ∼ 10 (τ w is the resistive flux penetration time of the wall). The feedback-driven dynamic error field correction helps to stabilize the RWM by reducing the rotational drag for Ω rot > Ω crit , where Ω rot is the angular rotation frequency of plasma and Ω crit is the critical value for the rotational stabilization. When Ω rot crit /2, the feedback system must stabilize the RWM mainly through direct magnetic control of the mode. The estimated Ω crit /Ω A is ∼ 2.5% by the MARS-F code analysis with experimentally observed profiles, where /Ω A is the Alfven angular rotational frequency at q 2 surface. The MARS-F code also predicts that for successful RWM magnetic feedback control the power supply characteristic time should be a fraction of the growth time of the targeted RWM. (author)

Electrical Impedance Measurements of PZT Nanofiber Sensors

Directory of Open Access Journals (Sweden)

Richard Galos

2017-01-01

Full Text Available Electrical impedance measurements of PZT nanofiber sensors were performed using a variety of methods over a frequency spectrum ranging from DC to 1.8 GHz. The nanofibers formed by electrospinning with diameters ranging from 10 to 150 nm were collected and integrated into sensors using microfabrication techniques. Special matching circuits with ultrahigh input impedance were fabricated to produce low noise, measurable sensor outputs. Material properties including resistivity and dielectric constant are derived from the impedance measurements. The resulting material properties are also compared with those of individual nanofibers being tested using conductive AFM and Scanning Conductive Microscopy.

Oxide impedance characteristics of the Zr-xNb alloys

International Nuclear Information System (INIS)

Park, S. Y.; Choi, B. K.; Jung, Y. H.; Jung, Y. H.

2002-01-01

To elucidate the correlation between the oxide impedance and corrosion characteristics of the Zr-xNb alloys, the long term corrosion test in high temperature / high pressure aqueous solution and the impedance test in the room temperature sulfate solution were performed. β-quenched plate specimens were heat-treated at 570 .deg. C for 500 hours to get the α+β Nb phase and the at 640 .deg. C for 10 hours to get the α+β Zr phase. The impedance test was conducted in sulfate solution for the initial corrosion test specimen (WG = 30 mg/dm 2 ). To evaluate the impedance date, 4 types of equivalent circuits were constructed by 5 parallel and serial RC elements. By using the equivalent circuits, the thickness of the inner and outer layers were calculated and the electric resistance of each layers were estimated. The corrosion behaviour of Zr-xNb alloys were quite different depending of the annealing condition and Nb-content. The corrosion resistance of the β Nb phase contained high Nb alloys were excellent rather than β Zr phase contained high Nb alloys. The electric resistance of the outer layer of β Zr phase contained high Nb alloy was twice larger than that of β Zr phase contained high Nb alloy, and in the case of outer layer 30% larger. So, the long term corrosion behaviors in high temperature could be estimated well by using the impedance test results

Nuclear radiation-warning detector that measures impedance

Science.gov (United States)

Savignac, Noel Felix; Gomez, Leo S; Yelton, William Graham; Robinson, Alex; Limmer, Steven

2013-06-04

This invention is a nuclear radiation-warning detector that measures impedance of silver-silver halide on an interdigitated electrode to detect light or radiation comprised of alpha particles, beta particles, gamma rays, X rays, and/or neutrons. The detector is comprised of an interdigitated electrode covered by a layer of silver halide. After exposure to alpha particles, beta particles, X rays, gamma rays, neutron radiation, or light, the silver halide is reduced to silver in the presence of a reducing solution. The change from the high electrical resistance (impedance) of silver halide to the low resistance of silver provides the radiation warning that detected radiation levels exceed a predetermined radiation dose threshold.

Creating low-impedance tetrodes by electroplating with additives

Science.gov (United States)

Ferguson, John E.; Boldt, Chris; Redish, A. David

2011-01-01

A tetrode is a bundle of four microwires that can record from multiple neurons simultaneously in the brain of a freely moving animal. Tetrodes are usually electroplated to reduce impedances from 2-3 MΩ to 200-500 kΩ (measured at 1 kHz), which increases the signal-to-noise ratio and allows for the recording of small amplitude signals. Tetrodes with even lower impedances could improve neural recordings but cannot be made using standard electroplating methods without shorting. We were able to electroplate tetrodes to 30-70 kΩ by adding polyethylene glycol (PEG) or multi-walled carbon nanotube (MWCNT) solutions to a commercial gold-plating solution. The MWCNTs and PEG acted as inhibitors in the electroplating process and created large-surface-area, low-impedance coatings on the tetrode tips. PMID:21379404

Control of the Resistive Wall Mode in Advanced Tokamak Plasmas on DIII-D

International Nuclear Information System (INIS)

Garofalo, A.M.; Strait, E.J.; Bialek, J.; Frederickson, E.; Gryaznevich, M.; Jensen, T.H.; Johnson, L.C.; La Haye, R.J.; Navratil, G.A.; Lazarus, E.A.; Luce, T.C.; Makowski, M.; Okabayashi, M.; Rice, B.W.; Scoville, J.T.; Turnbull, A.D.; Walker, M.L.

1999-01-01

Resistive wall mode (RWM) instabilities are found to be a limiting factor in advanced tokamak (AT) regimes with low internal inductance. Even small amplitude modes can affect the rotation profile and the performance of these ELMing H-mode discharges. Although complete stabilization of the RWM by plasma rotation has not yet been observed, several discharges with increased beam momentum and power injection sustained good steady-state performance for record time extents. The first investigation of active feedback control of the RWM has shown promising results: the leakage of the radial magnetic flux through the resistive wall can be successfully controlled, and the duration of the high beta phase can be prolonged. The results provide a comparative test of several approaches to active feedback control, and are being used to benchmark the analysis and computational models of active control

The effect of partial poloidal wall sections on the wall stabilization of external kink modes

International Nuclear Information System (INIS)

Ward, D.J.

1996-02-01

An analysis of the effect on the wall stabilization of external kink modes due to toroidally continuous gaps in the resistive wall is performed. The effects with and without toroidal rotation are studied. For a high-β equilibrium, the mode structure is localized on the outboard side. Therefore, outboard gaps greatly increase the growth rate when there is no rotation. For resistive wall stabilization by toroidal rotation, the presence of gaps has the same effect as moving the wall farther away, i.e. destabilizing for the ideal plasma mode, and stabilizing for the resistive wall mode. The region of stability, in terms of wall position, is reduced in size and moved closer to the plasma. However, complete stabilization becomes possible at considerably reduced rotation frequencies. For a high-β, reverse-shear equilibrium both the resistive wall mode and the ideal plasma mode can be stabilized by close fitting discrete passive plates on the outboard side. The necessary toroidal rotation frequency to stabilize the resistive wall mode using these plates is reduced by a factor of three compared to that for a poloidally continuous and complete wall at the same plasma-wall separation. (author) 15 figs., 24 refs

Design of optimized impedance transformer for ICRF antenna in LHD

Energy Technology Data Exchange (ETDEWEB)

Saito, K., E-mail: saito@nifs.ac.jp [National Institute for Fusion Science, Toki, Gifu, 509-5292 (Japan); Seki, T.; Kasahara, H.; Seki, R.; Kumazawa, R.; Nomura, G.; Shimpo, F.; Mutoh, T. [National Institute for Fusion Science, Toki, Gifu, 509-5292 (Japan)

2013-10-15

Highlights: ► We developed optimization method of impedance transformer for ICRF antenna. ► Power loss will be one-third with the optimized impedance transformer. ► Possibility of damage on the transmission line will be drastically reduced. ► High performance will be kept in the wide antenna impedance region. -- Abstract: A pair of ion cyclotron range of frequencies (ICRF) antennas in the large helical device (LHD), HAS antennas showed high efficiency in minority ion heating. However the low loading resistance must be increased to prevent breakdown in transmission line. Moreover, the voltage and the current around the feed-through must be reduced to protect it. For these purpose, we developed a design procedure of the impedance transformer for HAS antennas. To optimize the transformer, the inner conductors were divided into several segments and the radii of them were given discretely and independently. The maximum effective loading resistance was obtained by using all combinations of radii within the limitations of the voltage and current at the feed-through and the electric field on the transformer. To get a precise solution, this procedure was repeated several times by narrowing the range of radii of inner conductors. Then the optimized impedance transformer was designed by smoothing the radii of inner conductors. For the typical discharge, the voltage and current at the feed-through were reduced to the half of the original values with the same power. The effective loading resistance was increased to more than four times. High performance is expected in wide impedance region.

Resistive wall mode active control physics design for KSTAR

International Nuclear Information System (INIS)

Park, Y. S.; Sabbagh, S. A.; Bialek, J. M.; Berkery, J. W.; Bak, J. G.; Lee, S. G.; Oh, Y. K.

2014-01-01

As KSTAR H-mode operation approaches the region where the resistive wall mode (RWM) can be unstable, an important issue for future long pulse, high beta plasma operation is to evaluate RWM active feedback control performance using a planned active/passive RWM stabilization system on the device. In particular, an optimal design of feedback sensors allows mode stabilization up to the highest achievable β N close to the ideal with-wall limit, β N wall , with reduced control power requirements. The computed ideal n = 1 mode structure from the DCON code has been input to the VALEN-3D code to calculate the projected performance of an active RWM control system in the KSTAR three-dimensional conducting structure device geometry. Control performance with the midplane locked mode detection sensors, off-midplane saddle loops, and magnetic pickup coils is examined. The midplane sensors measuring the radial component of the mode perturbation is found to be strongly affected by the wall eddy current. The off-axis saddle loops with proper compensation of the prompt applied field are computed to provide stabilization at β N up to 86% of β N wall but the low RWM amplitude computed in the off-axis regions near the sensors can produce a low signal-to-noise ratio. The required control power and bandwidth are also estimated with varied noise levels in the feedback sensors. Further improvements have been explored by examining a new RWM sensor design motivated by the off-midplane poloidal magnetic field sensors in NSTX. The new sensors mounted off of the copper passive stabilizer plates near the device midplane show a clear advantage in control performance corresponding to achieving 99% of β N wall without the need of compensation of the prompt field. The result shows a significant improvement of RWM feedback stabilization using the new sensor set which motivates a future feedback sensor upgrade

Soft x-ray measurements of resistive wall mode behavior in NSTX

Energy Technology Data Exchange (ETDEWEB)

Delgado-Aparicio, L; Bell, R E; Gerhardt, S P; LeBlanc, B; Menard, J; Paul, S; Roquemore, L [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Stutman, D; Tritz, K; Finkenthal, M [Johns Hopkins University, Baltimore, MD 21218 (United States); Sabbagh, S A; Berkery, J W; Levesque, J P [Columbia University, New York, NY 10027 (United States); Lee, K C, E-mail: ldelgado@pppl.gov [University of California at Davis, Davis, CA 95616 (United States)

2011-03-15

A multi-energy soft x-ray (ME-SXR) array is used for the characterization of resistive wall modes (RWMs) in the National Spherical Torus Experiment (NSTX). Modulations in the time history of the ME-SXR emissivity profiles indicate the existence of edge density and core temperature fluctuations in good agreement with the slow evolution of the n = 1 magnetic perturbation measured by the poloidal and radial RWM coils. The characteristic 20-25 Hz frequency in the SXR diagnostics is approximately that of the n = 1 stable RWM, which is also near the measured peak of the resonant field amplification (RFA) and inversely proportional to the wall time. Together with the magnetics, the ME-SXR measurements suggest that in NSTX the RWM is not restricted exclusively to the reactor wall and edge, and that acting with the stabilizing coils on its global structure may result in density and temperature fluctuations that can be taken into account when designing the feedback process.

Impedance of thin film cathodes: thickness and current collector dependence

NARCIS (Netherlands)

Boukamp, Bernard A.; Hildenbrand, N.; Bouwmeester, Henricus J.M.; Blank, David H.A.

2015-01-01

The influence of the layer thickness of mixed ionic–electronic conducting (MIEC) cathodes and the type of noble metal current collector on the apparent surface exchange resistance is studied with impedance spectroscopy. The impedance data is analyzed with the ‘General Finite Length Diffusion’

Forced convection heat transfer in rectangular ducts: general case of wall resistances and peripheral conduction

Energy Technology Data Exchange (ETDEWEB)

Lyczkowski, R. W. [Institute of Gas Technology, Chicago, IL (United States); Solbrig, C. W. [Commonwealth Edison Co., Chicago, IL (United States); Gidaspow, D. [Illinois Inst. of Technology, Chicago, IL (United States)

1980-01-01

A numerical solution for laminar flow heat transfer between a flowing gas and its containing rectangular duct has been obtained for many different boundary conditions. The problem has been solved for the cases of insulation on no walls, one wall, two walls, and three walls with various finite resistances on the remaining walls. Results have been obtained for several duct aspect ratios in the thermal entrance and in the fully developed regions, including the constant temperature cases. When one wall is insulated and the other three are at constant temperature, the maximum temperature occurs in the fluid rather than on the insulated wall. This maximum moves toward the insulated wall with increasing axial distance. Nusselt numbers for the same constant flux on all four walls with peripheral conduction lie in a narrow band bounded by zero and infinite peripheral conduction cases. A dimensionless wall conduction group of four can be considered infinite for the purpose of estimating fully developed Nusselt numbers to within an accuracy of 3%. A decrease in wall and bulk temperatures by finite wall conduction has been demonstrated for the case of a black body radiation boundary condition.

Determination of SoH of Lead-Acid Batteries by Electrochemical Impedance Spectroscopy

Directory of Open Access Journals (Sweden)

Monika Kwiecien

2018-05-01

Full Text Available The aging mechanisms of lead-acid batteries change the electrochemical characteristics. For example, sulfation influences the active surface area, and corrosion increases the resistance. Therefore, it is expected that the state of health (SoH can be reflected through differentiable changes in the impedance of a lead-acid battery. However, for lead-acid batteries, no reliable SoH algorithm is available based on single impedance values or the spectrum. Additionally, the characteristic changes of the spectrum during aging are unknown. In this work, lead-acid test cells were aged under specific cycle regimes known as AK3.4, and periodic electrochemical impedance spectroscopy (EIS measurements and capacity tests were conducted. It was examined that single impedance values increased linearly with capacity decay, but with varying slopes depending on the pre-history of the cell and measurement frequency of impedance. Thereby, possible reasons for ineffective SoH estimation were found. The spectra were fitted to an equivalent electrical circuit containing, besides other elements, an ohmic and a charge-transfer resistance of the negative electrode. The linear increase of the ohmic resistance and the charge-transfer resistance were characterized for the performed cyclic aging test. Results from chemical analysis confirmed the expected aging process and the correlation between capacity decay and impedance change. Furthermore, the positive influence of charging on the SoH could be detected via EIS. The results presented here show that SoH estimation using EIS can be a viable technique for lead-acid batteries.

Wall current monitor for SPring-8 linac

International Nuclear Information System (INIS)

Yanagida, Kenichi; Yamada, Kouji; Yokoyama, Minoru

1994-06-01

A fast rise time, broad band width and wide dynamic range wall current monitor was developed for SPring-8 linac. The performances are a rise time of ∼250ps, an effective impedance of 1.4Ω (output of ∼1.4V/A) and a bandwidth of 18kHz-2GHz. From a result of examination using 40ns electron beam, a significant change of effective impedance was not observed when a peak current was changed up to 12A or when a beam was moved by 8mm in a vacuum pipe. A circuit model that includes a core inductor loop was constructed. Using this model effective impedance and band width were calculated and compared to measured ones. They agreed very well except one part. In consequence the mechanism of wall current monitor can be explained by means of this model. (author)

Organic electrochemical transistors for cell-based impedance sensing

International Nuclear Information System (INIS)

Rivnay, Jonathan; Ramuz, Marc; Hama, Adel; Huerta, Miriam; Owens, Roisin M.; Leleux, Pierre

2015-01-01

Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal

THIN-WALLED CROSS SECTION SHAPE INFLUENCE ON STEEL MEMBER RESISTANCE

Directory of Open Access Journals (Sweden)

Elżbieta Urbańska-Galewska

2016-03-01

Full Text Available This work describes why trending thin-walled technology is achieving popularity in steel construction sector. A purpose of this article is to present the influence of the cold-formed element cross-section shape on an axial compression and a bending moment resistance. The authors have considered four different shapes assuming constant section area and thickness. Calculations were based on three different steel grades taking into account local, distortional and overall buckling. The results are presented in a tabular and a graphical way and clearly confirm that cross-section forming distinctly impact the cold-formed member resistance. The authors choose these cross-sections that work better in compression state and the other (those slender and high that function more efficiently are subjected to bending.

Strain-dependent electrical resistance of multi-walled carbon nanotube/polymer composite films

International Nuclear Information System (INIS)

Park, Myounggu; Kim, Hyonny; Youngblood, Jeffrey P

2008-01-01

The strain-dependent electrical resistance characteristics of multi-walled carbon nanotube (MWCNT)/polymer composite films were investigated. In this research, polyethylene oxide (PEO) is used as the polymer matrix. Two representative volume fractions of MWCNT/PEO composite films were selected: 0.56 vol% (near the percolation threshold) and 1.44 vol% (away from the percolation threshold) of MWCNT. An experimental setup which can measure electrical resistance and strain simultaneously and continuously has been developed. Unique and repeatable relationships in resistance versus strain were obtained for multiple specimens with different volume fractions of MWCNT. The overall pattern of electrical resistance change versus strain for the specimens tested consists of linear and nonlinear regions. A resistance change model to describe the combination of linear and nonlinear modes of electrical resistance change as a function of strain is suggested. The unique characteristics in electrical resistance change for different volume fractions imply that MWCNT/PEO composite films can be used as tunable strain sensors and for application into embedded sensor systems in structures

Design of squat shear walls using continuous strut-and-tie resistant models

International Nuclear Information System (INIS)

Santos, S.H. de C; Silva, R.E. da

1993-01-01

A new approach is presented for designing squat shear walls, subjected to seismic loading. In this approach, the strut-and-tie resistant models, proposed by Schlaich et al., are generalized in order to analyze continuous fields of compression and tension stresses. The application of the presented methodology is illustrated through numerical examples. (author)

Evaluation of the corrosion resistance of anodized aluminum 6061 using electrochemical impedance spectroscopy (EIS)

Energy Technology Data Exchange (ETDEWEB)

Huang Yuelong [Corrosion and Environmental Effects Laboratory (CEEL), Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-0241 (United States); Shih Hong [Lam Research Corporation, 4400 Cushing Parkway, Fremont, CA 94538 (United States)], E-mail: hong.shih@lamrc.com; Huang, Huochuan; Daugherty, John; Wu Shun; Ramanathan, Sivakami; Chang, Chris [Lam Research Corporation, 4400 Cushing Parkway, Fremont, CA 94538 (United States); Mansfeld, Florian [Corrosion and Environmental Effects Laboratory (CEEL), Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-0241 (United States)], E-mail: mansfeld@usc.edu

2008-12-15

The corrosion resistance of anodized Al 6061 produced by two different anodizing and sealing processes was evaluated using electrochemical impedance spectroscopy (EIS). The scanning electron microscope (SEM) was employed to determine the surface structure and the thickness of the anodized layers. The EIS data revealed that there was very little change of the properties of the anodized layers for samples that were hard anodized in a mixed acid solution and sealed in hot water over a 365 day exposure period in a 3.5 wt% NaCl solution. The specific admittance A{sub s} and the breakpoint frequency f{sub b} remained constant with exposure time confirming that the hard anodizing process used in this study was very effective in providing excellent corrosion resistance of anodized Al 6061 over extended exposure periods. Some minor degradation of the protective properties of the anodized layers was observed for samples that were hard anodized in H{sub 2}SO{sub 4} and exposed to the NaCl solution for 14 days.

Static resistivity image of a cubic saline phantom in magnetic resonance electrical impedance tomography (MREIT).

Science.gov (United States)

Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyeong; Kwon, Ohin; Seo, Jin Keun; Baek, Woon Sik

2003-05-01

In magnetic resonance electrical impedance tomography (MREIT) we inject currents through electrodes placed on the surface of a subject and try to reconstruct cross-sectional resistivity (or conductivity) images using internal magnetic flux density as well as boundary voltage measurements. In this paper we present a static resistivity image of a cubic saline phantom (50 x 50 x 50 mm3) containing a cylindrical sausage object with an average resistivity value of 123.7 ohms cm. Our current MREIT system is based on an experimental 0.3 T MRI scanner and a current injection apparatus. We captured MR phase images of the phantom while injecting currents of 28 mA through two pairs of surface electrodes. We computed current density images from magnetic flux density images that are proportional to the MR phase images. From the current density images and boundary voltage data we reconstructed a cross-sectional resistivity image within a central region of 38.5 x 38.5 mm2 at the middle of the phantom using the J-substitution algorithm. The spatial resolution of the reconstructed image was 64 x 64 and the reconstructed average resistivity of the sausage was 117.7 ohms cm. Even though the error in the reconstructed average resistivity value was small, the relative L2-error of the reconstructed image was 25.5% due to the noise in measured MR phase images. We expect improvements in the accuracy by utilizing an MRI scanner with higher SNR and increasing the size of voxels scarifying the spatial resolution.

Control of the resistive wall mode with internal coils in the DIII-D tokamak

International Nuclear Information System (INIS)

Okabayashi, M.; Bialek, J.; Bondeson, A.; Chance, M.S.; Chu, M.S.; Garofalo, A.M.; Hatcher, R.; In, Y.; Jackson, G.L.; Jayakumar, R.J.; Jensen, T.H.; Katsuro-Hopkins, O.; Haye, R.J. La; Liu, Y.Q.; Navratil, G.A.; Reimerdes, H.; Scoville, J.T.; Strait, E.J.; Takechi, M.; Turnbull, A.D.; Gohil, P.; Kim, J.S.; Makowski, M.A.; Manickam, J.; Menard, J.

2005-01-01

Internal coils, 'I-Coils', were installed inside the vacuum vessel of the DIII-D device to generate non-axisymmetric magnetic fields to act directly on the plasma. These fields are predicted to stabilize the resistive wall mode (RWM) branch of the long-wavelength external kink mode with plasma beta close to the ideal wall limit. Feedback using these I-Coils was found to be more effective as compared to using external coils located outside the vacuum vessel. Locating the coils inside the vessel allows for a faster response and the coil geometry also allows for better coupling to the helical mode structure. Initial results were reported previously (Strait E.J. et al 2004 Phys. Plasmas 11 2505). This paper reports on results from extended feedback stabilization operations, achieving plasma parameters up to the regime of C β ∼ 1.0 and open loop growth rates of γ open τ w ∼ 25 where the RWM was predicted to be unstable with only the 'rotational viscous stabilization mechanism'. Here C β ∼ (β - β no-wall.limit )/(β ideal.wall.limit - β no-wall.limit ) is a measure of the beta relative to the stability limits without a wall and with a perfectly conducting wall, and τ w is the resistive flux penetration time of the wall. These feedback experimental results clarified the processes of dynamic error field correction and direct RWM stabilization, both of which took place simultaneously during RWM feedback stabilization operation. MARS-F modelling provides a critical rotation velocity in reasonable agreement with the experiment and predicts that the growth rate increases rapidly as rotation decreases below the critical. The MARS-F code also predicted that for successful RWM magnetic feedback, the characteristic time of the power supply should be limited to a fraction of the growth time of the targeted RWM. The possibility of further improvements in the presently achievable range of operation of feedback gain values is also discussed

Impedance study of membrane dehydration and compression in proton exchange membrane fuel cells

Energy Technology Data Exchange (ETDEWEB)

Le Canut, Jean-Marc; Latham, Ruth; Merida, Walter; Harrington, David A. [Institute for Integrated Energy Systems, University of Victoria, Victoria, British Columbia (Canada)

2009-07-15

Electrochemical impedance spectroscopy (EIS) is used to measure drying and rehydration in proton exchange membrane fuel cells running under load. The hysteresis between forward and backward acquisition of polarization curves is shown to be largely due to changes in the membrane resistance. Drying tests are carried out with hydrogen and simulated reformate (hydrogen and carbon dioxide), and quasi-periodic drying and rehydration conditions are studied. The membrane hydration state is clearly linked to the high-frequency arc in the impedance spectrum, which increases in size for dry conditions indicating an increase in membrane resistance. Changes in impedance spectra as external compression is applied to the cell assembly show that EIS can separate membrane and interfacial effects, and that changes in membrane resistance dominate. Reasons for the presence of a capacitance in parallel with the membrane resistance are discussed. (author)

A Retrofit Technique for Kicker Beam-Coupling Impedance Reduction

CERN Document Server

Caspers, Friedhelm; Kroyer, T; Timmins, M; Uythoven, J; Kurennoy, S

2004-01-01

The reduction of the impedance of operational ferrite kicker structures may be desirable in order to avoid rebuilding such a device. Often resistively coated ceramic plates or tubes are installed for this purpose but at the expense of available aperture. Ceramic U-shaped profiles with a resistive coating fitting between the ellipse of the beam and the rectangular kicker aperture have been used to significantly reduce the impedance of the magnet, while having a limited effect on the available physical aperture. Details of this method, constraints, measurements and simulation results as well as practical aspects are presented and discussed.

Resistive wall modes and error field amplification

International Nuclear Information System (INIS)

Boozer, Allen H.

2003-01-01

Resistive wall modes and the rapid damping of plasma rotation by the amplification of magnetic field errors are related physical phenomena that affect the performance of the advanced tokamak and spherical torus plasma confinement devices. Elements of our understanding of these phenomena and the code that is used to design the major experimental facilities are based on the electrical circuit representation of the response of the plasma to perturbations. Although the circuit representation of the plasma may seem heuristic, this representation can be rigorously obtained using Maxwell's equations and linearity for plasmas that evolve on a disparate time scale from that of external currents. These and related results are derived. In addition methods are given for finding the plasma information that the circuit representation requires using post-processors for codes that calculate perturbed plasma equilibria

Stability and Control of Burning Tokamak Plasmas with Resistive Walls: Final Technical Report

Energy Technology Data Exchange (ETDEWEB)

Miller, George [Univ. of Tulsa, OK (United States); Brennan, Dylan [Princeton Univ., NJ (United States); Cole, Andrew [Columbia Univ., New York, NY (United States); Finn, John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-10-02

This project is focused on theoretical and computational development for quantitative prediction of the stability and control of the equilibrium state evolution in toroidal burning plasmas, including its interaction with the surrounding resistive wall. The stability of long pulse burning plasmas is highly sensitive to the physics of resonant layers in the plasma, sources of momentum and flow, kinetic effects of energetic particles, and boundary conditions at the wall, including feedback control and error fields. In ITER in particular, the low toroidal flow equilibrium state, sustained primarily by energetic alpha particles from fusion reactions, will require the consideration of all of these key elements to predict quantitatively the stability and evolution. The principal investigators on this project have performed theoretical and computational analyses, guided by analytic modeling, to address this physics in realistic configurations. The overall goal has been to understand the key physics mechanisms that describe stable toroidal burning plasmas under active feedback control. Several relevant achievements have occurred during this project, leading to publications and invited conference presentations. In theoretical efforts, with the physics of the resonant layers, resistive wall, and toroidal momentum transport included, this study has extended from cylindrical resistive plasma - resistive wall models with feedback control to toroidal geometry with strong shaping to study mode coupling effects on the stability. These results have given insight into combined tearing and resistive wall mode behavior in simulations and experiment, while enabling a rapid exploration of plasma parameter space, to identify possible domains of interest for large plasma codes to investigate in more detail. Resonant field amplification and quasilinear torques in the presence of error fields and velocity shear have also been investigated. Here it was found, surprisingly, that the Maxwell

Impedance Characterisation of the SPS Wire Scanner

CERN Document Server

AUTHOR|(CDS)2091911; Prof. Sillanpää, Mika

As a beam diagnostic tool, the SPS wire scanner interacts with the proton bunches traversing the vacuum pipes of the Super Proton Synchrotron particle accelerator. Following the interaction, the bunches decelerate or experience momentum kicks off-axis and couple energy to the cavity walls, resonances and to the diagnostic tool, the scanning wire. The beam coupling impedance and, in particular, the beam induced heating of the wire motivate the characterisation and redesign of the SPS wire scanner. In this thesis, we characterise RF-wise the low frequency modes of the SPS wire scanner. These have the highest contribution to the impedance. We measure the cavity modes in terms of resonance frequency and quality factor by traditional measurement techniques and data analysis. We carry out a 4-port measurement to evaluate the beam coupling to the scanning wire, that yields the spectral heating power. If combined with the simulations, one is able to extract the beam coupling impedance and deduce the spectral dissipa...

Surface impedance and optimum surface resistance of a superconductor with an imperfect surface

Science.gov (United States)

Gurevich, Alex; Kubo, Takayuki

2017-11-01

We calculate a low-frequency surface impedance of a dirty, s -wave superconductor with an imperfect surface incorporating either a thin layer with a reduced pairing constant or a thin, proximity-coupled normal layer. Such structures model realistic surfaces of superconducting materials which can contain oxide layers, absorbed impurities, or nonstoichiometric composition. We solved the Usadel equations self-consistently and obtained spatial distributions of the order parameter and the quasiparticle density of states which then were used to calculate a low-frequency surface resistance Rs(T ) and the magnetic penetration depth λ (T ) as functions of temperature in the limit of local London electrodynamics. It is shown that the imperfect surface in a single-band s -wave superconductor results in a nonexponential temperature dependence of Z (T ) at T ≪Tc which can mimic the behavior of multiband or d -wave superconductors. The imperfect surface and the broadening of the gap peaks in the quasiparticle density of states N (ɛ ) in the bulk give rise to a weakly temperature-dependent residual surface resistance. We show that the surface resistance can be optimized and even reduced below its value for an ideal surface by engineering N (ɛ ) at the surface using pair-breaking mechanisms, particularly by incorporating a small density of magnetic impurities or by tuning the thickness and conductivity of the normal layer and its contact resistance. The results of this work address the limit of Rs in superconductors at T ≪Tc , and the ways of engineering the optimal density of states by surface nanostructuring and impurities to reduce losses in superconducting microresonators, thin-film strip lines, and radio-frequency cavities for particle accelerators.

Effects of centrifugal modification of magnetohydrodynamic equilibrium on resistive wall mode stability

International Nuclear Information System (INIS)

Shiraishi, J.; Aiba, N.; Miyato, N.; Yagi, M.

2014-01-01

Toroidal rotation effects are self-consistently taken into account not only in the linear magnetohydrodynamic (MHD) stability analysis but also in the equilibrium calculation. The MHD equilibrium computation is affected by centrifugal force due to the toroidal rotation. To study the toroidal rotation effects on resistive wall modes (RWMs), a new code has been developed. The RWMaC modules, which solve the electromagnetic dynamics in vacuum and the resistive wall, have been implemented in the MINERVA code, which solves the Frieman–Rotenberg equation that describes the linear ideal MHD dynamics in a rotating plasma. It is shown that modification of MHD equilibrium by the centrifugal force significantly reduces growth rates of RWMs with fast rotation in the order of M 2  = 0.1 where M is the Mach number. Moreover, it can open a stable window which does not exist under the assumption that the rotation affects only the linear dynamics. The rotation modifies the equilibrium pressure gradient and current density profiles, which results in the change of potential energy including rotational effects. (paper)

Mediated Electron Transfer at Vertically Aligned Single-Walled Carbon Nanotube Electrodes During Detection of DNA Hybridization

Science.gov (United States)

Wallen, Rachel; Gokarn, Nirmal; Bercea, Priscila; Grzincic, Elissa; Bandyopadhyay, Krisanu

2015-06-01

Vertically aligned single-walled carbon nanotube (VASWCNT) assemblies are generated on cysteamine and 2-mercaptoethanol (2-ME)-functionalized gold surfaces through amide bond formation between carboxylic groups generated at the end of acid-shortened single-walled carbon nanotubes (SWCNTs) and amine groups present on the gold surfaces. Atomic force microscopy (AFM) imaging confirms the vertical alignment mode of SWCNT attachment through significant changes in surface roughness compared to bare gold surfaces and the lack of any horizontally aligned SWCNTs present. These SWCNT assemblies are further modified with an amine-terminated single-stranded probe-DNA. Subsequent hybridization of the surface-bound probe-DNA in the presence of complementary strands in solution is followed using impedance measurements in the presence of Fe(CN)6 3-/4- as the redox probe in solution, which show changes in the interfacial electrochemical properties, specifically the charge-transfer resistance, due to hybridization. In addition, hybridization of the probe-DNA is also compared when it is attached directly to the gold surfaces without any intermediary SWCNTs. Contrary to our expectations, impedance measurements show a decrease in charge-transfer resistance with time due to hybridization with 300 nM complementary DNA in solution with the probe-DNA attached to SWCNTs. In contrast, an increase in charge-transfer resistance is observed with time during hybridization when the probe-DNA is attached directly to the gold surfaces. The decrease in charge-transfer resistance during hybridization in the presence of VASWCNTs indicates an enhancement in the electron transfer process of the redox probe at the VASWCNT-modified electrode. The results suggest that VASWCNTs are acting as mediators of electron transfer, which facilitate the charge transfer of the redox probe at the electrode-solution interface.

RHIC ABORT KICKER WITH REDUCED COUPLING IMPEDANCE

International Nuclear Information System (INIS)

HAHN, H.; DAVINO, D.

2002-01-01

Kicker magnets typically represent the most important contributors to the transverse impedance budget of accelerators and storage rings. Methods of reducing the impedance value of the SNS extraction kicker presently under construction and, in view of a future performance upgrade, that of the RHIC abort kicker have been thoroughly studied at this laboratory. In this paper, the investigation of a potential improvement from using ferrite different from the BNL standard CMD5005 is reported. Permeability measurements of several ferrite types have been performed. Measurements on two kicker magnets using CMD5005 and C2050 suggest that the impedance of a magnet without external resistive damping, such as the RHIC abort kicker, would benefit

Feedback control of resistive wall modes in toroidal devices

International Nuclear Information System (INIS)

Liu Yueqiang; Bondeson, A.; Gregoratto, D.; Fransson, C.M.; Gribov, Y.; Paccagnella, R.

2003-01-01

Feedback of nonaxisymmetric resistive wall modes (RWM) is studied analytically for cylindrical plasmas and computationally for high beta tokamaks. Internal poloidal sensors give superior performance to radial sensors, and this is explained by the distribution of poles and residues for the transfer functions. A single poloidal array of feedback coils allows robust control with respect to variations in plasma pressure, current and rotation velocity. The control analysis is applied to advanced scenarios for ITER. Studies are also shown of configurations with multiple poloidal coils and of feedback systems for nonresonant MHD instabilities in reversed field pinches. (author)

Impedance Scaling and Impedance Control

International Nuclear Information System (INIS)

Chou, W.; Griffin, J.

1997-06-01

When a machine becomes really large, such as the Very Large Hadron Collider (VLHC), of which the circumference could reach the order of megameters, beam instability could be an essential bottleneck. This paper studies the scaling of the instability threshold vs. machine size when the coupling impedance scales in a ''normal'' way. It is shown that the beam would be intrinsically unstable for the VLHC. As a possible solution to this problem, it is proposed to introduce local impedance inserts for controlling the machine impedance. In the longitudinal plane, this could be done by using a heavily detuned rf cavity (e.g., a biconical structure), which could provide large imaginary impedance with the right sign (i.e., inductive or capacitive) while keeping the real part small. In the transverse direction, a carefully designed variation of the cross section of a beam pipe could generate negative impedance that would partially compensate the transverse impedance in one plane

Resistive wall heating due to image current on the beam chamber for a superconducting undulator.

Energy Technology Data Exchange (ETDEWEB)

Kim, S. H. (Accelerator Systems Division (APS))

2012-03-27

The image-current heating on the resistive beam chamber of a superconducting undulator (SCU) was calculated based on the normal and anomalous skin effects. Using the bulk resistivity of copper for the beam chamber, the heat loads were calculated for the residual resistivity ratios (RRRs) of unity at room temperature to 100 K at a cryogenic temperature as the reference. Then, using the resistivity of the specific aluminum alloy 6053-T5, which will be used for the SCU beam chamber, the heat loads were calculated. An electron beam stored in a storage ring induces an image current on the inner conducting wall, mainly within a skin depth, of the beam chamber. The image current, with opposite charge to the electron beam, travels along the chamber wall in the same direction as the electron beam. The average current in the storage ring consists of a number of bunches. When the pattern of the bunched beam is repeated according to the rf frequency, the beam current may be expressed in terms of a Fourier series. The time structure of the image current is assumed to be the same as that of the beam current. For a given resistivity of the chamber inner wall, the application ofthe normal or anomalous skin effect will depend on the harmonic numbers of the Fourier series of the beam current and the temperature of the chamber. For a round beam chamber with a ratius r, much larger than the beam size, one can assume that the image current density as well as the density square, may be uniform around the perimeter 2{pi}r. For the SCU beam chamber, which has a relatively narrow vertical gap compared to the width, the effective perimeter was estimated since the heat load should be proportional to the inverse of the perimeter.

Estimate of the longitudinal and transverse impedances for the superconducting super collider

International Nuclear Information System (INIS)

Ng, K.Y.

1984-01-01

We try to estimate the longitudinal impedance per harmonic Z/sub L//n as well as the transverse impedance Z/sub T/ for the 20 TeV Superconducting Super Collider (SSC). Effects due to space charge, wall resistivity, bellows, monitor plates, synchrotron radiation are considered. The resulting Z/sub L//n and Z/sub T/ are plotted. Such a knowledge of Z/sub L//n and Z/sub T/ is necessary in computing the limits of many types of instabilities for the bunched beam. To be more specific, in our estimation, we consider the special case of an injection energy of 1 TeV and assume a maximum field of 5 Tesla in the SSC dipoles. In some cases, we also assume a 60 0 FODO cell structure consisting of 4 dipoles and 2 quadrupoles each with 2 long straight sections. The beampipe radius and beam radius are chosen as b = 1.0 in. and a = 0.05 cm respectively. Totally, the storage ring consists of 364 cells and has a mean radius of R = 17.38 km. Our results show that when monitor plates matched at both ends (such as the ones used in the Tevatron) are used, their effects dominate both Z/sub L//n and Z/sub T. 7 references, 5 figures

Electrochemical Impedance Spectroscopy Of Metal Alloys

Science.gov (United States)

Macdowell, L. G.; Calle, L. M.

1993-01-01

Report describes use of electrochemical impedance spectroscopy (EIS) to investigate resistances of 19 alloys to corrosion under conditions similar to those of corrosive, chloride-laden seaside environment of Space Transportation System launch site. Alloys investigated: Hastelloy C-4, C-22, C-276, and B-2; Inconel(R) 600, 625, and 825; Inco(R) G-3; Monel 400; Zirconium 702; Stainless Steel 304L, 304LN, 316L, 317L, and 904L; 20Cb-3; 7Mo+N; ES2205; and Ferralium 255. Results suggest electrochemical impedance spectroscopy used to predict corrosion performances of metal alloys.

Inductance analyzer based on auto-balanced circuit for precision measurement of fluxgate impedance

Science.gov (United States)

Setiadi, Rahmondia N.; Schilling, Meinhard

2018-05-01

An instrument for fluxgate sensor impedance measurement based on an auto-balanced circuit has been designed and characterized. The circuit design is adjusted to comply with the fluxgate sensor characteristics which are low impedance and highly saturable core with very high permeability. The system utilizes a NI-DAQ card and LabVIEW to process the signal acquisition and evaluation. Some fixed reference resistances are employed for system calibration using linear regression. A multimeter HP 34401A and impedance analyzer Agilent 4294A are used as calibrator and validator for the resistance and inductance measurements. Here, we realized a fluxgate analyzer instrument based on auto-balanced circuit, which measures the resistance and inductance of the device under test with a small error and much lower excitation current to avoid core saturation compared to the used calibrator.

Preliminary Study on Evaluation of Impact Resistance Performance of Fiber Reinforced Concrete Walls

International Nuclear Information System (INIS)

Jin, Byeong Moo; Lee, Yun Seok; Kim, Young Jin; Jeon, Se Jin

2012-01-01

As the safety assessments of nuclear power plants for the hypothetical large civil aircraft crash should be made mandatory, studies on large aircraft-nuclear power plant impact analyses and assessments studies are actively in progress. For the safety assessment of nuclear power plants against large civil aircraft crash, it is practically impossible to conduct full-scale experiments. Therefore, analysis using general purpose numerical analysis program accompanied by scale model experiments and element experiments has been adopted for the safety assessment. The safety of nuclear power plants against large civil aircraft crash is able to be accomplished by enhancement of the impact resistance performance, such as increasing the wall thickness, increasing the strength of concrete and using the fiber reinforced concrete which is able to be acquired by relatively simple process of adding fibers to a concrete mix without significant change of design and construction. A research for the enhancement of impact resistance performance depending upon design parameters for fiber reinforced concrete, such as type of fibers and application rate, is in progress. In this study, before the safety assessment of nuclear power plants against large civil aircraft crash, we assess the impact resistance performance of concrete wall depending upon type of fibers and impact velocity of objects

Preliminary Study on Evaluation of Impact Resistance Performance of Fiber Reinforced Concrete Walls

Energy Technology Data Exchange (ETDEWEB)

Jin, Byeong Moo; Lee, Yun Seok; Kim, Young Jin [Daewoo E and C Co. Ltd., Suwon (Korea, Republic of); Jeon, Se Jin [Ajou University, Suwon (Korea, Republic of)

2012-05-15

As the safety assessments of nuclear power plants for the hypothetical large civil aircraft crash should be made mandatory, studies on large aircraft-nuclear power plant impact analyses and assessments studies are actively in progress. For the safety assessment of nuclear power plants against large civil aircraft crash, it is practically impossible to conduct full-scale experiments. Therefore, analysis using general purpose numerical analysis program accompanied by scale model experiments and element experiments has been adopted for the safety assessment. The safety of nuclear power plants against large civil aircraft crash is able to be accomplished by enhancement of the impact resistance performance, such as increasing the wall thickness, increasing the strength of concrete and using the fiber reinforced concrete which is able to be acquired by relatively simple process of adding fibers to a concrete mix without significant change of design and construction. A research for the enhancement of impact resistance performance depending upon design parameters for fiber reinforced concrete, such as type of fibers and application rate, is in progress. In this study, before the safety assessment of nuclear power plants against large civil aircraft crash, we assess the impact resistance performance of concrete wall depending upon type of fibers and impact velocity of objects

CORROSION RESISTANCE OF ORGANOMETALLIC COATING APLICATED IN FUEL TANKS USING ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY IN BIOFUEL – PART I

Directory of Open Access Journals (Sweden)

Milene Adriane Luciano

2014-10-01

Full Text Available Nowadays, the industry has opted for more sustainable production processes, and the planet has also opted for new energy sources. From this perspective, automotive tanks with organometallic coatings as well as a partial substitution of fossil fuels by biofuels have been developed. These organometallic coated tanks have a zinc layer, deposited by a galvanizing process, formed between the steel and the organometallic coating. This work aims to characterize the organometallic coating used in metal automotive tanks and evaluate their corrosion resistance in contact with hydrated ethyl alcohol fuel (AEHC. For this purpose, the resistance of all layers formed between Zinc and EEP steel and also the tin coated steel, which has been used for over thirty years, were evaluated. The technique chosen was the Electrochemical Impedance Spectroscopy. The results indicated an increase on the corrosion resistance when organometallic coatings are used in AEHC medium. In addition to that, these coatings allow an estimated 25% reduction in tanks production costs.

Variable-viscosity thermal hemodynamic slip flow conveying nanoparticles through a permeable-walled composite stenosed artery

Science.gov (United States)

Akbar, Noreen Sher; Tripathi, Dharmendra; Bég, O. Anwar

2017-07-01

This paper presents a mathematical model for simulating viscous, incompressible, steady-state blood flow containing copper nanoparticles and coupled heat transfer through a composite stenosed artery with permeable walls. Wall slip hydrodynamic and also thermal buoyancy effects are included. The artery is simulated as an isotropic elastic tube, following Joshi et al. (2009), and a variable viscosity formulation is employed for the flowing blood. The equations governing the transport phenomena are non-dimensionalized and the resulting boundary value problem is solved analytically in the steady state subject to physically appropriate boundary conditions. Numerical computations are conducted to quantify the effects of relevant hemodynamic, thermophysical and nanoscale parameters emerging in the model on velocity and temperature profiles, wall shear stress, impedance resistance and also streamline distributions. The model may be applicable to drug fate transport modeling with nanoparticle agents and also to the optimized design of nanoscale medical devices for diagnosing stenotic diseases in circulatory systems.

Acoustic impedance rhinometry (AIR): a technique for monitoring dynamic changes in nasal congestion

International Nuclear Information System (INIS)

Patuzzi, Robert; Cook, Alison

2014-01-01

We describe a simple and inexpensive method for monitoring nasal air flow resistance using measurement of the small-signal acoustic input impedance of the nasal passage, similar to the audiological measurement of ear drum compliance with acoustic tympanometry. The method requires generation of a fixed sinusoidal volume–velocity stimulus using ear-bud speakers, and an electret microphone to monitor the resultant pressure fluctuation in the nasal passage. Both are coupled to the nose via high impedance silastic tubing and a small plastic nose insert. The acoustic impedance is monitored in real-time using a laptop soundcard and custom-written software developed in LabView 7.0 (National Instruments). The compact, lightweight equipment and fast time resolution lends the technique to research into the small and rapid reflexive changes in nasal resistance caused by environmental and local neurological influences. The acoustic impedance rhinometry technique has the potential to be developed for use in a clinical setting, where the need exists for a simple and inexpensive objective nasal resistance measurement technique. (paper)

Interdigitated electrodes as impedance and capacitance biosensors: A review

Science.gov (United States)

Mazlan, N. S.; Ramli, M. M.; Abdullah, M. M. A. B.; Halin, D. S. C.; Isa, S. S. M.; Talip, L. F. A.; Danial, N. S.; Murad, S. A. Z.

2017-09-01

Interdigitated electrodes (IDEs) are made of two individually addressable interdigitated comb-like electrode structures. IDEs are one of the most favored transducers, widely utilized in technological applications especially in the field of biological and chemical sensors due to their inexpensive, ease of fabrication process and high sensitivity. In order to detect and analyze a biochemical molecule or analyte, the impedance and capacitance signal need to be obtained. This paper investigates the working principle and influencer of the impedance and capacitance biosensors. The impedance biosensor depends on the resistance and capacitance while the capacitance biosensor influenced by the dielectric permittivity. However, the geometry and structures of the interdigitated electrodes affect both impedance and capacitance biosensor. The details have been discussed in this paper.

Feedback and rotational stabilization of resistive wall modes in ITER

International Nuclear Information System (INIS)

Liu Yueqiang; Bondeson, A.; Chu, M.S.; La Haye, R.J.; Favez, J.-Y.; Lister, J.B.; Gribov, Y.; Gryaznevich, M.; Hender, T.C.; Howell, D.F.

2005-01-01

Different models have been introduced in the stability code MARS-F in order to study the damping effect of resistive wall modes (RWM) in rotating plasmas. Benchmark of MARS-F calculations with RWM experiments on JET and D3D indicates that the semi-kinetic damping model is a good candidate for explaining the damping mechanisms. Based on these results, the critical rotation speeds required for RWM stabilization in an advanced ITER scenario are predicted. Active feedback control of the n = 1 RWM in ITER is also studied using the MARS-F code. (author)

Development on electromagnetic impedance function modeling and its estimation

Energy Technology Data Exchange (ETDEWEB)

Sutarno, D., E-mail: Sutarno@fi.itb.ac.id [Earth Physics and Complex System Division Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung (Indonesia)

2015-09-30

Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition

Multi-Electrode Impedance Method for Detection of Regional Ventilation

International Nuclear Information System (INIS)

Furuya, Norio; Sakamoto, Katsuyuki

2013-01-01

By means of computer simulation and experiment, we investigated the feasibility of simultaneously measuring the transfer impedance changes in the right apex, left apex, right base and left base of the lungs using the multi-electrode impedance method. To obtain the transfer impedance in each region, while suppressing the effects of other regions, changing the amplitude and polarity of the applied current must localize the high sensitivity areas in the interest region. Twelve current and eight voltage electrodes were equidistantly arranged on the anterior and posterior chest walls. The amplitudes and polarities of the currents that were simultaneously applied to the current electrodes, and which provided the appropriate sensitivity distribution, were theoretically obtained. The effects of the localized sensitivity distribution were verified by comparing the simulation results of the investigated method with the results of the conventional four-electrode method. From the results of the computer simulation, we developed a multi-electrode impedance pneumography and applied it to healthy adult volunteers who were both in sitting position and in left decubitus. We found that the measurement results were physiologically reasonable.

Polymer microchip impedance spectroscopy through two parallel planar embedded microelectrodes: Understanding the impedance contribution of the surrounding polymer on the measurement accuracy

International Nuclear Information System (INIS)

Kechadi, Mohammed; Gamby, Jean; Chaal, Lila; Girault, Hubert; Saidani, Boualem; Tribollet, Bernard

2013-01-01

The present work describes a new methodology for contact free impedance of a solution in a polymer microchip taking into account the role played by the surrounding polymer on the impedance accuracy. Measurements were carried out using a photoablated polyethylene terephthalate (PET) microchannel above two embedded microband electrodes. The impedance diagrams exhibit a loop from high frequencies to medium frequencies (1 MHz–100 Hz) and a capacitive behavior at low frequencies (100–1 Hz). The impedance diagrams were corrected by eliminating from the global microchip response the contribution of the impedance of the PET layer between the two microband electrodes. This operation enables a clear observation of the impedance in the microchannel solution, including the bulk solution contribution and the interfacial capacitance related to the surface roughness of the photoablated microchannel. Models for the impedance of solutions of varying conductivity showed that the capacitance of the polymer–solution interface can be modeled by a constant phase element (CPE) with an exponent of 0.5. The loop diameter was found to be proportional to the microchannel resistivity, allowing a cell constant around 4.93 × 10 5 m −1 in contactless microelectrodes configuration

Antimicrobial activity of Manuka honey against antibiotic-resistant strains of the cell wall-free bacteria Ureaplasma parvum and Ureaplasma urealyticum.

Science.gov (United States)

Hillitt, K L; Jenkins, R E; Spiller, O B; Beeton, M L

2017-03-01

The susceptibility of the cell wall-free bacterial pathogens Ureaplasma spp. to Manuka honey was examined. The minimum inhibitory concentration (MIC) of Manuka honey for four Ureaplasma urealyticum and four Ureaplasma parvum isolates was determined. Sensitivity to honey was also compared to clinical isolates with resistance to tetracycline, macrolide and fluoroquinolone antibiotics. Finally step-wise resistance training was utilized in an attempt to induce increased tolerance to honey. The MIC was dependent on the initial bacterial load with 7·5 and 18·0% w/v honey required to inhibit U. urealyticum at 1 and 10 6 colour changing units (CCU), respectively, and 4·8 and 15·3% w/v required to inhibit U. parvum at 1 and 10 6  CCU respectively. MIC values were consistently lower for U. parvum compared with U. urealyticum. Antimicrobial activity was seen against tetracycline-resistant, erythromycin-resistant and ciprofloxacin-resistant isolates at 10 5  CCU. No resistance to honey was observed with 50 consecutive challenges at increasing concentrations of honey. This is the first report of the antimicrobial activity of Manuka honey against a cell wall-free bacterial pathogen. The antimicrobial activity was retained against antibiotic-resistant strains and it was not possible to generate resistant mutants. Manuka honey is known to have a broad spectrum of antimicrobial activity, with the bacterial cell wall being suggested as a predominant site of action. This study has demonstrated that Manuka honey has activity against Ureaplasma spp., a genus of cell wall-free bacteria which are intrinsically resistant to many available antibiotics making treatment inherently difficult. This is the first report of the antimicrobial activity of Manuka honey against a bacterial pathogen, in the absence of a cell well and opens scope for the use of components of Manuka honey as a therapeutic among Ureaplasma infections. © 2016 The Society for Applied Microbiology.

Impedance response characteristics of iron oxide interface in the EDTA solutions

International Nuclear Information System (INIS)

Sawa, Tosio; Higuchi, Shigeo; Kataoka, Ichiro; Ito, Hisao.

1986-01-01

The relationship between the dissolution and the surface conditions of Fe 3 O 4 were studied in the various conditions of EDTA solutions by means of the A · C impedance measurement. From the experimental results obtained, surface layer of Fe 3 O 4 electrode can be expressed with electrical equivalent circuit that have capacitance and reaction resistance in the electrical double layer. In the Na 2 SO 4 solution without occuring dissolution, reaction resistance was estimated as 314 kΩ · cm 2 and capacitance was 203 μF/cm 2 . In the EDTA solutions, reaction resistance decreases along with dissolution of Fe 3 O 4 . The factors to make decrease reaction resistance are EDTA concentration, pH and temperature of the solutions. In contrast with this, the factor to increase it is dissolved oxygen in the solutions. The reciprocal value of reaction resistance agrees well with the rate of dissolution. On the other hand, when the electrode potential was maintained under the cathodic polarization in the EDTA solutions, impedances of electrode surface showed the lower value than that in the immersion condition. And apparent resistance came near to 0 at the potential of -2.0 V in all the range of frequency. Fe 3 O 4 electrodes pretreated with the cathodic polarization exhibited the characteristic impedance response that were caused by the change of electrode surface and the deposites such as iron hydroxide. (author)

Accumulated lipids rather than the rigid cell walls impede the extraction of genetic materials for effective colony PCRs in Chlorella vulgaris

Science.gov (United States)

2013-01-01

Background Failure of colony PCRs in green microalga Chlorella vulgaris is typically attributed to the difficulty in disrupting its notoriously rigid cell walls for releasing the genetic materials and therefore the development of an effective colony PCR procedure in C. vulgaris presents a challenge. Results Here we identified that colony PCR results were significantly affected by the accumulated lipids rather than the rigid cell walls of C. vulgaris. The higher lipids accumulated in C. vulgaris negatively affects the effective amplification by DNA polymerase. Based on these findings, we established a simple and extremely effective colony PCR procedure in C. vulgaris. By simply pipetting/votexing the pellets of C. vulgaris in 10 ul of either TE (10 mM Tris/1 mM EDTA) or 0.2% SDS buffer at room temperature, followed by the addition of 10 ul of either hexane or Phenol:Chloroform:Isoamyl Alcohol in the same PCR tube for extraction. The resulting aqueous phase was readily PCR-amplified as genomic DNA templates as demonstrated by successful amplification of the nuclear 18S rRNA and the chloroplast rbcL gene. This colony PCR protocol is effective and robust in C. vulgaris and also demonstrates its effectiveness in other Chlorella species. Conclusions The accumulated lipids rather than the rigid cell walls of C. vulgaris significantly impede the extraction of genetic materials and subsequently the effective colony PCRs. The finding has the potential to aid the isolation of high-quality total RNAs and mRNAs for transcriptomic studies in addition to the genomic DNA isolation in Chlorella. PMID:24219401

Thermal resistance of buffer layer in a ceramic wall of MHD generation channel

International Nuclear Information System (INIS)

Nomura, Osami; Ebata, Yoshihiro; Hijikata, Kenichi.

1982-01-01

A wal l model is composed for obtaining the thermal resistance of the buffer layer. A buffer layer of the model is consisted to an adhesive layer and a buffer body. The adhesive layer is made of a copper plate, which is 0.3 mm thick, and adhered to the element by Refractory Method. The adhesive layer is consisted to three layers, i.e., Cu, Cu 2 O and CuO. These three layers seems to give rise to the thermal resistance. The buffer body is made of nickel wires of which radious is 0.4 mm and purity is 99.7%. All of the nickel wires are assembled in one direction which is parallel to a center line of the element, and bundled all together. Occupation ratio of nickel is about 78% in a sectional area of the buffer body. One end of the buffer body is soldered to adhesive layer by silver solder and opposite and is soldered to holder by lead solder. An element of the model is made of magnesia ceramics of which purity is about 99.9% and porosity is about 3%. A holder of the model is made of copper block. Results are as follows: (1) Thermal resistance of the buffer layer is from 1.9 to 2.5K/(W/cm 2 ). (2) Thermal resistance of the adhesive layer is from 0.43 to 0.87K/(W/cm 2 ). (3) Thermal resistance of the buffer body is calculated to about 0.7K/(W/cm 2 ) under the estimation at which the heat flows in the nickel wires only. (4) From above results, thermal resistance of silver soldering layer seems to be same as that of the adhesive layers. The buffer layer needs more value of the thermal resistance in order to apply to the MHD generation channel. Value of the thermal resistance is easily satisfied by changing of material of the buffer body, increase of thickness of the buffer layer and etc. Then this wall appears to be useful to an MHD generation channel wall. (author)

Longitudinal coupling impedance of a thick iris collimator

International Nuclear Information System (INIS)

Gluckstern, R.L.; Jiang, S.

1992-01-01

A previous calculation of the longitudinal coupling impedance of an iris in a beam pipe turned out not to be well convergent. In this work an alternate basis vector for the matrix equations is constructed, leading to convergent results. Numerical results are presented for the limit a/b → ∞, corresponding to a beam passing through a circular hole in a thick wall. 4 figs., 4 refs

A simple toroidal shell model for the study of feedback stabilization of resistive wall modes in a tokamak plasma

International Nuclear Information System (INIS)

Jhang, Hogun

2008-01-01

A study is conducted on the feedback stabilization of resistive wall modes (RWMs) in a tokamak plasma using a toroidal shell model. An analytically tractable form of the RWM dispersion relation is derived in the presence of a set of discrete feedback coil currents. A parametric study is carried out to optimize the feedback system configuration. It is shown that the total toroidal angle of a resistive wall spanned by the feedback coils and the poloidal angular extent of a feedback coil are crucial parameters to determine the efficacy of the feedback system

Microwave effective surface impedance of structures including a high-Tc superconducting film

International Nuclear Information System (INIS)

Hartemann, P.

1992-01-01

The microwave effective surface impedances of different stacks made of high-temperature superconducting films, dielectric materials and bulk normal metals were computed. The calculations were based on the two-fluid model of superconductors and the conventional transmission line theory. These effective impedances are compared to the calculated intrinsic surface impedances of the stacked superconducting films. The considered superconducting material has been the oxide YBa 2 Cu 3 O 7 epitaxially grown on crystalline substrates (MgO, LaAlO 3 , SrTiO 3 ), the film thickness ranging from a few nm to 1μm. Discrepancies between the effective surface resistances or reactances and the corresponding intrinsic values were determined at 10 GHz for non resonant or resonant structures. At resonance the surface resistance discrepancy exhibits a sharp peak which reaches 10 4 or more in relative value according to the geometry and the used materials. Obviously the effective surface reactance shows also huge variations about the resonance and may be negative. Moreover geometries allowing to obtain an effective resistance smaller than the film intrinsic value have been found. The effects of the resonance phenomenon on the electromagnetic wave reflectivity and reflection phase shift are investigated. Therefore the reported theoretical results demonstrate that the effective surface impedance of YBCO films with a thickness smaller than 500 nm can be very different from the intrinsic film impedance according to the structures. (Author). 3 refs., 10 figs., 2 tabs

Electrode-less measurement of cell layers impedance

Czech Academy of Sciences Publication Activity Database

Krůšek, Jan; Ďaďo, S.

2014-01-01

Roč. 63, č. 6 (2014), s. 705-711 ISSN 0862-8408 R&D Projects: GA ČR(CZ) GBP304/12/G069 Institutional support: RVO:67985823 Keywords : cell impedance measurement * transepithelial resistance Subject RIV: ED - Physiology Impact factor: 1.293, year: 2014

Optical and impedance characteristics of passive films on pure aluminium

International Nuclear Information System (INIS)

Krishnakumar, R.; Szklarska-Smialowska, Z.

1992-01-01

Optical and Impedance behavior of pure bulk aluminum and pure sputtered aluminum film were studied in order to gain a better understanding of their fundamental passivation and pitting characteristics. Constant potential experiments at the passivation and pitting potentials, and potentiostatic anodic polarization were conducted while simultaneously monitoring the current, impedance and optical behavior, in-situ. Noise characteristics in the current data during the pit incubation period indicate that Cl - ions migrate with little impediment to the metal surface through defects in the passive film. Impedance experiments indicate that the polarization resistance fluctuates continuously with time during the pit incubation period, suggesting that impedance spectroscopy is sensitive to localized processes. The interfacial capacitance increases continuously during this time. The smallest pits observed on the sample surface (less than 10μ) are clearly crystallographic, indicating activation controlled dissolution at pits. The film capacitance increases with exposure time at the passivation potential, while the polarization resistance decreases continuously. The decrease in the film resistance is thought to be due to chloride incorporation at defects in the passive film. The increase in film capacitance at the passivation and pitting potential is due to an increase in the film dielectric constant caused by either a compositional change or anion incorporation. Ellipsometry results indicate growth of a dual layered film on the pure aluminum surface, with the outer layer probably containing varying amounts of incorporated chloride depending on the applied potential. Preliminary experiments indicate that in the case of sputtered aluminum film, the passive film resistance is at least an order of magnitude higher than that of bulk aluminum. This is due to the fine grain structure of sputtered Al and hence a more defect free passive film than that formed on bulk aluminum. There is

Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes

KAUST Repository

Ruffo, Riccardo

2009-07-02

The impedance behavior of silicon nanowire electrodes has been investigated to understand the electrochemical process kinetics that influences the performance when used as a high-capacity anode in a lithium ion battery. The ac response was measured by using impedance spectroscopy in equilibrium conditions at different lithium compositions and during several cycles of charge and discharge in a half cell vs. metallic lithium. The impedance analysis shows the contribution of both surface resistance and solid state diffusion through the bulk of the nanowires. The surface process is dominated by a solid electrolyte layer (SEI) consisting of an inner, inorganic insoluble part and several organic compounds at the outer interface, as seen by XPS analysis. The surface resistivity, which seems to be correlated with the Coulombic efficiency of the electrode, grows at very high lithium contents due to an increase in the inorganic SEI thickness. We estimate the diffusion coefficient of about 2 × 10 -10 cm 2/s for lithium diffusion in silicon. A large increase in the electrode impedance was observed at very low lithium compositions, probably due to a different mechanism for lithium diffusion inside the wires. Restricting the discharge voltage to 0.7 V prevents this large impedance and improves the electrode lifetime. Cells cycled between 0.07 and 0.70 V vs. metallic lithium at a current density of 0.84 A/g (C/5) showed good Coulombic efficiency (about 99%) and maintained a capacity of about 2000 mAh/g after 80 cycles. © 2009 American Chemical Society.

The local domain wall position in ferromagnetic thin wires: simultaneous measurement of resistive and transverse voltages at multiple points

International Nuclear Information System (INIS)

Hanada, R.; Sugawara, H.; Aoki, Y.; Sato, H.; Shigeto, K.; Shinjo, T.; Ono, T.; Miyajima, H.

2002-01-01

We have simultaneously measured the field dependences of voltages at multiple pairs of resistance and transverse voltage probes in ferromagnetic wires (with either magnetic or non-magnetic voltage probes). Both the resistive (through the giant magnetoresistance and anisotropic magnetoresistance) and transverse voltages (through the planar Hall effect) exhibit abrupt jumps, reflecting discrete motion of domain walls or rotations of magnetization. Voltage probes, even if non-magnetic, are found to affect the jump fields depending on the sample conditions. We demonstrate that the specific information on the domain (wall) motion along a thin ferromagnetic wire could be obtained from the jump fields. (author)

Characterization of lithium-thionyl chloride cells by impedance techniques

Science.gov (United States)

Walsh, F.; Pozin, M.; Cherniy, A.; Tikhonov, K.

The main contributor to voltage drop observed on initial discharge of lithium-thionyl chloride cells is the resistance of the passive layer on the lithium anode, as can be determined from the Nyquist plot of a lithium-thionyl chloride cell. At extremely low discharge currents, initial voltage drop corresponds to the value found from the impedance measurements; at higher current, an empirical correction based on the experimental results is required. The dispersion in the values of the impedance parameters and thus in initial voltage drop of individual cells was analyzed. The condition of the lithium surface after assembly was shown not to be the only reason for high dispersion in impedance parameter values.

Real-time imaging of cerebral infarction in rabbits using electrical impedance tomography.

Science.gov (United States)

Yang, Bin; Shi, Xuetao; Dai, Meng; Xu, Canhua; You, Fushen; Fu, Feng; Liu, Ruigang; Dong, Xiuzhen

2014-02-01

To investigate the possible use of electrical impedance tomography (EIT) in monitoring focal cerebral infarction in a rabbit model. A model of focal cerebral infarction was established in eight New Zealand rabbits using a photochemical method without craniectomy. Focal cerebral infarction was confirmed by histopathological examination. Intracranial impedance variation was measured using 16 electrodes placed in a circle on the scalp. EIT images were obtained using a damped least-squares reconstruction algorithm. The average resistivity value (ARV) of the infarct region on EIT images was calculated to quantify relative resistivity changes. A symmetry index was calculated to evaluate the relative difference in resistivity between the two sides of the cerebrum. EIT images and ARV curves showed that impedance changes caused by cerebral infarction increased linearly with irradiation time. A difference in ARV was found between measurements taken before and after infarct induction. Focal cerebral infarction can be monitored by EIT in the proposed animal model. The results are sufficiently encouraging that the authors plan to extend this study to humans, after further technical improvements.

Electrochemical Impedance Spectroscopy Illuminating Performance Evolution of Porous Core–Shell Structured Nickel/Nickel Oxide Anode Materials

International Nuclear Information System (INIS)

Yan, Bo; Li, Minsi; Li, Xifei; Bai, Zhimin; Dong, Lei; Li, Dejun

2015-01-01

Highlights: • The electrochemical reaction kinetics of the Ni/NiO anode was studied for the first time. • Charge transfer resistance is main contribution to total resistance during discharge process. • The slow growth of the SEI film is responsible for the capacity fading upon cycling. • Some promising strategies to optimize NiO anode performance were summarized. - Abstract: The electrochemical reaction kinetics of the porous core–shell structured Ni/NiO anode for Li ion battery application is systematically investigated by monitoring the electrochemical impedance evolution for the first time. The electrochemical impedance under prescribed condition is measured by using impedance spectroscopy in equilibrium conditions at various depths of discharge (DOD) during charge–discharge cycles. The Nyquist plots of the binder-free porous Ni/NiO electrode are interpreted with a selective equivalent circuit composed of solution resistance, solid electrolyte interphase (SEI) film, charge transfer and solid state diffusion. The impedance analysis shows that the change of charge transfer resistance is the main contribution to the total resistance change during discharge, and the surface configuration of the obtained electrode may experience significant change during the first two cycles. Meanwhile, the increase of internal resistance reduced the utilization efficiency of the active material may be another convincing factor to increase the irreversible capacity. In addition, the impedance evolution of the as-prepared electrode during charge–discharge cycles reveals that the slow growth of the SEI film is responsible for the capacity fading after long term cycling. As a result, several strategies are summarized to optimize the electrochemical performances of transition metal oxide anodes for lithium ion batteries

The Resistive Wall Mode Feedback Control System on DIII-D

International Nuclear Information System (INIS)

J.T. Scoville; D.H. Kellman; S.G.E. Pronko; A. Nerem; R. Hatcher; D. O'Neill; G. Rossi; M. Bolha

1999-01-01

One of the primary instabilities limiting the performance of the plasma in advanced tokamak operating regimes is the resistive wall mode (RWM) [1]. The most common RWM seen in the DIII-D tokamak is originated by an n=1 ideal external kink mode which, in the presence of a resistive wall, is converted to a slowly growing RWM. The mode causes a reduction in plasma rotation, a loss of stored energy, and sometimes leads to plasma disruption. It routinely limits the performance of a tokamak operating near reactor relevant parameter levels. A system designed to actively control the RWM has recently been installed on the DIII-D tokamak for the control of low m n=1 modes. In initial experiments, the control system has been capable of delaying the onset of RWMs in energetic discharges for several hundred milliseconds. The feedback control system consists of detector coils connected via control software to high power current amplifiers driving the excitation coils. The three pairs of excitation coils are each driven by a current amplifier and a DC power supply. The control signal is derived from a set of six sensor coils that measure radial flux as low as one Gauss. The signals are digitally processed by realtime software in the DIII-D Plasma Control System (PCS) to create a command that is sent to the current amplifier, with a cycle time of approximately 100 micros. The amplifiers, designed and fabricated by Robicon Corporation to a specification developed by PPPL and GA, are bipolar devices capable of ±5 kA at 300 V, with an operating bandwidth of approximately 800 Hz (-3 dB)

Reduced critical rotation for resistive-wall mode stabilization in a near-axisymmetric configuration.

Science.gov (United States)

Reimerdes, H; Garofalo, A M; Jackson, G L; Okabayashi, M; Strait, E J; Chu, M S; In, Y; La Haye, R J; Lanctot, M J; Liu, Y Q; Navratil, G A; Solomon, W M; Takahashi, H; Groebner, R J

2007-02-02

Recent DIII-D experiments with reduced neutral beam torque and minimum nonaxisymmetric perturbations of the magnetic field show a significant reduction of the toroidal plasma rotation required for the stabilization of the resistive-wall mode (RWM) below the threshold values observed in experiments that apply nonaxisymmetric magnetic fields to slow the plasma rotation. A toroidal rotation frequency of less than 10 krad/s at the q=2 surface (measured with charge exchange recombination spectroscopy using C VI) corresponding to 0.3% of the inverse of the toroidal Alfvén time is sufficient to sustain the plasma pressure above the ideal MHD no-wall stability limit. The low-rotation threshold is found to be consistent with predictions by a kinetic model of RWM damping.

Normal mode approach to modelling of feedback stabilization of the resistive wall mode

International Nuclear Information System (INIS)

Chu, M.S.; Chance, M.S.; Okabayashi, M.; Glasser, A.H.

2003-01-01

Feedback stabilization of the resistive wall mode (RWM) of a plasma in a general feedback configuration is formulated in terms of the normal modes of the plasma-resistive wall system. The growth/damping rates and the eigenfunctions of the normal modes are determined by an extended energy principle for the plasma during its open (feedback) loop operation. A set of equations are derived for the time evolution of these normal modes with currents in the feedback coils. The dynamics of the feedback system is completed by the prescription of the feedback logic. The feasibility of the feedback is evaluated by using the Nyquist diagram method or by solving the characteristic equations. The elements of the characteristic equations are formed from the growth and damping rates of the normal modes, the sensor matrix of the perturbation fluxes detected by the sensor loops, the excitation matrix of the energy input to the normal modes by the external feedback coils, and the feedback logic. (The RWM is also predicted to be excited by an external error field to a large amplitude when it is close to marginal stability.) This formulation has been implemented numerically and applied to the DIII-D tokamak. It is found that feedback with poloidal sensors is much more effective than feedback with radial sensors. Using radial sensors, increasing the number of feedback coils from a central band on the outboard side to include an upper and a lower band can substantially increase the effectiveness of the feedback system. The strength of the RWM that can be stabilized is increased from γτ w = 1 to 30 (γ is the growth rate of the RWM in the absence of feedback and τ w is the resistive wall time constant) Using poloidal sensors, just one central band of feedback coils is sufficient for the stabilization of the RWM with γτ w = 30. (author)

Single beam collective effects in FCC-ee due to beam coupling impedance

CERN Document Server

Belli, Eleonora; Persichelli, Serena; Zobov, Mikhail

2016-01-01

The Future Circular Collider study, hosted by CERN to design post-LHC particle accelerator options in a worldwide context, is focused on proton-proton high-energy and electron-positron high-luminosity frontier machines. This new accelerator complex represents a great challenge under several aspects, which involve R&D on beam dynamics and new technologies. One very critical point in this context is represented by collective effects, generated by the interaction of the beam with self-induced electromagnetic fields, called wake fields, which could produce beam instabilities, thus reducing the machines performance and limiting the maximum stored current. It is therefore very important to be able to predict these effects and to study in detail potential solutions to counteract them. In this paper the resistive wall and some other important geometrical sources of impedance for the FCC electron-positron accelerator are identified and evaluated, and their impact on the beam dynamics, which in some cases could lea...

Single beam collective effects in FCC-ee due to beam coupling impedance

CERN Document Server

Belli, Eleonora

2016-01-01

The Future Circular Collider study, hosted by CERN to design post-LHC particle accelerator options in a worldwide context, is focused on proton-proton high-energy and electron-positron high-luminosity frontier machines. This new accelerator complex represents a great challenge under several aspects, which involve R&D on beam dynamics and new technologies. One very critical point in this context is represented by collective effects, generated by the interaction of the beam with self-induced electromagnetic fields, called wake fields, which could produce beam instabilities, thus reducing the machines performance and limiting the maximum stored current. It is therefore very important to be able to predict these effects and to study in detail potential solutions to counteract them. In this paper the resistive wall and some other important geometrical sources of impedance for the FCC electron-positron accelera- tor are identified and evaluated, and their impact on the beam dynamics, which in some cases could l...

New equivalent-electrical circuit model and a practical measurement method for human body impedance.

Science.gov (United States)

Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako

2015-01-01

Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance.

Physical understanding of the instability spectrum and the feedback control of resistive wall modes in reversed field pinch

International Nuclear Information System (INIS)

Wang, Z.R.; Guo, S.C.

2011-01-01

The cylindrical MHD model integrated with a feedback system is applied to the study of resistive wall mode (RWM) in reversed field pinch (RFP) plasmas. The model takes into account the compressibility, longitudinal flow, viscosity and resistive wall with a finite thickness. The study, via both analytical and numerical analyses, provides a physical understanding on the following subjects: firstly, on the nature of the instability spectrum of the RWM observed in RFP plasmas; specifically, the growth rates of the two groups of the RWMs (internally non-resonant and externally non-resonant) have opposite dependence on the variation of the field reversal. Secondly, on the response of the unstable plasmas to the feedback control in RFPs, the mode behaviour in plasmas under the feedback is clarified and discussed in detail. Finally, the linear solutions of time evolution of RWM instability in various feedback scenarios are given. The effects of the wall proximity, the sensor location and the system response time are discussed, respectively.

Results of polarization resistance and impedance of steel bars embedded in carbonated concrete contaminated with chlorides

International Nuclear Information System (INIS)

Andrade, C.; Alonso, C.; Gonzalez, J.A.

1989-01-01

Laboratory results of the corrosion rate of steel embedded in carbonated concrete contaminated with chlorides determined through the Polarization Resistance method are presented here as examples of the possibilities offered by this technique in order to monitor the reinforcement corrosion process. The Rp technique has the advantages of fast response, simple and relatively accurate. Contrasts with gravimetric losses are presented. The A.C. Impedance measurements determined on the same specimens are also presented. The difficulties found in the interpretation of the results are stressed. R T values cannot easily be obtained. Several electrical circuits which may model the behaviour of the steel/concrete system are discussed. Finally, comments on the basic criteria to interpret results of both techniques are given. (author) 4 refs., 6 figs

Structural and impedance spectroscopic studies of samarium modified lead zirconate titanate ceramics

Energy Technology Data Exchange (ETDEWEB)

Ranjan, Rajiv [Department of Physics, Jamshedpur Co-operative College, Jamshedpur 831036 (India); Kumar, Rajiv [Department of Physics, Jamshedpur Worker' s College, Jamshedpur 831012 (India); Behera, Banarji [Department of Physics and Meteorology, I.I.T. Kharagpur 721302 (India); Choudhary, R.N.P., E-mail: crnpfl@phy.iitkgp.ernet.i [Department of Physics and Meteorology, I.I.T. Kharagpur 721302 (India)

2009-11-01

The polycrystalline samples of Pb{sub 1-x}Sm{sub x}(Zr{sub 0.60}Ti{sub 0.40}){sub 1-x/4}O{sub 3} (PSZT) where x=0.00, 0.03, 0.06 and 0.09 were prepared by a high-temperature solid-state reaction technique. The preliminary structural analysis using X-ray diffraction (XRD) data collected at room temperature has confirmed the formation of single-phase compounds in tetragonal crystal system. The morphological study of each sample using scanning electron microscope (SEM) has revealed that the grains are uniformly distributed through out the surfaces of the samples. Using complex impedance spectroscopy (CIS) technique, the electrical impedance and modulus properties of the materials were studied in a wide range of temperatures at different frequencies. The impedance analysis indicates the presence of bulk resistive contributions in the materials which is found to decrease on increasing temperature. The nature of variation of resistances with temperature suggests a typical negative temperature coefficient of resistance (NTCR) type behavior of the materials. The complex modulus plots clearly exhibits the presence of grain boundaries along with the bulk contributions in the PSZT materials. The presence of non-Debye type of relaxation has been confirmed by the complex impedance analysis. The variation of dc conductivity (bulk) with temperature demonstrates that the compounds exhibit Arrhenius type of electrical conductivity.

Nitrogen fertilizer application affects lodging resistance by altering secondary cell wall synthesis in japonica rice (Oryza sativa).

Science.gov (United States)

Zhang, Wujun; Wu, Longmei; Ding, Yanfeng; Yao, Xiong; Wu, Xiaoran; Weng, Fei; Li, Ganghua; Liu, Zhenghui; Tang, She; Ding, Chengqiang; Wang, Shaohua

2017-09-01

Stem mechanical strength is an important agricultural quantitative trait that is closely related to lodging resistance in rice, which is known to be reduced by fertilizer with higher levels of nitrogen. To understand the mechanism that regulates stem mechanical strength in response to nitrogen, we analysed stem morphology, anatomy, mechanical properties, cell wall components, and expression of cell wall-related genes, in two varieties of japonica rice, namely, Wuyunjing23 (lodging-resistant variety) and W3668 (lodging-susceptible variety). The results showed that higher nitrogen fertilizer increased the lodging index in both varieties due to a reduction in breaking strength and bending stress, and these changes were larger in W3668. Cellulose content decreased slightly under higher nitrogen fertilizer, whereas lignin content reduced remarkably. Histochemical staining revealed that high nitrogen application decreased lignin deposition in the secondary cell wall of the sclerenchyma cells and vascular bundle cells compared with the low nitrogen treatments, while it did not alter the pattern of cellulose deposition in these cells in both Wuyunjing23 and W3668. In addition, the expression of the genes involved in lignin biosynthesis, OsPAL, OsCoMT, Os4CL3, OsCCR, OsCAD2, OsCAD7, OsCesA4, and OsCesA7, were also down-regulated under higher nitrogen conditions at the early stage of culm growth. These results suggest that the genes involved in lignin biosynthesis are down-regulated by higher nitrogen fertilizer, which causes lignin deficiency in the secondary cell walls and the weakening of mechanical tissue structure. Subsequently, this results in these internodes with reduced mechanical strength and poor lodging resistance.

Model-based control of the resistive wall mode in DIII-D: A comparison study

International Nuclear Information System (INIS)

Dalessio, J.; Schuster, E.; Humphreys, D.A.; Walker, M.L.; In, Y.; Kim, J.-S.

2009-01-01

One of the major non-axisymmetric instabilities under study in the DIII-D tokamak is the resistive wall mode (RWM), a form of plasma kink instability whose growth rate is moderated by the influence of a resistive wall. One of the approaches for RWM stabilization, referred to as magnetic control, uses feedback control to produce magnetic fields opposing the moving field that accompanies the growth of the mode. These fields are generated by coils arranged around the tokamak. One problem with RWM control methods used in present experiments is that they predominantly use simple non-model-based proportional-derivative (PD) controllers requiring substantial derivative gain for stabilization, which implies a large response to noise and perturbations, leading to a requirement for high peak voltages and coil currents, usually leading to actuation saturation and instability. Motivated by this limitation, current efforts in DIII-D include the development of model-based RWM controllers. The General Atomics (GA)/Far-Tech DIII-D RWM model represents the plasma surface as a toroidal current sheet and characterizes the wall using an eigenmode approach. Optimal and robust controllers have been designed exploiting the availability of the RWM dynamic model. The controllers are tested through simulations, and results are compared to present non-model-based PD controllers. This comparison also makes use of the μ structured singular value as a measure of robust stability and performance of the closed-loop system.

Pulmonary Vascular Input Impedance is a Combined Measure of Pulmonary Vascular Resistance and Stiffness and Predicts Clinical Outcomes Better than PVR Alone in Pediatric Patients with Pulmonary Hypertension

Science.gov (United States)

Hunter, Kendall S.; Lee, Po-Feng; Lanning, Craig J.; Ivy, D. Dunbar; Kirby, K. Scott; Claussen, Lori R.; Chan, K. Chen; Shandas, Robin

2011-01-01

Background Pulmonary vascular resistance (PVR) is the current standard for evaluating reactivity in children with pulmonary arterial hypertension (PAH). However, PVR measures only the mean component of right ventricular afterload and neglects pulsatile effects. We recently developed and validated an method to measure pulmonary vascular input impedance, which revealed excellent correlation between the zero-harmonic impedance value and PVR, and suggested a correlation between higher harmonic impedance values and pulmonary vascular stiffness (PVS). Here we show that input impedance can be measured routinely and easily in the catheterization laboratory, that impedance provides PVR and PVS from a single measurement, and that impedance is a better predictor of disease outcomes compared to PVR. Methods Pressure and velocity waveforms within the main PA were measured during right-heart catheterization of patients with normal PA hemodynamics (n=14) and those with PAH undergoing reactivity evaluation (49 subjects; 95 conditions). A correction factor needed to transform velocity into flow was obtained by calibrating against cardiac output. Input impedance was obtained off-line by dividing Fourier-transformed pressure and flow waveforms. Results Exceptional correlation was found between the indexed zero harmonic of impedance and indexed PVR (y=1.095·x+1.381, R2=0.9620). Additionally, the modulus sum of the first two harmonics of impedance was found to best correlate with indexed pulse pressure over stroke volume (PP/SV) (y=13.39·x-0.8058, R2=0.7962). Amongst a subset of PAH patients (n=25), cumulative logistic regression between outcomes to total indexed impedance was better (RL2=0.4012) than between outcomes and indexed PVR (RL2=0.3131). Conclusions Input impedance can be consistently and easily obtained from PW Doppler and a single catheter pressure measurement, provides comprehensive characterization of the main components of RV afterload, and better predicts patient

A multimode analytic cylindrical model for the stabilization of the resistive wall modes

International Nuclear Information System (INIS)

Miron, I G

2008-01-01

A dispersion relation concerning the stability of the resistive wall modes within a multimode cylindrical analytical model is presented. This paper generalizes the Fitzpatrick-Aydemir model (Fitzpatrick R and Aydemir A Y 1996 Nucl. Fusion 1 11) in the presence of an unlimited number of neighboring modes for a tokamak plasma column surrounded by a resistive shell and a feedback system consisting of a number of detector and active feedback coils. The model is applied to the HBT-EP tokamak (Cates C et al 2000 Phys. Plasmas 7 3133) with its peculiar feedback system disposal. Finally, an analytical dispersion relation is obtained that can be solved by using a simple MATLAB code

Impedance spectroscopy studies of surface engineered TiO2 ...

Indian Academy of Sciences (India)

Administrator

Impedance; nanoTiO2; self-assembled monolayers; electrical resistivity; permittivity. 1. Introduction ... search studies showed that nanostructured TiO2 ceramics possess ..... tion handbook (ed) J Cazes (New York: Marcel Dekker). 3rd ed, p ...

Beam impedance of ferrite kicker magnets

International Nuclear Information System (INIS)

Voelker, F.; Lambertson, G.

1989-03-01

We have measured the longitudinal beam impedance of a typical pulsed magnet that will be used in the Advanced Light Source. The magnets are of a ferrite window-frame design with a single plate conductor on each side. Two separate power supplies are used to drive current in opposite directions in the two conductors. The continuity of the ferrite yoke is interrupted by two copper plates 1 mm thick in the center of the top and bottom of the window frame. This increases the reluctance of the magnetic path, and thus decreases the flux which couples the beam. The measurements were made by exciting a 1/8'' rod along the beam path through the magnet. This makes a 185 ohm transmission line, and it was terminated in a resistive divider at the exit end. A 3 GHz network analyzer was used to measure S 21 through the magnet, and longitudinal beam impedance was calculated from this data. The impedance is dominated by two low frequency resonances in the magnet winding and drive current. 8 figs

Fire resistance of a steel plate reinforced concrete bearing wall

International Nuclear Information System (INIS)

Kodaira, Akio; Kanchi, Masaki; Fujinaka, Hideo; Akita, Shodo; Ozaki, Masahiko

2003-01-01

Samples from a steel plate reinforced concrete bearing wall composed of concrete slab sandwiched between studded steel plates, were subjected to loaded fire resistance tests. There were two types of specimens: some were 1800 mm high while the rest were 3000 mm high ; thickness and width were the same for all specimens, at 200 mm and 800 mm, respectively. Under constant load conditions, one side of each specimen was heated along the standard fire-temperature curve. The results enabled us to approximate the relationship between the ratio of working load to concrete strength N/(Ac x c σ b) and the fire resistance time (t: minutes), as equation (1) for the 1800 mm - high specimen, and equation (2) for the 3000 mm - high specimen. N/(Ac x c σ b) = 2.21 x (1/t) 0.323 (1), .N/(Ac x c σ b) 2.30 x (1/t) 0.378 (2) In addition, the temperature of the unheated side of the specimens was 100degC at 240 minutes of continuous heating, clearly indicating that there was sufficient heat insulation. (author)

Impedance spectroscopy of SrBi2Ta2O9 and SrBi2Nb2O9 ceramics correlation with fatigue behavior

International Nuclear Information System (INIS)

Chen, T.; Thio, C.; Desu, S.B.

1997-01-01

In this research, a fatigue model for ferroelectric materials is proposed. The reasons for the electrical fatigue resistance of SrBi 2 Ta 2 O 9 (SBT), SrBi 2 Nb 2 O 9 (SBN), and PbZr 1-x Ti x O 3 (PZT) are discussed in terms of the bulk ionic conductivities of the compounds. To obtain the bulk ionic conductivity of SBT and SBN, we have used impedance spectroscopy which provides an effective method that allows us to separate the individual contributions of bulk, grain boundaries, and electrode-ferroelectric interfaces from the total capacitor impedance. The bulk ionic conductivities of SBT and SBN (∼10 -7 S/cm) are much higher than those of the perovskite ferroelectrics, e.g., PZT (∼10 -11 -10 -10 S/cm). The high ionic conductivities led us to conclude that the good fatigue resistance of SrBi 2 Ta 2 O 9 and SrBi 2 Nb 2 O 9 is due to easy recovery of defects. Specifically, oxygen vacancies entrapped within the capacitors are easily released, resulting in limited space charge buildup and domain wall pinning during the polarization reversal process. However, the oxygen vacancies in PZT are trapped at trap sites to become space charges, resulting in capacitor fatigue. copyright 1997 Materials Research Society

[Abdomen specific bioelectrical impedance analysis (BIA) methods for evaluation of abdominal fat distribution].

Science.gov (United States)

Ida, Midori; Hirata, Masakazu; Hosoda, Kiminori; Nakao, Kazuwa

2013-02-01

Two novel bioelectrical impedance analysis (BIA) methods have been developed recently for evaluation of intra-abdominal fat accumulation. Both methods use electrodes that are placed on abdominal wall and allow evaluation of intra-abdominal fat area (IAFA) easily without radiation exposure. Of these, "abdominal BIA" method measures impedance distribution along abdominal anterior-posterior axis, and IAFA by BIA method(BIA-IAFA) is calculated from waist circumference and the voltage occurring at the flank. Dual BIA method measures impedance of trunk and body surface at the abdominal level and calculates BIA-IAFA from transverse and antero-posterior diameters of the abdomen and the impedance of trunk and abdominal surface. BIA-IAFA by these two BIA methods correlated well with IAFA measured by abdominal CT (CT-IAFA) with correlatipn coefficient of 0.88 (n = 91, p abdominal adiposity in clinical study and routine clinical practice of metabolic syndrome and obesity.

Cutting tool wear monitoring with the use of impedance layers

OpenAIRE

Sadílek, Marek; Kratochvíl, Jiří; Petrů, Jana; Čep, Robert; Zlámal, Tomáš; Stančeková, Dana

2014-01-01

The article deals with problems of cutting process monitoring in real time. It is focused on tool wear by means of impedance layers applied on ceramic cutting inserts. In the experimental part the cutting process is monitored using electrical resistance measurement. The results are compared and verified using the monitored cutting temperature and tool wear. The testing of impedance layers is reasonable mainly for cutting edge diagnostics. The width of this layer determines the wear allowance ...

Impeding hohlraum plasma stagnation in inertial-confinement fusion.

Science.gov (United States)

Li, C K; Séguin, F H; Frenje, J A; Rosenberg, M J; Rinderknecht, H G; Zylstra, A B; Petrasso, R D; Amendt, P A; Landen, O L; Mackinnon, A J; Town, R P J; Wilks, S C; Betti, R; Meyerhofer, D D; Soures, J M; Hund, J; Kilkenny, J D; Nikroo, A

2012-01-13

This Letter reports the first time-gated proton radiography of the spatial structure and temporal evolution of how the fill gas compresses the wall blowoff, inhibits plasma jet formation, and impedes plasma stagnation in the hohlraum interior. The potential roles of spontaneously generated electric and magnetic fields in the hohlraum dynamics and capsule implosion are discussed. It is shown that interpenetration of the two materials could result from the classical Rayleigh-Taylor instability occurring as the lighter, decelerating ionized fill gas pushes against the heavier, expanding gold wall blowoff. This experiment showed new observations of the effects of the fill gas on x-ray driven implosions, and an improved understanding of these results could impact the ongoing ignition experiments at the National Ignition Facility.

Electrical Impedance Spectroscopic Studies on Broiler Chicken Tissue Suitable for the Development of Practical Phantoms in Multifrequency EIT

Directory of Open Access Journals (Sweden)

Tushar Kanti Bera

2011-06-01

Full Text Available Phantoms are essential for assessing the system performance in Electrical Impedance Tomography (EIT. Saline phantoms with insulator inhomogeneity fail to mimic the physiological structure of real body tissue in several aspects. Saline or any other salt solutions are purely resistive and hence studying multifrequency EIT systems cannot be assessed with saline phantoms because the response of the purely resistive materials do not change over frequency. Animal tissues show a variable response over a wide band of signal frequency due to their complex physiological and physiochemical structures and hence they can suitably be used as bathing medium and inhomogeneity in the phantoms of multifrequency EIT system. An efficient assessment of a multifrequency EIT system with real tissue phantom needs a prior knowledge of the impedance profile of the bathing medium as well as the inhomogeneity. In this direction Electrical Impedance Spectroscopy (EIS of broiler chicken muscle tissue paste and broiler chicken fat tissue is conducted from 10 Hz to 2 MHz using an impedance analyzer and their impedance profiles are thoroughly studied. Results show that the broiler chicken muscle tissue paste is less resistive than the fat tissue and hence it can be successfully used as the bathing medium of the phantoms for resistivity imaging in multifrequency EIT. Fat tissue is found more resistive than the muscle tissue which makes it more suitable for the inhomogeneity in phantoms of resistivity imaging study. doi:10.5617/jeb.174 J Electr Bioimp, vol. 2, pp. 48-63, 2011

A Portable Impedance Immunosensing System for Rapid Detection of Salmonella Typhimurium.

Science.gov (United States)

Wen, Tao; Wang, Ronghui; Sotero, America; Li, Yanbin

2017-08-28

Salmonella Typhimurium is one of the most dangerous foodborne pathogens and poses a significant threat to human health. The objective of this study was to develop a portable impedance immunosensing system for rapid and sensitive detection of S . Typhimurium in poultry. The developed portable impedance immunosensing system consisted of a gold interdigitated array microelectrode (IDAM), a signal acquisitive interface and a laptop computer with LabVIEW software. The IDAM was first functionalized with 16-Mercaptohexadecanoic acid, and streptavidin was immobilized onto the electrode surface through covalent bonding. Then, biotin-labelled S . Typhimurium -antibody was immobilized onto the IDAM surface. Samples were dropped on the surface of the IDAM and the S . Typhimurium cells in the samples were captured by the antibody on the IDAM. This resulted in impedance changes that were measured and displayed with the LabVIEW software. An equivalent circuit of the immunosensor demonstrated that the largest change in impedance was due to the electron-transfer resistance. The equivalent circuit showed an increase of 35% for the electron-transfer resistance value compared to the negative control. The calibration result indicated that the portable impedance immunosensing system could be used to measure the standard impedance elements, and it had a maximum error of measurement of approximately 13%. For pure culture detection, the system had a linear relationship between the impedance change and the logarithmic value of S . Typhimurium cells ranging from 76 to 7.6 × 10⁶ CFU (colony-forming unit) (50 μL) -1 . The immunosensor also had a correlation coefficient of 0.98, and a high specificity for detection of S . Typhimurium cells with a limit of detection (LOD) of 10² CFU (50 μL) -1 . The detection time from the moment a sample was introduced to the display of the results was 1 h. To conclude, the portable impedance immunosensing system for detection of S . Typhimurium achieved

A Portable Impedance Immunosensing System for Rapid Detection of Salmonella Typhimurium

Directory of Open Access Journals (Sweden)

Tao Wen

2017-08-01

Full Text Available Salmonella Typhimurium is one of the most dangerous foodborne pathogens and poses a significant threat to human health. The objective of this study was to develop a portable impedance immunosensing system for rapid and sensitive detection of S. Typhimurium in poultry. The developed portable impedance immunosensing system consisted of a gold interdigitated array microelectrode (IDAM, a signal acquisitive interface and a laptop computer with LabVIEW software. The IDAM was first functionalized with 16-Mercaptohexadecanoic acid, and streptavidin was immobilized onto the electrode surface through covalent bonding. Then, biotin-labelled S. Typhimurium-antibody was immobilized onto the IDAM surface. Samples were dropped on the surface of the IDAM and the S. Typhimurium cells in the samples were captured by the antibody on the IDAM. This resulted in impedance changes that were measured and displayed with the LabVIEW software. An equivalent circuit of the immunosensor demonstrated that the largest change in impedance was due to the electron-transfer resistance. The equivalent circuit showed an increase of 35% for the electron-transfer resistance value compared to the negative control. The calibration result indicated that the portable impedance immunosensing system could be used to measure the standard impedance elements, and it had a maximum error of measurement of approximately 13%. For pure culture detection, the system had a linear relationship between the impedance change and the logarithmic value of S. Typhimurium cells ranging from 76 to 7.6 × 106 CFU (colony-forming unit (50 μL−1. The immunosensor also had a correlation coefficient of 0.98, and a high specificity for detection of S. Typhimurium cells with a limit of detection (LOD of 102 CFU (50 μL−1. The detection time from the moment a sample was introduced to the display of the results was 1 h. To conclude, the portable impedance immunosensing system for detection of S. Typhimurium

Electrical resisitivity of mechancially stablized earth wall backfill

Science.gov (United States)

Snapp, Michael; Tucker-Kulesza, Stacey; Koehn, Weston

2017-06-01

Mechanically stabilized earth (MSE) retaining walls utilized in transportation projects are typically backfilled with coarse aggregate. One of the current testing procedures to select backfill material for construction of MSE walls is the American Association of State Highway and Transportation Officials standard T 288: ;Standard Method of Test for Determining Minimum Laboratory Soil Resistivity.; T 288 is designed to test a soil sample's electrical resistivity which correlates to its corrosive potential. The test is run on soil material passing the No. 10 sieve and believed to be inappropriate for coarse aggregate. Therefore, researchers have proposed new methods to measure the electrical resistivity of coarse aggregate samples in the laboratory. There is a need to verify that the proposed methods yield results representative of the in situ conditions; however, no in situ measurement of the electrical resistivity of MSE wall backfill is established. Electrical resistivity tomography (ERT) provides a two-dimensional (2D) profile of the bulk resistivity of backfill material in situ. The objective of this study was to characterize bulk resistivity of in-place MSE wall backfill aggregate using ERT. Five MSE walls were tested via ERT to determine the bulk resistivity of the backfill. Three of the walls were reinforced with polymeric geogrid, one wall was reinforced with metallic strips, and one wall was a gravity retaining wall with no reinforcement. Variability of the measured resistivity distribution within the backfill may be a result of non-uniform particle sizes, thoroughness of compaction, and the presence of water. A quantitative post processing algorithm was developed to calculate mean bulk resistivity of in-situ backfill. Recommendations of the study were that the ERT data be used to verify proposed testing methods for coarse aggregate that are designed to yield data representative of in situ conditions. A preliminary analysis suggests that ERT may be utilized

Application of multi-walled carbon nanotubes to enhance anodic ...

African Journals Online (AJOL)

STORAGESEVER

2009-12-15

Dec 15, 2009 ... Key words: Multi-walled carbon nanotubes, microbial fuel cell, Enterobacter cloacae, ... Aldrich) was prepared in absolute ethanol (Hu et al., 2006; Tkac .... incorporated Eu3+ by voltammetry and electrochemical impedance.

Calculation of Coherent Synchrotron Radiation Impedance for a Beam Moving in a Curved Trajectory

Science.gov (United States)

Zhou, Demin; Ohmi, Kazuhito; Oide, Katsunobu; Zang, Lei; Stupakov, Gennady

2012-01-01

Coherent synchrotron radiation (CSR) fields are generated when a bunched beam moves along a curved trajectory. A new code, named CSRZ, was developed using finite difference method to calculate the longitudinal CSR impedance for a beam moving along a curved chamber. The method adopted in the code was originated by Agoh and Yokoya [Phys. Rev. ST Accel. Beams 7 (2004) 054403]. It solves the parabolic equation in the frequency domain in a curvilinear coordinate system. The chamber considered has uniform rectangular cross-section along the beam trajectory. The code was used to investigate the properties of CSR impedance of a single or a series of bending magnets. The calculation results indicate that the shielding effect due to outer chamber wall can be well explained by a simple optical approximation model at high frequencies. The CSR fields reflected by the outer wall may interfere with each other along a series of bending magnets and lead to sharp narrow peaks in the CSR impedance. In a small storage ring, such interference effect can be significant and may cause microwave instability, according to a simple estimate of instability threshold.

Bioelectrical impedance vector distribution in the first year of life.

Science.gov (United States)

Savino, Francesco; Grasso, Giulia; Cresi, Francesco; Oggero, Roberto; Silvestro, Leandra

2003-06-01

We assessed the bioelectrical impedance vector distribution in a sample of healthy infants in the first year of life, which is not available in literature. The study was conducted as a cross-sectional study in 153 healthy Caucasian infants (90 male and 63 female) younger than 1 y, born at full term, adequate for gestational age, free from chronic diseases or growth problems, and not feverish. Z scores for weight, length, cranial circumference, and body mass index for the study population were within the range of +/-1.5 standard deviations according to the Euro-Growth Study references. Concurrent anthropometrics (weight, length, and cranial circumference), body mass index, and bioelectrical impedance (resistance and reactance) measurements were made by the same operator. Whole-body (hand to foot) tetrapolar measurements were performed with a single-frequency (50 kHz), phase-sensitive impedance analyzer. The study population was subdivided into three classes of age for statistical analysis: 0 to 3.99 mo, 4 to 7.99 mo, and 8 to 11.99 mo. Using the bivariate normal distribution of resistance and reactance components standardized by the infant's length, the bivariate 95% confidence limits for the mean impedance vector separated by sex and age groups were calculated and plotted. Further, the bivariate 95%, 75%, and 50% tolerance intervals for individual vector measurements in the first year of life were plotted. Resistance and reactance values often fluctuated during the first year of life, particularly as raw measurements (without normalization by subject's length). However, 95% confidence ellipses of mean vectors from the three age groups overlapped each other, as did confidence ellipses by sex for each age class, indicating no significant vector migration during the first year of life. We obtained an estimate of mean impedance vector in a sample of healthy infants in the first year of life and calculated the bivariate values for an individual vector (95%, 75%, and 50

Electrochemical behavior of single-walled carbon nanotube supercapacitors under compressive stress.

Science.gov (United States)

Li, Xin; Rong, Jiepeng; Wei, Bingqing

2010-10-26

The effect of compressive stress on the electrochemical behavior of flexible supercapacitors assembled with single-walled carbon nanotube (SWNT) film electrodes and 1 M aqueous electrolytes with different anions and cations were thoroughly investigated. The under-pressed capacitive and resistive features of the supercapacitors were studied by means of cyclic voltammetry measurements and electrochemical impedance analysis. The results demonstrated that the specific capacitance increased first and saturated in corresponding decreases of the series resistance, the charge-transfer resistance, and the Warburg diffusion resistance under an increased pressure from 0 to 1723.96 kPa. Wettability as well as ion-size effect of different aqueous electrolytes played important roles to determine the pressure dependence behavior of the suerpcapacitors under an applied pressure. An improved high-frequency capacitive response with 1172 Hz knee frequency, which is significantly higher compared to reported values, was observed under the compressive pressure of 1723.96 kPa, indicating an improving and excellent high-power capability of the supercapacitors under the pressure. The experimental results and the thorough analysis described in this work not only provide fundamental insight of pressure effects on supercapacitors but also give an important guideline for future design of next generation flexible/stretchable supercapacitors for industrial and consumer applications.

Quantum dots conjugated zinc oxide nanosheets: Impeder of microbial growth and biofilm

Science.gov (United States)

Patil, Rajendra; Gholap, Haribhau; Warule, Sambhaji; Banpurkar, Arun; Kulkarni, Gauri; Gade, Wasudeo

2015-01-01

The grieving problem of the 21st century has been the antimicrobial resistance in pathogenic microorganisms to conventional antibiotics. Therefore, developments of novel antibacterial materials which effectively inhibit or kill such resistant microorganisms have become the need of the hour. In the present study, we communicate the synthesis of quantum dots conjugated zinc oxide nanostructures (ZnO/CdTe) as an impeder of microbial growth and biofilm. The as-synthesized nanostructures were characterized by X-ray diffraction, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, field emission scanning electron microscopy and high resolution transmission electron microscopy. The growth impedance property of ZnO and ZnO/CdTe on Gram positive organism, Bacillus subtilis NCIM 2063 and Gram negative, Escherichia coli NCIM 2931 and biofilm impedance activity in Pseudomonas aeruginosa O1 was found to occur due to photocatalytical action on the cell biofilm surfaces. The impedance in microbial growth and biofilm formation was further supported by ruptured appearances of cells and dettrered biofilm under field emission scanning electron and confocal laser scanning microscope. The ZnO/CdTe nanostructures array synthesized by hydrothermal method has an advantage of low growth temperature, and opportunity to fabricate inexpensive material for nano-biotechnological applications.

Characterization of Porous WO3 Electrochromic Device by Electrochemical Impedance Spectroscopy

Directory of Open Access Journals (Sweden)

Chien Chon Chen

2013-01-01

Full Text Available This paper concerns the microstructure of the anodic tungsten oxide (WO3 and its use in an electrochromic (EC glass device. When voltages between 100 V and 160 V were applied to tungsten film for 1 h under 0.4 wt. % NaF electrolyte, porous WO3 film was formed. The film, which had a large surface area, was used as electrochromic film for EC glass. The average transmittance in a visible region of the spectrum for a 144 cm2 EC device was above 75% in the bleached state and below 40% in the colored state, respectively. Repeatability using of the colored/bleached cycles was tested good by a cyclic voltammograms method. The internal impedance values under colored and bleached states were detected and simulated using an electrical impedance spectra (EIS technique. The EC glass impedance characteristics were simulated using resistors, capacitors, and Warburg impedance. The ITO/WO3, WO3/electrolyte, electrolyte/NiO, and NiO/ITO interfaces can be simulated using a resistance capacitance (RC parallel circuits, and bulk materials such as the indium tin oxide (ITO and conducting wire can be simulated by using a series of resisters.

Acoustic impedances of ear canals measured by impedance tube

DEFF Research Database (Denmark)

Ciric, Dejan; Hammershøi, Dorte

2007-01-01

During hearing sensitivity tests, the sound field is commonly generated by an earphone placed on a subject ear. One of the factors that can affect the sound transmission in the ear is the acoustic impedance of the ear canal. Its importance is related to the contribution of other elements involved...... in the transmission such as the earphone impedance. In order to determine the acoustic impedances of human ear canals, the standardized method for measurement of complex impedances used for the measurement of the audiometric earphone impedances is applied. It is based on the transfer function between two microphone...... locations in an impedance tube. The end of the tube representing the measurement plane is placed at the ear canal entrance. Thus, the impedance seen from the entrance inward is measured on 25 subjects. Most subjects participated in the previous measurement of the ratio between the pressures at the open...

Infill Walls Contribution on the Progressive Collapse Resistance of a Typical Mid-rise RC Framed Building

Science.gov (United States)

Besoiu, Teodora; Popa, Anca

2017-10-01

This study investigates the effect of the autoclaved aerated concrete infill walls on the progressive collapse resistance of a typical RC framed structure. The 13-storey building located in Brăila (a zone with high seismic risk in Romania) was designed according to the former Romanian seismic code P13-70 (1970). Two models of the structure are generated in the Extreme Loading® for Structures computer software: a model with infill walls and a model without infill walls. Following GSA (2003) Guidelines, a nonlinear dynamic procedure is used to determine the progressive collapse risk of the building when a first-storey corner column is suddenly removed. It was found that, the structure is not expected to fail under the standard GSA loading: DL+0.25LL. Moreover, if the infill walls are introduced in the model, the maximum vertical displacement of the node above the removed column is reduced by about 48%.

A potpourri of impedance measurements at the advanced photon source storage ring

International Nuclear Information System (INIS)

Sereno, N.S.; Chae, Y.C.; Harkay, K.C.; Lumpkin, A.H.; Milton, S.V.; Yang, B.X.

1997-01-01

Machine coupling impedances were determined in the APS storage ring from measurements of the bunch length, synchronous phase, and synchrotron and betatron tunes vs single-bunch current. The transverse measurements were performed for various numbers of small gap insertion device (ID) chambers installed in the ring. The transverse impedance is determined from measurements of the transverse tunes and bunch length as a function of single-bunch current. The shift in the synchrotron tune was measured as a function of bunch current from which the total cavity impedance was extracted. The loss factor was determined by measuring the relative synchronous phase as a function of bunch current. The longitudinal resistive impedance is calculated using the loss factor dependence on the bunch length. From these results, the authors can estimate what the impedance would be for a full set of ID chambers

Application of stochastic Galerkin FEM to the complete electrode model of electrical impedance tomography

International Nuclear Information System (INIS)

Leinonen, Matti; Hakula, Harri; Hyvönen, Nuutti

2014-01-01

The aim of electrical impedance tomography is to determine the internal conductivity distribution of some physical body from boundary measurements of current and voltage. The most accurate forward model for impedance tomography is the complete electrode model, which consists of the conductivity equation coupled with boundary conditions that take into account the electrode shapes and the contact resistances at the corresponding interfaces. If the reconstruction task of impedance tomography is recast as a Bayesian inference problem, it is essential to be able to solve the complete electrode model forward problem with the conductivity and the contact resistances treated as a random field and random variables, respectively. In this work, we apply a stochastic Galerkin finite element method to the ensuing elliptic stochastic boundary value problem and compare the results with Monte Carlo simulations

Performance of Multi Walled Carbon Nanotubes Grown on Conductive Substrates as Supercapacitors Electrodes using Organic and Ionic liquid electrolytes

Science.gov (United States)

Winchester, Andrew; Ghosh, Sujoy; Turner, Ben; Zhang, X. F.; Talapatra, Saikat

2012-02-01

In this work we will present the use of Multi Walled Carbon Nanotubes (MWNT) directly grown on inconel substrates via chemical vapor deposition, as electrode materials for electrochemical double layer capacitors (EDLC). The performance of the MWNT EDLC electrodes were investigated using two electrolytes, an organic electrolyte, tetraethylammonium tetrafluoroborate in propylene carbonate (Et4NBF4 in PC), and a room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). Cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy measurements to obtain values for the capacitance and internal resistance of these devices will be presented and compared.

[Cellular composition of lymphoid nodules in the trachea wall in rats with different resistance to emotional stress in a model of hemorrhagic stroke].

Science.gov (United States)

Klyueva, L A

2017-01-01

To reveal regularities of changes in cellular composition of lymphoid nodules in the tracheal wall in male Wistar rats resistant and not resistant to emotional stress in a model of hemorrhagic stroke. Lymphoid formations of the tracheal wall (an area near the bifurcation of the organ) were investigated in 98 male Wistar rats using histological methods. Significant changes in the cellular composition of lymphoid nodules were found. The pattern of changes depends on the stress resistance of rats and the period of the experiment. The active cell destruction in lymphoid nodules was noted both in stress resistant and stress susceptible animals. The changes in the structure of lymphoid nodules found in the experimental hemorrhagic stroke suggest a decrease in the local immune resistance, which is most pronounced in rats not resistant to stress, that may contribute to the development of severe inflammatory complications of stroke such as pneumonia.

Discerning apical and basolateral properties of HT-29/B6 and IPEC-J2 cell layers by impedance spectroscopy, mathematical modeling and machine learning.

Directory of Open Access Journals (Sweden)

Thomas Schmid

Full Text Available Quantifying changes in partial resistances of epithelial barriers in vitro is a challenging and time-consuming task in physiology and pathophysiology. Here, we demonstrate that electrical properties of epithelial barriers can be estimated reliably by combining impedance spectroscopy measurements, mathematical modeling and machine learning algorithms. Conventional impedance spectroscopy is often used to estimate epithelial capacitance as well as epithelial and subepithelial resistance. Based on this, the more refined two-path impedance spectroscopy makes it possible to further distinguish transcellular and paracellular resistances. In a next step, transcellular properties may be further divided into their apical and basolateral components. The accuracy of these derived values, however, strongly depends on the accuracy of the initial estimates. To obtain adequate accuracy in estimating subepithelial and epithelial resistance, artificial neural networks were trained to estimate these parameters from model impedance spectra. Spectra that reflect behavior of either HT-29/B6 or IPEC-J2 cells as well as the data scatter intrinsic to the used experimental setup were created computationally. To prove the proposed approach, reliability of the estimations was assessed with both modeled and measured impedance spectra. Transcellular and paracellular resistances obtained by such neural network-enhanced two-path impedance spectroscopy are shown to be sufficiently reliable to derive the underlying apical and basolateral resistances and capacitances. As an exemplary perturbation of pathophysiological importance, the effect of forskolin on the apical resistance of HT-29/B6 cells was quantified.

Fabrication of single walled carbon nanotubes/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) layers under enhanced gravity drying

International Nuclear Information System (INIS)

Rincón, M.E.; Alvarado-Tenorio, G.; Vargas, M.G.; Ramos, E.; Sánchez-Tizapa, M.

2015-01-01

In this contribution, we explore the use of enhanced gravity in order to achieve composite films of single walled carbon nanotubes (SWCNTs)/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) with improved properties. The samples were characterized by atomic force microscopy, scanning electron microscopy, and electrochemical impedance spectroscopy, in order to determine the differences caused by the enhanced gravity. Impedance spectroscopy results show that there is an improvement of the electrical properties of the SWCNT/PEDOT:PSS junction, manifested as lower contact resistance, modified chemical capacitance, and induced p-type doping. A force-induced interpenetration of the polymer into the SWCNT network and the efficient removal of water and PSS are proposed to explain the results. The transparency and electrical properties of these films forecast their application as a buffer layer in organic solar cell heterojunctions, or as hole transporting materials in perovskite-based solar cells. - Highlights: • A technique to fabricate conductive films of SWCNT/PEDOT:PSS is presented. • The technique is based on enhanced gravity drying. • Improved interpenetration of the bilayer SWCNT/PEDOT:PSS system • Enhanced gravity increases the p-type conductivity of the film. • Impedance spectroscopy confirms the improvement on the electrical properties.

Development of carbon steel with superior resistance to wall thinning and fracture for nuclear piping system

International Nuclear Information System (INIS)

Rhee, Chang Kyu; Lee, Min Ku; Park, Jin Ju

2010-07-01

Carbon steel is usually used for piping for secondary coolant system in nuclear power plant because of low cost and good machinability. However, it is generally reported that carbon steel was failed catastrophically because of its low resistance to wall thinning and fracture toughness. Especially, flow accelerated corrosion (FAC) is one of main problems of the wall thinning of piping in the nuclear power plant. Therefore, in this project, fabrication technology of new advanced carbon steel materials modified by dispersion of nano-carbide ceramics into the matrix is developed first in order to improve the resistance to wall thinning and fracture toughness drastically compared to the conventional one. In order to get highly wettable fine TiC ceramic particles into molten metal, the micro-sized TiC particles were first mechanically milled by Fe (MMed TiC/Fe) in a high energy ball mill machine in Ar gas atmosphere, and then mixed with surfactant metal elements (Sn, Cr, Ni) to obtain better wettability, as this lowered surface tension of the carbon steel melt. According to microscopic images revealed that an addition of MMed TiC/Fe-surfactant mixed powders favorably disperses the fine TiC particles in the carbon steel matrix. It was also found that the grain size refinement of the cast matrix is achieved remarkably when fine TiC particles were added due to the fact that they act as nucleation sites during the solidification process. As a results, a cast carbon steel dispersed with fine TiC particles shows improved mechanical properties such as hardness, tensile strength and cavitation resistance compared to that of without particles. However, the slight decrease of toughness was found

Bench measurement of vacuum chamber impedances with wires

International Nuclear Information System (INIS)

Shafer, R.E.

1979-01-01

Particle beams travelling in an accelerator or storage ring vacuum chamber produce electric and magnetic fields which interact with the walls of the chamber. The induced wall currents in turn generate secondary fields which can interact with the beam, giving rise to both energy loss and other effects which can cause beam instability. In many simple geometries these effects can be calculated. In more complex geometries the calculations are difficult and very approximate. For this reason it is important that the effects be measured if possible prior to installation. As accelerators become larger and the number of vacuum chamber components more numerous, and as more severe beam intensity and stability requirements are placing lower limits on the longitudinal and transverse impedances, a less than adequate component will be more likely to limit machine performance

Heat Conductivity Resistance of Concrete Wall Panel by Water Flowing in Different Orientations of Internal PVC pipe

Science.gov (United States)

Umi, N. N.; Norazman, M. N.; Daud, N. M.; Yusof, M. A.; Yahya, M. A.; Othman, M.

2018-04-01

Green building technology and sustainability development is current focus in the world nowadays. In Malaysia and most tropical countries the maximum temperature recorded typically at 35°C. Air-conditioning system has become a necessity in occupied buildings, thereby increasing the cost of electric consumption. The aim of this study is to find out the solution in minimizing heat transfer from the external environment and intentions towards going green. In this study, the experimental work includes testing three types of concrete wall panels. The main heat intervention material in this research is 2 inch diameter Polyvinyl Chloride (PVC) pipe embedded at the center of the concrete wall panel, while the EPS foam beads were added to the cement content in the concrete mix forming the outer layer of the wall panel. Water from the rainwater harvesting system is regulated in the PVC pipe to intervene with the heat conductivity through the wall panel. Results from the experimental works show that the internal surface temperature of these heat resistance wall panels is to 3□C lower than control wall panel from plain interlocking bricks.

Lateral resistance of plybamboo wall-panels

OpenAIRE

Gonzalez Beltran, G.E.; Herwijnen, van, F.; Janssen, J.J.A.; Moonen, S.P.G.; Gutierrez, J.A.

2003-01-01

This paper deals with the experimental and theoretical behavior of plybamboo (kind of plywood made out of bamboo) wall-panels subjected to lateral load. The wall-panels are part of a house design method proposed in the author's PhD thesis for prefabricated social housing in developing countries. Sixteen fullscaled wallpanels with or without window and door openings were tested and their theoretical capacities estimated. Design wind and seismic loads were determined according to the Internatio...

Characterization of high impedance connecting links for Bolometric detectors

Energy Technology Data Exchange (ETDEWEB)

Giachero, A. [INFN, Sezione di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Università di Milano Bicocca, Dipartimento di Fisica G. Occhialini, Piazza della Scienza 3, I-20126 Milano (Italy); Gotti, C. [INFN, Sezione di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Università di Milano Bicocca, Dipartimento di Fisica G. Occhialini, Piazza della Scienza 3, I-20126 Milano (Italy); Università di Firenze, Dipartimento di Elettronica e Telecomunicazioni, Via S. Marta 3, I-50139 Firenze (Italy); Maino, M. [INFN, Sezione di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Università di Milano Bicocca, Dipartimento di Fisica G. Occhialini, Piazza della Scienza 3, I-20126 Milano (Italy); Pessina, G., E-mail: pessina@mib.infn.it [INFN, Sezione di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Università di Milano Bicocca, Dipartimento di Fisica G. Occhialini, Piazza della Scienza 3, I-20126 Milano (Italy)

2013-08-01

High impedance connecting links and cables are tested at low frequency in terms of their parasitic impedance to ground and to neighboring connecting links. These parameters must be well characterized with detectors operated at low temperature, especially when the very front-end is at room temperature, which results in a long link. This is the case of the LUCIFER experiment, an array of crystals where every event of interest produces two signals, one composed of phonons, the other of photons. The parasitic impedance is usually considered to be the parallel combination of a resistance and a capacitance. We characterized both and found that from the static measurements the capacitance of the cable resulted much larger. On the basis of this result we optimized the measurement set-up and developed a model to account for this behavior.

Application of impedance spectroscopy to SOFC research

Energy Technology Data Exchange (ETDEWEB)

Hsieh, G.; Mason, T.O. [Northwestern Univ., Evanston, IL (United States); Pederson, L.R. [Pacific Northwest National Lab., Richland, WA (United States)

1996-12-31

With the resurgence of interest in solid oxide fuel cells and other solid state electrochemical devices, techniques originally developed for characterizing aqueous systems are being adapted and applied to solid state systems. One of these techniques, three-electrode impedance spectroscopy, is particularly powerful as it allows characterization of subcomponent and interfacial properties. Obtaining accurate impedance spectra, however, is difficult as reference electrode impedance is usually non-negligible and solid electrolytes typically have much lower conductance than aqueous solutions. Faidi et al and Chechirlian et al have both identified problems associated with low conductivity media. Other sources of error are still being uncovered. Ford et al identified resistive contacts with large time constants as a possibility, while Me et al showed that the small contact capacitance of the reference electrode was at fault. Still others show that instrument limitations play a role. Using the voltage divider concept, a simplified model that demonstrates the interplay of these various factors, predicts the form of possible distortions, and offers means to minimize errors is presented.

Investigating the low-temperature impedance increase of lithium-ion cells

International Nuclear Information System (INIS)

Abraham, D. P.; Heaton, J. R.; Kang, S.-H.; Dees, D. W.; Jansen, A. N.; Chemical Engineering

2008-01-01

Low-temperature performance loss is a significant barrier to commercialization of lithium-ion cells in hybrid electric vehicles. Increased impedance, especially at temperatures below 0 C, reduces the cell pulse power performance required for cold engine starts, quick acceleration, or regenerative braking. Here we detail electrochemical impedance spectroscopy data on binder- and carbon-free layered-oxide and spinel-oxide electrodes, obtained over the +30 to ?30 C temperature range, in coin cells containing a lithium-preloaded Li 4/3 Ti 5/3 O 4 composite (LTOc) counter electrode and a LiPF 6 -bearing ethylene carbonate/ethyl methyl carbonate electrolyte. For all electrodes studied, the impedance increased with decreasing cell temperature; the increases observed in the midfrequency arc dwarfed the increases in ohmic resistance and diffusional impedance. Our data suggest that the movement of lithium ions across the electrochemical interface on the active material may have been increasingly hindered at lower temperatures, especially below 0 C. Low-temperature performance may be improved by modifying the electrolyte-active material interface (for example, through electrolyte composition changes). Increasing surface area of active particles (for example, through nanoparticle use) can lower the initial electrode impedance and lead to lower cell impedances at -30 C

Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics

Directory of Open Access Journals (Sweden)

Tushar Kanti Bera

2014-06-01

Full Text Available When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS. We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor.

An electrochemical impedance spectroscopy study of polymer electrolyte membrane fuel cells electrocatalyst single wall carbon nanohorns-supported.

Science.gov (United States)

Brandão, Lúcia; Boaventura, Marta; Passeira, Carolina; Gattia, Daniele Mirabile; Marazzi, Renzo; Antisari, Marco Vittori; Mendes, Adélio

2011-10-01

Electrochemical impedance spectroscopy (EIS) was used to study the polymer electrolyte membrane fuel cells (PEMFC) performance when using single wall carbon nanohorns (SWNH) to support Pt nanoparticles. Additionally, as-prepared and oxidized SWNH Pt-supports were compared with conventional carbon black. Two different oxidizing treatments were considered: oxygen flow at 500 degrees C and reflux in an acid solution at 85 degrees C. Both oxidizing treatments increased SWNH surface area; oxygen treatment increased surface area 4 times while acid treatment increased 2.6 times. The increase in surface area should be related to the opening access to the inner tube of SWNH. Acid treatment of SWNH increased chemical fragility and decreased electrocatalyst load in comparison with as-prepared SWNH. On the other hand, the oxygen treated SWNH sample allowed to obtain the highest electrocatalyst load. The use of as-prepared and oxygen treated SWNH showed in both cases catalytic activities 60% higher than using conventional carbon black as electrocatalyst support in PEMFC. Moreover, EIS analysis indicated that the major improvement in performance is related to the cathode kinetics in the as-prepared SWNH sample, while concerning the oxidized SWNH sample, the improvements are related to the electrokinetics in both anode and cathode electrodes. These improvements should be related with differences in the hydrophobic character between SWNH and carbon black.

A study of passivation/depassivation of carbon steel; electrochemical impedance spectrocopy vs. potential noise fluctuations

International Nuclear Information System (INIS)

Roberge, P.R.; Halliop, E.; Sastri, V.S.

1992-01-01

A technique based on recording corrosion potential fluctuations generated by corroding electrodes was used under open-circuit conditions to study passivation and depassivation of carbon steel. Quantification of the electrochemical signal in terms of the pitting corrosion rate has been attempted. The amplitude of electrochemical noise signals was analyzed under different pitting conditions and correlated to polarization resistance values obtained from the electrochemical impedance spectra. The automatic statistical data analysis of electrochemical impedance data points has been successfully applied to calculate polarization resistance values and other interesting characteristics of such measurements

Freezing resistance in Patagonian woody shrubs: the role of cell wall elasticity and stem vessel size.

Science.gov (United States)

Zhang, Yong-Jiang; Bucci, Sandra J; Arias, Nadia S; Scholz, Fabian G; Hao, Guang-You; Cao, Kun-Fang; Goldstein, Guillermo

2016-08-01

Freezing resistance through avoidance or tolerance of extracellular ice nucleation is important for plant survival in habitats with frequent subzero temperatures. However, the role of cell walls in leaf freezing resistance and the coordination between leaf and stem physiological processes under subzero temperatures are not well understood. We studied leaf and stem responses to freezing temperatures, leaf and stem supercooling, leaf bulk elastic modulus and stem xylem vessel size of six Patagonian shrub species from two sites (plateau and low elevation sites) with different elevation and minimum temperatures. Ice seeding was initiated in the stem and quickly spread to leaves, but two species from the plateau site had barriers against rapid spread of ice. Shrubs with xylem vessels smaller in diameter had greater stem supercooling capacity, i.e., ice nucleated at lower subzero temperatures. Only one species with the lowest ice nucleation temperature among all species studied exhibited freezing avoidance by substantial supercooling, while the rest were able to tolerate extracellular freezing from -11.3 to -20 °C. Leaves of species with more rigid cell walls (higher bulk elastic modulus) could survive freezing to lower subzero temperatures, suggesting that rigid cell walls potentially reduce the degree of physical injury to cell membranes during the extracellular freezing and/or thaw processes. In conclusion, our results reveal the temporal-spatial ice spreading pattern (from stem to leaves) in Patagonian shrubs, and indicate the role of xylem vessel size in determining supercooling capacity and the role of cell wall elasticity in determining leaf tolerance of extracellular ice formation. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Smart Multi-Frequency Bioelectrical Impedance Spectrometer for BIA and BIVA Applications.

Science.gov (United States)

Harder, Rene; Diedrich, Andre; Whitfield, Jonathan S; Buchowski, Macie S; Pietsch, John B; Baudenbacher, Franz J

2016-08-01

Bioelectrical impedance analysis (BIA) is a noninvasive and commonly used method for the assessment of body composition including body water. We designed a small, portable and wireless multi-frequency impedance spectrometer based on the 12 bit impedance network analyzer AD5933 and a precision wide-band constant current source for tetrapolar whole body impedance measurements. The impedance spectrometer communicates via Bluetooth with mobile devices (smart phone or tablet computer) that provide user interface for patient management and data visualization. The export of patient measurement results into a clinical research database facilitates the aggregation of bioelectrical impedance analysis and biolectrical impedance vector analysis (BIVA) data across multiple subjects and/or studies. The performance of the spectrometer was evaluated using a passive tissue equivalent circuit model as well as a comparison of body composition changes assessed with bioelectrical impedance and dual-energy X-ray absorptiometry (DXA) in healthy volunteers. Our results show an absolute error of 1% for resistance and 5% for reactance measurements in the frequency range of 3 kHz to 150 kHz. A linear regression of BIA and DXA fat mass estimations showed a strong correlation (r(2)=0.985) between measures with a maximum absolute error of 6.5%. The simplicity of BIA measurements, a cost effective design and the simple visual representation of impedance data enables patients to compare and determine body composition during the time course of a specific treatment plan in a clinical or home environment.

Assessing the immediate impact of botulinum toxin injection on impedance of spastic muscle.

Science.gov (United States)

Li, Xiaoyan; Shin, Henry; Li, Le; Magat, Elaine; Li, Sheng; Zhou, Ping

2017-05-01

This study aimed to investigate the immediate impacts of Botulinum Toxin A (BoNT-A) injections on the inherent electrical properties of spastic muscles using a newly developed electrical impedance myography (EIM) technique. Impedance measures were performed before and after a BoNT-A injection in biceps brachii muscles of 14 subjects with spasticity. Three major impedance variables, resistance (R), reactance (X) and phase angle (θ) were obtained from three different configurations, and were evaluated using the conventional EIM frequency at 50kHz as well as multiple frequency analysis. Statistical analysis demonstrated a significant decrease of resistance in the injected muscles (Multiple-frequency: R pre =25.17±1.94Ohm, R post =23.65±1.63Ohm, ptoxin effects on the muscle. This study demonstrated high sensitivity of the EIM technique in the detection of alterations to muscle composition. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Bacillus subtilis as a Platform for Molecular Characterisation of Regulatory Mechanisms of Enterococcus faecalis Resistance against Cell Wall Antibiotics

OpenAIRE

Fang, Chong; Stiegeler, Emanuel; Cook, Gregory M.; Mascher, Thorsten; Gebhard, Susanne

2014-01-01

To combat antibiotic resistance of Enterococcus faecalis, a better understanding of the molecular mechanisms, particularly of antibiotic detection, signal transduction and gene regulation is needed. Because molecular studies in this bacterium can be challenging, we aimed at exploiting the genetically highly tractable Gram-positive model organism Bacillus subtilis as a heterologous host. Two fundamentally different regulators of E. faecalis resistance against cell wall antibiotics, the bacitra...

Lung and chest wall impedances in the dog in normal range of breathing: effects of pulmonary edema.

Science.gov (United States)

Barnas, G M; Stamenović, D; Lutchen, K R

1992-09-01

We evaluated the effect of pulmonary edema on the frequency (f) and tidal volume (VT) dependences of respiratory system mechanical properties in the normal ranges of breathing. We measured resistance and elastance of the lungs (RL and EL) and chest wall of four anesthetized-paralyzed dogs during sinusoidal volume oscillations at the trachea (50-300 ml, 0.2-2 Hz), delivered at a constant mean airway pressure. Measurements were made before and after severe pulmonary edema was produced by injection of 0.06 ml/kg oleic acid into the right atrium. Chest wall properties were not changed by the injection. Before oleic acid, EL increased slightly with increasing f in each dog but was independent of VT. RL decreased slightly and was independent of VT from 0.2 to 0.4 Hz, but above 0.4 Hz it tended to increase with increasing flow, presumably due to the airway contribution. After oleic acid injection, EL and RL increased greatly. Large negative dependences of EL on VT and of RL on f were also evident, so that EL and RL after oleic acid changed two- and fivefold, respectively, within the ranges of f and VT studied. We conclude that severe pulmonary edema changes lung properties so as to make behavior VT dependent (i.e., nonlinear) and very frequency dependent in the normal range of breathing.

Techniques for beam impedance measurements above cutoff

International Nuclear Information System (INIS)

Lambertson, G.R.; Jacob, A.F.; Rimmer, R.A.; Voelker, F.

1990-08-01

Methods for measuring beam impedance above cutoff have been very limited. For design work on the ALS we have developed two techniques that yield data in the frequency domain with high sensitivity. The first is an extension of the wire method; the second utilizes traveling TM waves to simulate the beam's fields at the wall, and thus avoids the mechanical difficulties of mounting the wire. It is also more sensitive than the other method but the interpretation is complicated by the presence of higher order modes. With either method we were able to detect resonant peaks smaller than 1 Ohm at 10 GHz

Evaluation of Bioelectrical Impedance Spectroscopy for the Assessment of Extracellular Body Water

Directory of Open Access Journals (Sweden)

Sören Weyer

2012-01-01

Full Text Available This study evaluates bioelectrical impedance spectroscopy (BIS measurements to detect body fluid status. The multifrequency impedance measurements were performed in five female pigs. Animals were connected to an extracorporeal membrane oxygenation device during a lung disease experiment and fluid balance was recorded. Every 15 min the amount of fluid infusion and the weight of the urine drainage bag was recorded. From the fluid intake and output, the fluid balance was calculated. These data were compared with values calculated from a mathematical model, based on the extracellular tissue resistance and the Hanai Mixture theory. The extracellular tissue resistance was also measured with BIS. These experimental results strongly support the feasibility and clinical value of BIS for in vivo assessment of the hydration status.

\\mathscr{H}_2 optimal control techniques for resistive wall mode feedback in tokamaks

Science.gov (United States)

Clement, Mitchell; Hanson, Jeremy; Bialek, Jim; Navratil, Gerald

2018-04-01

DIII-D experiments show that a new, advanced algorithm enables resistive wall mode (RWM) stability control in high performance discharges using external coils. DIII-D can excite strong, locked or nearly locked external kink modes whose rotation frequencies and growth rates are on the order of the magnetic flux diffusion time of the vacuum vessel wall. Experiments have shown that modern control techniques like linear quadratic Gaussian (LQG) control require less current than the proportional controller in use at DIII-D when using control coils external to DIII-D’s vacuum vessel. Experiments were conducted to develop control of a rotating n  =  1 perturbation using an LQG controller derived from VALEN and external coils. Feedback using this LQG algorithm outperformed a proportional gain only controller in these perturbation experiments over a range of frequencies. Results from high βN experiments also show that advanced feedback techniques using external control coils may be as effective as internal control coil feedback using classical control techniques.

Application of non-destructive impedance-based monitoring technique for cyclic fatigue evaluation of endodontic nickel-titanium rotary instruments.

Science.gov (United States)

Chang, Yau-Zen; Liu, Mou-Chuan; Pai, Che-An; Lin, Chun-Li; Yen, Kuang-I

2011-06-01

This study investigates the application of non-destructive testing based on the impedance theory in the cyclic fatigue evaluation of endodontic Ni-Ti rotary instruments. Fifty Ni-Ti ProTaper instruments were divided into five groups (n=10 in Groups A to E). Groups A to D were subjected to cyclic fatigue within an artificial canal (Group E was the control group). The mean value of the total life limit (TLL), defined as the instrument being rotated until fracture occurred was found to be 104 s in Group A. Each rotary instrument in Groups B, C and D were rotated until the tested instruments reached 80% (84 s), 60% (62 s) and 40% (42 s) of the TLL. After fatigue testing, each rotary instrument was mounted onto a custom-developed non-destructive testing device to give the tip of the instrument a progressive sideways bend in four mutually perpendicular directions to measure the corresponding impedance value (including the resistance and the reactance). The results indicated that the impedance value showed the same trend as the resistance, implying that the impedance was primarily affected by the resistance. The impedance value for the instruments in the 80% and 60% TLL groups increased by about 6 mΩ (about 7.5%) more than that of the instruments in the intact and 40% TLL groups. The SEM analysis result showed that crack striations were only found at the tip of the thread on the cracked surface of the instrument, consistent with the impedance measurements that found the impedance value of the cracked surface to be significantly different from those in other surfaces. These findings indicate that the impedance value may represent an effective parameter for evaluating the micro-structural status of Ni-Ti rotary instruments subjected to fatigue loading. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Theory of fractional order elements based impedance matching networks

KAUST Repository

Radwan, Ahmed G.

2011-03-01

Fractional order circuit elements (inductors and capacitors) based impedance matching networks are introduced for the first time. In comparison to the conventional integer based L-type matching networks, fractional matching networks are much simpler and versatile. Any complex load can be matched utilizing a single series fractional element, which generally requires two elements for matching in the conventional approach. It is shown that all the Smith chart circles (resistance and reactance) are actually pairs of completely identical circles. They appear to be single for the conventional integer order case, where the identical circles completely overlap each other. The concept is supported by design equations and impedance matching examples. © 2010 IEEE.

Effect of the resistive wall on the growth rate of weakly unstable external kink mode in general 3D configurations

International Nuclear Information System (INIS)

Chu, M.S.; Ichiguchi, K.

2005-05-01

Formation of a method for the systematic computation of the growth rate of the weakly unstable RWM in 3D configurations by using results from ideal stability codes is presented. It is shown that the growth rate of the RWM is approximately given by the rate at which the available free energy for the ideal external kink mode can be dissipated by the resistive wall. The eigenfunction is also approximated by that of the external kink mode. This formulation is demonstrated by coupling to the ideal MHD code KSTEP with computation of the dissipation on the resistive wall. Results of the stability of the RWM in LHD plasmas and discussion on the validity and improvement to the computation are also included. (author)

Current distribution effects in AC impedance spectroscopy of electroceramic point contact and thin film model electrodes

DEFF Research Database (Denmark)

Nielsen, Jimmi; Jacobsen, Torben

2010-01-01

the primary current distribution to the DC current distribution restricted to the Three-Phase-Boundary (TPB) zone introduces an error in the determination of the reaction resistance, Rreac = Z(freq. → 0) − Z(freq. → ∞). The error is estimated for different width of the effective TPB zone and a rule of thumb...... regarding its significance is provided. The associated characteristic impedance spectrum shape change is simulated and its origin discussed. Furthermore, the characteristic shape of impedance spectra of thin electroceramic film electrodes with lateral ohmic resistance is studied as a function...

Impedance spectroscopy study of Na{sub 1/2}Sm{sub 1/2}TiO{sub 3} ceramic

Energy Technology Data Exchange (ETDEWEB)

Barik, S K; Choudhary, R N.P. [I.I.T., Department of Physics and Meteorology, Kharagpur (India); Mahapatra, P K [Vidyasagar University, Department of Physics and Technophysics, Midnapur, West Bengal (India)

2007-07-15

Complex impedance analysis of a valence-compensated perovskite ceramic oxide Na{sub 1/2}Sm{sub 1/2}TiO{sub 3}, prepared by a mixed oxide (solid-state reaction) method, has been carried out. The formation of single-phase material was confirmed by X-ray diffraction studies, and it was found to be an orthorhombic phase at room temperature. In a scanning electron microscope, grains separated by well-defined boundaries are visible, which is in good agreement with that of impedance analysis. Alternating current impedance measurements were made over a wide temperature range (31-400 C) in an air atmosphere. Complex impedance and modulus plots helped to separate out the contributions of grain and grain boundaries to the overall polarization or electrical behavior. The physical structure of the samples was visualized most prominently at higher temperatures (275 C) from the Nyquist plots showing inter- and intragranular impedance present in the material. The frequency dependence of electrical data is also analyzed in the framework of the conductivity and modulus formalisms. The bulk resistance, evaluated from the impedance spectrum, was observed to decrease with rise in temperature, showing a typical negative temperature coefficient of resistance-type behavior like that of semiconductors. The modulus mechanism indicates the non-Debye type of conductivity relaxation in the materials, which is supported by the impedance data. (orig.)

Physical and Chemical Barriers in Root Tissues Contribute to Quantitative Resistance to Fusarium oxysporum f. sp. pisi in Pea

Directory of Open Access Journals (Sweden)

Moustafa Bani

2018-02-01

Full Text Available Fusarium wilt caused by Fusarium oxysporum f. sp. pisi (Fop is one of the most destructive diseases of pea worldwide. Control of this disease is difficult and it is mainly based on the use of resistant cultivars. While monogenic resistance has been successfully used in the field, it is at risk of breakdown by the constant evolution of the pathogen. New sources of quantitative resistance have been recently identified from a wild relative Pisum spp. collection. Here, we characterize histologically the resistance mechanisms occurring in these sources of quantitative resistance. Detailed comparison, of the reaction at cellular level, of eight pea accessions with differential responses to Fop race 2, showed that resistant accessions established several barriers at the epidermis, exodermis, cortex, endodermis and vascular stele efficiently impeding fungal progression. The main components of these different barriers were carbohydrates and phenolic compounds including lignin. We found that these barriers were mainly based on three defense mechanisms including cell wall strengthening, formation of papilla-like structures at penetration sites and accumulation of different substances within and between cells. These defense reactions varied in intensity and localization between resistant accessions. Our results also clarify some steps of the infection process of F. oxysporum in plant and support the important role of cell wall-degrading enzymes in F. oxysporum pathogenicity.

Using Piezoelectric Devices to Transmit Power through Walls

Science.gov (United States)

Sherrit, Stewart; Bar-Cohen, Yoseph; Bao, Xiaoqi

2008-01-01

A method denoted wireless acoustic-electric feed-through (WAEF) has been conceived for transmitting power and/or data signals through walls or other solid objects made of a variety of elastic materials that could be electrically conductive or nonconductive. WAEF would make it unnecessary to use wires, optical fibers, tubes, or other discrete wall-penetrating signal-transmitting components, thereby eliminating the potential for structural weakening or leakage at such penetrations. Avoidance of such penetrations could be essential in some applications in which maintenance of pressure, vacuum, or chemical or biological isolation is required. In a basic WAEF setup, a transmitting piezoelectric transducer on one side of a wall would be driven at resonance to excite ultrasonic vibrations in the wall. A receiving piezoelectric transducer on the opposite side of the wall would convert the vibrations back to an ultrasonic AC electric signal, which would then be detected and otherwise processed in a manner that would depend on the modulation (if any) applied to the signal and whether the signal was used to transmit power, data, or both. An electromechanical-network model has been derived as a computationally efficient means of analyzing and designing a WAEF system. This model is a variant of a prior model, known in the piezoelectric-transducer art as Mason's equivalent-circuit model, in which the electrical and mechanical dynamics, including electromechanical couplings, are expressed as electrical circuit elements that can include inductors, capacitors, and lumped-parameter complex impedances. The real parts of the complex impedances are used to account for dielectric, mechanical, and coupling losses in all components (including all piezoelectric-transducer, wall, and intermediate material layers). In an application to a three-layer piezoelectric structure, this model was shown to yield the same results as do solutions of the wave equations of piezoelectricity and acoustic

Study of the dopamine effect into cell solutions by impedance analysis

Science.gov (United States)

Paivana, G.; Apostolou, T.; Kaltsas, G.; Kintzios, S.

2017-11-01

Electrochemical Impedance Spectroscopy (EIS) has become a technique that is frequently used for biological assays. Impedance is defined as a complex - valued generalization of resistance and varies depending on its use per application field. In health sciences, bioimpedance is widely used as non-invasive and low cost alternative in many medical areas that provides valuable information about health status. This work focuses on assessing the effects of a bioactive substance applied to immobilized cells. Dopamine was used as a stimulant in order to implement impedance analysis with a specific type of cells. Dopamine constitutes one of the most important catecholamine neurotransmitters in both the mammalian central and peripheral nervous systems. The main purpose is to extract calibration curves at different frequencies with known dopamine concentrations in order to describe the behavior of cells applied to dopamine using an impedance measurement device. For comparison purposes, non-immobilized cells were tested for the same dopamine concentrations.

Impedances of nickel electrodes cycled in various KOH concentrations

Science.gov (United States)

Reid, Margaret A.; Loyselle, Patricia L.

1991-01-01

Recent tests at Hughes have shown that Ni/H2 cells cycled in 26 percent KOH have much longer lives than those cycled in other concentrations. As part of an ongoing program to try to correlate the impedances of nickel electrodes with their life and performance, impedances were measured of a number of electrodes from these tests that had been cycled in concentrations from 21 to 36 percent KOH. These had ranged from about 1000 to 40,000 cycles. After cycling ten times to reduce possible changes due to storage, impedances were measured at five voltages corresponding to low states of charge. The results were analyzed using a standard circuit model including Warburg impedance term. Lower kinetic resistances and Warburg slopes were found for several electrodes which had been cycled in 26 percent KOH even though they had been cycled for a much longer time than the others. Interpretation of the data is complicated by the fact that the cycle lives, storage times, and failure mechanisms varied. Several other circuit models have also been examined, but the best correlations with life were found with parameters obtained from the simple model.

Selective Harmonic Virtual Impedance for Voltage Source Inverters with LCL filter in Microgrids

DEFF Research Database (Denmark)

Savaghebi, Mehdi; Vasquez, Juan Carlos; Jalilian, Alireza Jalilian

2012-01-01

This paper presents a new control approach for voltage source inverters ended with LCL filters for microgrid applications. The control approach consists of voltage and current inner control loops in order to fix the filter capacitor voltage and a virtual impedance loop. The virtual impedance...... is added in order to mitigate the voltage distortion after the output inductor and improve the load sharing among parallel inverters. A general case with a combined voltage harmonic and unbalance distortion is considered. In such a case, voltage distortion is mitigated by inserting capacitive virtual...... impedance for negative sequence of fundamental component as well as positive and negative sequences of main harmonic components. Furthermore, resistive virtual impedances are added at these components in order to provide a proper load sharing and make the overall system more damped. Simulation results...

Converting Sabine absorption coefficients to random incidence absorption coefficients

DEFF Research Database (Denmark)

Jeong, Cheol-Ho

2013-01-01

are suggested: An optimization method for the surface impedances for locally reacting absorbers, the flow resistivity for extendedly reacting absorbers, and the flow resistance for fabrics. With four porous type absorbers, the conversion methods are validated. For absorbers backed by a rigid wall, the surface...... coefficients to random incidence absorption coefficients are proposed. The overestimations of the Sabine absorption coefficient are investigated theoretically based on Miki's model for porous absorbers backed by a rigid wall or an air cavity, resulting in conversion factors. Additionally, three optimizations...... impedance optimization produces the best results, while the flow resistivity optimization also yields reasonable results. The flow resistivity and flow resistance optimization for extendedly reacting absorbers are also found to be successful. However, the theoretical conversion factors based on Miki's model...

Spheromak Impedance and Current Amplification

International Nuclear Information System (INIS)

Fowler, T K; Hua, D D; Stallard, B W

2002-01-01

It is shown that high current amplification can be achieved only by injecting helicity on the timescale for reconnection, τ REC , which determines the effective impedance of the spheromak. An approximate equation for current amplification is: dI TOR 2 /dt ∼ I 2 /τ REC - I TOR 2 /τ closed where I is the gun current, I TOR is the spheromak toroidal current and τ CLOSED is the ohmic decay time of the spheromak. Achieving high current amplification, I TOR >> I, requires τ REC CLOSED . For resistive reconnection, this requires reconnection in a cold zone feeding helicity into a hot zone. Here we propose an impedance model based on these ideas in a form that can be implemented in the Corsica-based helicity transport code. The most important feature of the model is the possibility that τ REC actually increases as the spheromak temperature increases, perhaps accounting for the ''voltage sag'' observed in some experiments, and a tendency toward a constant ratio of field to current, B ∝ I, or I TOR ∼ I. Program implications are discussed

Mechanically Reconfigurable Microstrip Lines Loaded with Stepped Impedance Resonators and Potential Applications

Directory of Open Access Journals (Sweden)

J. Naqui

2014-01-01

Full Text Available This paper is focused on exploring the possibilities and potential applications of microstrip transmission lines loaded with stepped impedance resonators (SIRs etched on top of the signal strip, in a separated substrate. It is shown that if the symmetry plane of the line (a magnetic wall is perfectly aligned with the electric wall of the SIR at the fundamental resonance, the line is transparent. However, if symmetry is somehow ruptured, a notch in the transmission coefficient appears. The notch frequency and depth can thus be mechanically controlled, and this property can be of interest for the implementation of sensors and barcodes, as it is discussed.

Electrochemical impedance spectroscopy of dodecylsulphate doped polypyrrole films in the dark and under illumination

Directory of Open Access Journals (Sweden)

Martini Milena

2000-01-01

Full Text Available The morphology, thickness, oxidation and illumination effects in dodecylsulphate doped polypyrrole films can be qualitatively observed by EIS and consist in variations of interfacial and bulk resistances and capacitances of a proposed equivalent circuit. The circuit well with the measured spectra of films obtained with 190 mC cm-2 of synthesis charge density. For thinner films the calculated values observed by electrochemical impedance spectroscopy (EIS deviate probably due to the absence of diffusion effects. The oxidation of the films diminishes the total impedance over the entire frequency range. The morphology effects are also observed in the entire spectra. The illumination effects are reversible and are observed as expected only in the reduced form of the polymer. The illumination reduces the internal resistance and the space-charge capacitance and increases the charge transfer resistance and the double layer capacitance.

Electrical impedance tomography: topology optimization

International Nuclear Information System (INIS)

Miranda, Lenine Campos

2013-01-01

The Electrical Impedance Tomography (EIT) is a study of body parts who use electric current. Is studied through computers resistance or conductivity of these parts, producing an image used for medical diagnosis. A body is wrapped in a blanket placed with small electrodes and receivers of electric current, potential difference. Based on data obtained from a series of measurements at the electrodes, one by one, sending and receiving, you can perform a numerical phantom, where each 'voxel' of the image formed computationally represents the impedance of biological tissue. In Brazil, studies on electrical impedance tomography (EIT) has not yet started. Such equipment are measured tensions - potential difference - between each electrode / sensor one by one, as a way to Simple Combinatorial Analysis. The sequence and the way it is measured strains are in the final image quality. Finite Element Method Interactive, whose algorithm is based on Dialectical Method. We use an initial function with the objective of maximizing the data quantitatively, for better qualitative analysis. Topology Optimization methods are used to improve the image reconstruction. Currently the study is quite primitive related to the theory that shows how to power the new science studied. The high quality images requires a difficulty in obtaining. This work is not intended for detailed for analysis in any tissue or organ specific, but in general terms. And the formation of the 2D image. 3D need a reconstructor to part. (author)

Tunable nanogap devices for ultra-sensitive electrochemical impedance biosensing

Energy Technology Data Exchange (ETDEWEB)

Lu, Yong [Department of Chemistry, Wannan Medical College, Wuhu 241002 (China); Guo, Zheng [Nanomaterials and Environmental Detection Laboratory, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031 (China); Song, Jing-Jing; Huang, Qin-An; Zhu, Si-Wei [Department of Chemistry, Wannan Medical College, Wuhu 241002 (China); Huang, Xing-Jiu [Nanomaterials and Environmental Detection Laboratory, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031 (China); Wei, Yan, E-mail: yanwei_wnmc@hotmail.com [Department of Chemistry, Wannan Medical College, Wuhu 241002 (China)

2016-01-28

A wealth of research has been available discussing nanogap devices for detecting very small quantities of biomolecules by observing their electrical behavior generally performed in dry conditions. We report that a gold nanogapped electrode with tunable gap length for ultra-sensitive detection of streptavidin based on electrochemical impedance technique. The gold nanogap is fabricated using simple monolayer film deposition and in-situ growth of gold nanoparticles in a traditional interdigitated array (IDA) microelectrode. The electrochemical impedance biosensor with a 25-nm nanogap is found to be ultra-sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin hinder the electron transfer between two electrodes, resulting in a large increase in electron-transfer resistance (R{sub et}) for operating the impedance. A linear relation between the relative R{sub et} and the logarithmic value of streptavidin concentration is observed in the concentration range from 1 pM (picomolar) to 100 nM (nanomolar). The lowest detectable concentration actually measured reaches 1 pM. We believe that such an electrochemical impedance nanogap biosensor provides a useful approach towards biomolecular detection that could be extended to a number of other systems. - Highlights: • A tunable gold nanogap device was used as to electrochemical impedance biosensor. • Linear range from 1 pM to 100 nM with LOD of 1 pM for streptavidin detection was obtained. • The nanogap devices exhibit a satisfactory precision, stability, and reproducibility. • The combination of electrochemical impedance technique and nanogap devices was achieved.

Bacillus subtilis as a platform for molecular characterisation of regulatory mechanisms of Enterococcus faecalis resistance against cell wall antibiotics.

Science.gov (United States)

Fang, Chong; Stiegeler, Emanuel; Cook, Gregory M; Mascher, Thorsten; Gebhard, Susanne

2014-01-01

To combat antibiotic resistance of Enterococcus faecalis, a better understanding of the molecular mechanisms, particularly of antibiotic detection, signal transduction and gene regulation is needed. Because molecular studies in this bacterium can be challenging, we aimed at exploiting the genetically highly tractable Gram-positive model organism Bacillus subtilis as a heterologous host. Two fundamentally different regulators of E. faecalis resistance against cell wall antibiotics, the bacitracin sensor BcrR and the vancomycin-sensing two-component system VanSB-VanRB, were produced in B. subtilis and their functions were monitored using target promoters fused to reporter genes (lacZ and luxABCDE). The bacitracin resistance system BcrR-BcrAB of E. faecalis was fully functional in B. subtilis, both regarding regulation of bcrAB expression and resistance mediated by the transporter BcrAB. Removal of intrinsic bacitracin resistance of B. subtilis increased the sensitivity of the system. The lacZ and luxABCDE reporters were found to both offer sensitive detection of promoter induction on solid media, which is useful for screening of large mutant libraries. The VanSB-VanRB system displayed a gradual dose-response behaviour to vancomycin, but only when produced at low levels in the cell. Taken together, our data show that B. subtilis is a well-suited host for the molecular characterization of regulatory systems controlling resistance against cell wall active compounds in E. faecalis. Importantly, B. subtilis facilitates the careful adjustment of expression levels and genetic background required for full functionality of the introduced regulators.

Process modeling of the impedance characteristics of proton exchange membrane fuel cells

International Nuclear Information System (INIS)

Rezaei Niya, Seyed Mohammad; Phillips, Ryan K.; Hoorfar, Mina

2016-01-01

Highlights: • The impedance of the PEM fuel cell is analytically calculated. • The measured impedances are presented for different operating conditions. • The high frequency arc in the measured Nyquist plot is related to the anode. • The intermediate frequency arc is related to the cathode. • The low frequency arc and high frequency resistance are related to the membrane. - Abstract: A complete process modeling of the impedance characteristics of the proton exchange membrane fuel cells is presented. The impedance of the cell is determined analytically and the resultant equivalent circuit is calculated. The model predictions are then compared against the measured impedances in different current densities, operating temperatures and anode and cathode relative humidities. It is shown that the model predicts the Nyquist plots in all different operating conditions extremely well. Next, the trends observed in the Nyquist plots reported in the literature are compared against the model predictions. The result of this comparison confirms the accuracy of the model. Using the verified model, various arcs in the Nyquist plots are separated and related to the fuel cell physical parameters.

Development of AC impedance methods for evaluating corroding metal surfaces and coatings

Science.gov (United States)

Knockemus, Ward

1986-01-01

In an effort to investigate metal surface corrosion and the breakdown of metal protective coatings the AC Impedance Method was applied to zinc chromate primer coated 2219-T87 aluminum. The model 368-1 AC Impedance Measurement System recently acquired by the MSFC Corrosion Research Branch was used to monitor changing properties of coated aluminum disks immersed in 3.5% NaCl buffered at ph 5.5 over three to four weeks. The DC polarization resistance runs were performed on the same samples. The corrosion system can be represented by an electronic analog called an equivalent circuit that consists of transistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for resistances and capacities that can be assigned in the equivalent circuit following a least squares analysis of the data describe changes that occur on the corroding metal surface and in the protective coating. A suitable equivalent circuit was determined that predicts the correct Bode phase and magnitude for the experimental sample. The DC corrosion current density data are related to equivalent circuit element parameters.

Quantum dots conjugated zinc oxide nanosheets: Impeder of microbial growth and biofilm

Energy Technology Data Exchange (ETDEWEB)

Patil, Rajendra [Department of Biotechnology, Savitribai Phule Pune University, Pune 411007 (India); Gholap, Haribhau, E-mail: haribhau.gholap@fergusson.edu [Department of Physics, Fergusson College, Pune 411004 (India); Warule, Sambhaji [Department of Physics, Nowrosjee Wadia College, Pune 411001 (India); Banpurkar, Arun; Kulkarni, Gauri [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Gade, Wasudeo, E-mail: wngade@unipune.ac.in [Department of Biotechnology, Savitribai Phule Pune University, Pune 411007 (India)

2015-01-30

Graphical abstract: The visible light upon incident on ZnO/CdTe initiate the phenomenon of photocatalytical impedance of biofilm. - Highlights: • Synthesis of efficient light photocatalyst ZnO/CdTe nanostructures by hydrothermal method. • ZnO/CdTe nanostructures show a good antibacterial activity by action on cell membrane. • ZnO/CdTe nanostructures show a good antibiofilm activity, and also act on the cells inside the biofilm. - Abstract: The grieving problem of the 21st century has been the antimicrobial resistance in pathogenic microorganisms to conventional antibiotics. Therefore, developments of novel antibacterial materials which effectively inhibit or kill such resistant microorganisms have become the need of the hour. In the present study, we communicate the synthesis of quantum dots conjugated zinc oxide nanostructures (ZnO/CdTe) as an impeder of microbial growth and biofilm. The as-synthesized nanostructures were characterized by X-ray diffraction, ultraviolet–visible spectroscopy, photoluminescence spectroscopy, field emission scanning electron microscopy and high resolution transmission electron microscopy. The growth impedance property of ZnO and ZnO/CdTe on Gram positive organism, Bacillus subtilis NCIM 2063 and Gram negative, Escherichia coli NCIM 2931 and biofilm impedance activity in Pseudomonas aeruginosa O1 was found to occur due to photocatalytical action on the cell biofilm surfaces. The impedance in microbial growth and biofilm formation was further supported by ruptured appearances of cells and dettrered biofilm under field emission scanning electron and confocal laser scanning microscope. The ZnO/CdTe nanostructures array synthesized by hydrothermal method has an advantage of low growth temperature, and opportunity to fabricate inexpensive material for nano-biotechnological applications.

Quantum dots conjugated zinc oxide nanosheets: Impeder of microbial growth and biofilm

International Nuclear Information System (INIS)

Patil, Rajendra; Gholap, Haribhau; Warule, Sambhaji; Banpurkar, Arun; Kulkarni, Gauri; Gade, Wasudeo

2015-01-01

Graphical abstract: The visible light upon incident on ZnO/CdTe initiate the phenomenon of photocatalytical impedance of biofilm. - Highlights: • Synthesis of efficient light photocatalyst ZnO/CdTe nanostructures by hydrothermal method. • ZnO/CdTe nanostructures show a good antibacterial activity by action on cell membrane. • ZnO/CdTe nanostructures show a good antibiofilm activity, and also act on the cells inside the biofilm. - Abstract: The grieving problem of the 21st century has been the antimicrobial resistance in pathogenic microorganisms to conventional antibiotics. Therefore, developments of novel antibacterial materials which effectively inhibit or kill such resistant microorganisms have become the need of the hour. In the present study, we communicate the synthesis of quantum dots conjugated zinc oxide nanostructures (ZnO/CdTe) as an impeder of microbial growth and biofilm. The as-synthesized nanostructures were characterized by X-ray diffraction, ultraviolet–visible spectroscopy, photoluminescence spectroscopy, field emission scanning electron microscopy and high resolution transmission electron microscopy. The growth impedance property of ZnO and ZnO/CdTe on Gram positive organism, Bacillus subtilis NCIM 2063 and Gram negative, Escherichia coli NCIM 2931 and biofilm impedance activity in Pseudomonas aeruginosa O1 was found to occur due to photocatalytical action on the cell biofilm surfaces. The impedance in microbial growth and biofilm formation was further supported by ruptured appearances of cells and dettrered biofilm under field emission scanning electron and confocal laser scanning microscope. The ZnO/CdTe nanostructures array synthesized by hydrothermal method has an advantage of low growth temperature, and opportunity to fabricate inexpensive material for nano-biotechnological applications

Agreement Between Bioelectrical Impedance and Dual-Energy X-Ray Absorptiometry to Track Changes in Fat-Free Mass After Resistance Training in Older Women.

Science.gov (United States)

Nascimento, Matheus A; Silva, Danilo R P; Ribeiro, Alex S; Pina, Fábio L C; Gerage, Aline M; Gobbo, Luís A; Mayhew, Jerry L; Cyrino, Edilson S

2018-05-23

Nascimento, MA, Silva, DRP, Ribeiro, AS, Pina, FLC, Gerage, AM, Gobbo, LA, Mayhew, JL, and Cyrino, ES. Agreement between bioelectrical impedance and dual-energy x-ray absorptiometry to track changes in fat-free mass after resistance training in older women. J Strength Cond Res XX(X): 000-000, 2018-The aim of our study was to compare the agreement between bioelectrical impedance (BIA) and dual-energy X-ray absorptiometry (DXA) to track changes on fat-free mass (FFM) after a resistance training (RT) program in older women. Forty-three older women (65.2 ± 4.6 years, 59.5 ± 9.2 kg, 156.4 ± 6.0 cm, 24.3 ± 3.3 kg·m) participated in a RT intervention (12 weeks, 8 exercises, 2 sets, 10-15 repetitions, 3 nonconsecutive days per week). Fat-free mass changes were determined by a single-frequency BIA device (EQ1), 6 BIA prediction equations for older women (EQ2, EQ3, EQ4, EQ5, EQ6, and EQ7), and DXA. At pretraining, 3 equations overpredicted, and 3 underpredicted DXA FFM (F = 244.63, p FFM (F = 176.25, p FFM (0.65 ± 0.82 kg; p FFM. Low correlations between FFM and equation change values suggest that single-frequency BIA-derived equations may not provide sufficient accuracy to track changes in FFM after 12 weeks of RT in older women.

Impedance characteristics of nanoparticle-LiCoO{sub 2}+PVDF

Energy Technology Data Exchange (ETDEWEB)

Panjaitan, Elman, E-mail: elmanp@batan.go.id; Kartini, Evvy, E-mail: kartini@batan.go.id; Honggowiranto, Wagiyo [Center for Science and Technology for Advanced Materials, National Nuclear Energy Agency Kawasan Puspiptek Serpong, Tangerang Selatan15314 (Indonesia)

2016-02-08

The impendance of np-LiCoO{sub 2}+xPVDF, as a cathode material candidate for lithium-ion battery (LIB), has been characterized using impedance spectroscopy for x = 0, 5, 10, 15 and 20 volume percentage (%v/v) and for frequencies in the 42 Hz to 5 MHz range. Both real and imaginary components of the impedance were found to be frequency dependent, and both tend to increase for increasing PVDF (polyvinyilidene fluoride) concentration, except that for 10% PVDF both real and imaginary components of impedance are smaller than for 5%. The mechanism for relaxation time for each addition of PVDF was analyzed using Cole-Cole plots. The analysis showed that the relaxation times of the nanostructured LiCoO{sub 2} with PVDF additive is relatively constant. Further, PVDF addition increases the bulk resistance and decreases the bulk capacitance of the nanostructured LiCoO{sub 2}.

Transcephalic electrical impedance in the study of cerebral circulation in a juvenile pig model.

Science.gov (United States)

Grönlund, J; Bartocci, M; Kääpä, P; Jahnukainen, T; Rautanen, M; Halkola, L; Välimäki, I

1997-11-01

Transcephalic electrical impedance offers a technique for non-invasive, cot-side monitoring of neonatal cerebral circulation but the exact nature of the signal is somewhat ambiguous. The impedance signal is examined in an animal project where the ventilator settings are adjusted (20 min-1-10 min-1-40 min-1 for 10 min periods each) to produce circulatory changes. Six juvenile pigs are intubated, and ECG, arterial blood pressure, carotid flow (CF) by electromagnetic flowmeter and impedance are continuously monitored and stored on analogue tape. Cardiac output by thermodilution, blood oxygen (pO2) and carbon dioxide (pCO2) tensions are measured. ECG is converted to heart rate, mean blood pressure is integrated, and the high-frequency (1.50-4.00 Hz) component of the impedance signal delta Z is computed using autoregressive spectral estimation. Stroke volume, peripheral vascular resistance (PVR) and cerebral vascular resistance (CVR) are calculated. pCO2 and CF increase and pO2 decreases during hypoventilation. CF correlates positively with cardiac output, stroke volume, delta Z and pCO2, and negatively with pO2 and CVR. delta Z correlates positively with heart rate and cardiac output, and negatively with PVR and CVR. It is concluded that the impedance signal is related to the amount of blood transmitted to the brain by every beat of the heart, depending on the changes in both the systemic circulation and the cerebral vascular compliance.

Thioridazine Induces Major Changes in Global Gene Expression and Cell Wall Composition in Methicillin-Resistant Staphylococcus aureus USA300

DEFF Research Database (Denmark)

Thorsing, Mette; Klitgaard, Janne Kudsk; Atilano, Magda L.

2013-01-01

and the transcriptomic response of S. aureus to known inhibitors of cell wall synthesis suggests that TDZ disturbs PGN biosynthesis at a stage that precedes transpeptidation by penicillin-binding proteins (PBPs). In support of this notion, dramatic changes in the muropeptide profile of USA300 were observed following....... In the present study, we have examined the effect of a subinhibitory concentration of TDZ on antimicrobial resistance, the global transcriptome, and the cell wall composition of MRSA USA300. We show that TDZ is able to sensitize the bacteria to several classes of antimicrobials targeting the late stages...... a major impact on the cell wall biosynthesis pathway in S. aureus and provides new insights into how MRSA may be sensitized towards β-lactam antibiotics....

In-Plane Impedance Spectroscopy measurements in Vanadium Dioxide thin films

Science.gov (United States)

Ramirez, Juan; Patino, Edgar; Schmidt, Rainer; Sharoni, Amos; Gomez, Maria; Schuller, Ivan

2012-02-01

In plane Impedance Spectroscopy measurements have been done in Vanadium Dioxide thin films in the range of 100 Hz to 1 MHz. Our measurements allows distinguishing between the resistive and capacitive response of the Vanadium Dioxide films across the metal-insulator transition. A non ideal RC behavior was found in our thin films from room temperature up to 334 K. Around the MIT, an increase of the total capacitance is observed. A capacitor-network model is able to reproduce the capacitance changes across the MIT. Above the MIT, the system behaves like a metal as expected, and a modified equivalent circuit is necessary to describe the impedance data adequately.

Numerical Study of Equilibrium, Stability, and Advanced Resistive Wall Mode Feedback Algorithms on KSTAR

Science.gov (United States)

Katsuro-Hopkins, Oksana; Sabbagh, S. A.; Bialek, J. M.; Park, H. K.; Kim, J. Y.; You, K.-I.; Glasser, A. H.; Lao, L. L.

2007-11-01

Stability to ideal MHD kink/ballooning modes and the resistive wall mode (RWM) is investigated for the KSTAR tokamak. Free-boundary equilibria that comply with magnetic field coil current constraints are computed for monotonic and reversed shear safety factor profiles and H-mode tokamak pressure profiles. Advanced tokamak operation at moderate to low plasma internal inductance shows that a factor of two improvement in the plasma beta limit over the no-wall beta limit is possible for toroidal mode number of unity. The KSTAR conducting structure, passive stabilizers, and in-vessel control coils are modeled by the VALEN-3D code and the active RWM stabilization performance of the device is evaluated using both standard and advanced feedback algorithms. Steady-state power and voltage requirements for the system are estimated based on the expected noise on the RWM sensor signals. Using NSTX experimental RWM sensors noise data as input, a reduced VALEN state-space LQG controller is designed to realistically assess KSTAR stabilization system performance.

The use of electrochemical impedance spectroscopy (EIS) in the evaluation of the electrochemical properties of a microbial fuel cell.

Science.gov (United States)

Manohar, Aswin K; Bretschger, Orianna; Nealson, Kenneth H; Mansfeld, Florian

2008-04-01

Electrochemical impedance spectroscopy (EIS) has been used to determine several electrochemical properties of the anode and cathode of a mediator-less microbial fuel cell (MFC) under different operational conditions. These operational conditions included a system with and without the bacterial catalyst and EIS measurements at the open-circuit potential of the anode and the cathode or at an applied cell voltage. In all cases the impedance spectra followed a simple one-time-constant model (OTCM) in which the solution resistance is in series with a parallel combination of the polarization resistance and the electrode capacitance. Analysis of the impedance spectra showed that addition of Shewanella oneidensis MR-1 to a solution of buffer and lactate greatly increased the rate of the lactate oxidation at the anode under open-circuit conditions. The large decrease of open-circuit potential of the anode increased the cell voltage of the MFC and its power output. Measurements of impedance spectra for the MFC at different cell voltages resulted in determining the internal resistance (R(int)) of the MFC and it was found that R(int) is a function of cell voltage. Additionally, R(int) was equal to R(ext) at the cell voltage corresponding to maximum power, where R(ext) is the external resistance that must be applied across the circuit to obtain the maximum power output.

Correlation between the oxide impedance and corrosion behavior of Zr-Nb-Sn-Fe-Cu alloys

Science.gov (United States)

Park, Sang-Yoon; Lee, Myung-Ho; Jeong, Yong-Hwan; Jung, Youn-Ho

2004-12-01

The correlation between the oxide impedance and corrosion behavior of two series of Zr-Nb-Sn-Fe-Cu alloys was evaluated. Corrosion tests were performed in a 70 ppm LiOH aqueous solution at 360°C for 300 days. The results of the corrosion tests revealed that the corrosion behavior of the alloys depended on the Nb and Sn content. The impedance characteristics for the pre- and post-transition oxide layers formed on the surface of the alloys were investigated in sulfuric acid at room temperature. From the results, a pertinent equivalent circuit model was preferably established, explaining the properties of double oxide layers. The impedance of the oxide layers correlated with the corrosion behavior; better corrosion resistance always showed higher electric resistance for the inner layers. It is thus concluded that a pertinent equivalent circuit model would be useful for evaluating the long-term corrosion behavior of Zr-Nb-Sn-Fe-Cu alloys.

Experimental impedance investigation of an ultracapacitor at different conditions for electric vehicle applications

Science.gov (United States)

Zhang, Lei; Hu, Xiaosong; Wang, Zhenpo; Sun, Fengchun; Dorrell, David G.

2015-08-01

Ultracapacitors (UCs) are being increasingly deployed as a short-term energy storage device in various energy systems including uninterruptable power supplies, electrified vehicles, renewable energy systems, and wireless communication. They exhibit excellent power density and energy efficiency. The dynamic behavior of a UC, however, strongly depends on its impedance characteristics. In this paper, the impedance characteristics of a commercial UC are experimentally investigated through the well-adopted Electrochemical Impedance Spectroscopy (EIS) technique. The implications of the UC operating conditions (i.e., temperature and state of charge (SOC)) to the impedance are systematically examined. The results show that the impedance is highly sensitive to the temperature and SOC; and the temperature effect is more significant. In particular, the coupling effect between the temperature and SOC is illustrated, as well as the high-efficiency SOC window, which is highlighted. To further verify the reliability of the EIS-based investigation and to probe the sensitivity of UC parameters to the operating conditions, a dynamic model is characterized by fitting the collected impedance data. The interdependence of UC parameters (i.e., capacitance and resistance elements) on the temperature and SOC is quantitatively revealed. The impedance-based model is demonstrated to be accurate in two driving-cycle tests.

Effects of multiple modes interaction on the resistive wall mode instability

International Nuclear Information System (INIS)

Chen, Longxi; Lei, Wenqing; Ma, Zhiwei; Wu, Bin

2013-01-01

The effects of multiple modes interaction on the resistive wall mode (RWM) are studied in a slab geometry with and without plasma flow. The modes interaction can have a large effect on both the linear growth rate and the nonlinear saturation level of the RWM. We found that modes interaction can suppress the linear growth rate for the most unstable mode. The plasma flow can also help to control the growth of the RWM. The RWM can be stabilized completely by a plasma flow when considering the modes interaction. The effect of modes interaction on the RWM is stronger for the mode rational surface in the vacuum than that in the plasma. The modes interaction results in a substantially lowered saturation level for the most unstable RWM. (paper)

Effect of Intravenous Infusion Solutions on Bioelectrical Impedance Spectroscopy.

Science.gov (United States)

Yap, Jason; Rafii, Mahroukh; Azcue, Maria; Pencharz, Paul

2017-05-01

Bioelectrical impedance (BIA) is often used to measure body fluid spaces and thereby body composition. However, in acute animal studies, we found that impedance was driven by the saline content of intravenous (IV) fluids and not by the volume. The aim of the study was to investigate the effect of 3 different fluids acutely administered on the change in impedance, specifically resistance (R). Nine healthy adults participated in 3 treatment (0.9% saline, 5% dextrose, and a mixture of 0.3% saline + 3.3% dextrose) experiments on nonconsecutive days. They all received 1 L of one of the treatments intravenously over a 1-hour period. Repeated BIA measurements were performed prior to IV infusion and then every 5 minutes for the 1-hour infusion period, plus 3 more measurements up to 15 minutes after the completion of the infusion. The change in R in the 0.9% saline infusion experiment was significantly lower than that of the glucose and mixture treatment ( P < .001). Bioelectrical impedance spectroscopy and BIA measure salt rather than the volume changes over the infusion period. Hence, in patients receiving IV fluids, BIA of any kind (single frequency or multifrequency) cannot be used to measure body fluid spaces or body composition.

Recovery of BMIPP uptake and regional wall motion in insulin resistant patients following angioplasty for acute myocardial infarction.

Science.gov (United States)

Fujino, Takayuki; Ishii, Yoshinao; Takeuchi, Toshiharu; Hirasawa, Kunihiko; Tateda, Kunihiko; Kikuchi, Kenjiro; Hasebe, Naoyuki

2003-09-01

The effect of insulin resistance (IR) on the fatty acid metabolism of myocardium, and therefore on the recovery of left ventricular (LV) wall motion, has not been established in patients with acute myocardial infarction (AMI). A total of consecutive 58 non-diabetic AMI patients who had successfully undergone emergency coronary angioplasty were analyzed retrospectively. They were categorized into 2 groups, normal glucose tolerance (NGT) and impaired glucose tolerance (IGT), based on a 75-g oral glucose tolerance test (OGTT). The parameters of OGTT, myocardial scintigraphy (n=58) (thallium-201 (Tl) and iodine-123-beta-methyl-iodophenylpentadecanoic acid (BMIPP)) and left ventriculography (n=24) were compared in the 2 groups after reperfusion (acute phase) and 3-4 weeks after the AMI (chronic phase). The insulin resistance (IR), estimated by the serum concentration of insulin at 120 min (IRI 120') of the OGTT and by the HOMA (the homeostasis model assessment) index, was higher in the IGT group than in NGT group. An inverse correlation was found between the recovery of regional LV wall motion in the ischemic lesion and the IRI 120' and HOMA index. Although the recovery of BMIPP uptake from the acute to the chronic phase was higher in the IGT group, it was only correlated with the degree of IRI 120', not with the HOMA. IR accompanied by IGT can negatively influence the recovery of regional LV wall motion.

A Study on the Optimal Receiver Impedance for SNR Maximization in Broadband PLC

Directory of Open Access Journals (Sweden)

Massimo Antoniali

2013-01-01

Full Text Available We consider the design of the front-end receiver for broadband power line communications. We focus on the design of the input impedance that maximizes the signal-to-noise ratio (SNR at the receiver. We show that the amplitude, rather than the power, of the received signal is important for communication purposes. Furthermore, we show that the receiver impedance impacts the amplitude of the noise term. We focus on the background noise, and we propose a novel description of the noise experienced at the receiver port of a PLC network. We model the noise as the sum of four uncorrelated contributions, that is, the active, resistive, receiver, and coupled noise components. We study the optimal impedance design problem for real in-home grids that we assessed with experimental measurements. We describe the results of the measurement campaign, and we report the statistics of the optimal impedance. Hence, we study the best attainable performance when the optimal receiver impedance is deployed. We focus on the SNR and the maximum achievable rate, and we show that power matching is suboptimal with respect to the proposed impedance design approach.

Bioelectrical impedance spectroscopy as a fluid management system in heart failure

International Nuclear Information System (INIS)

Weyer, Sören; Wartzek, Tobias; Leicht, Lennart; Leonhardt, Steffen; Zink, Matthias Daniel; Mischke, Karl; Vollmer, Thomas

2014-01-01

Episodes of hospitalization for heart failure patients are frequent and are often accompanied by fluid accumulations. The change of the body impedance, measured by bioimpendace spectroscopy, is an indicator of the water content. The hypothesis was that it is possible to detect edema from the impedance data. First, a finite integration technique was applied to test the feasibility and allowed a theoretical analysis of current flows through the body. Based on the results of the simulations, a clinical study was designed and conducted. The segmental impedances of 25 patients suffering from heart failure were monitored over their recompensation process. The mean age of the patients was 73.8 and their mean body mass index was 28.6. From these raw data the model parameters from the Cole model were deduced by an automatic fitting algorithm. These model data were used to classify the edema status of the patient. The baseline values of the regression lines of the extra- and intracellular resistance from the transthoracic measurement and the baseline value of the regression line of the extracellular resistance from the foot-to-foot measurement were identified as important parameters for the detection of peripheral edema. The rate of change of the imaginary impedance at the characteristic frequency and the mean intracellular resistance from the foot-to-foot measurement were identified as important parameters for the detection of pulmonary edema. To classify the data, two decision trees were considered: One should detect pulmonary edema (n pulmonary = 13, n none = 12) and the other peripheral edema (n peripheral = 12, n none = 13). Peripheral edema could be detected with a sensitivity of 100% and a specificity of 90%. The detection of pulmonary edema showed a sensitivity of 92.31% and a specificity of 100%. The leave-one-out cross-validation-error for the peripheral edema detection was 12% and 8% for the detection of pulmonary edema. This enables the application of BIS as an

Model-based dynamic resistive wall mode identification and feedback control in the DIII-D tokamak

International Nuclear Information System (INIS)

In, Y.; Kim, J.S.; Edgell, D.H.; Strait, E.J.; Humphreys, D.A.; Walker, M.L.; Jackson, G.L.; Chu, M.S.; Johnson, R.; La Haye, R.J.; Okabayashi, M.; Garofalo, A.M.; Reimerdes, H.

2006-01-01

A new model-based dynamic resistive wall mode (RWM) identification and feedback control algorithm has been developed. While the overall RWM structure can be detected by a model-based matched filter in a similar manner to a conventional sensor-based scheme, it is significantly influenced by edge-localized-modes (ELMs). A recent study suggested that such ELM noise might cause the RWM control system to respond in an undesirable way. Thus, an advanced algorithm to discriminate ELMs from RWM has been incorporated into this model-based control scheme, dynamic Kalman filter. Specifically, the DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] resistive vessel wall was modeled in two ways: picture frame model or eigenmode treatment. Based on the picture frame model, the first real-time, closed-loop test results of the Kalman filter algorithms during DIII-D experimental operation are presented. The Kalman filtering scheme was experimentally confirmed to be effective in discriminating ELMs from RWM. As a result, the actuator coils (I-coils) were rarely excited during ELMs, while retaining the sensitivity to RWM. However, finding an optimized set of operating parameters for the control algorithm requires further analysis and design. Meanwhile, a more advanced Kalman filter based on a more accurate eigenmode model has been developed. According to this eigenmode approach, significant improvement in terms of control performance has been predicted, while maintaining good ELM discrimination

Nonsynchronous Noncommensurate Impedance Transformers

DEFF Research Database (Denmark)

Zhurbenko, Vitaliy; Kim, K

2012-01-01

Nonsynchronous noncommensurate impedance transformers consist of a combination of two types of transmission lines: transmission lines with a characteristic impedance equal to the impedance of the source, and transmission lines with a characteristic impedance equal to the load. The practical...... advantage of such transformers is that they can be constructed using sections of transmission lines with a limited variety of characteristic impedances. These transformers also provide comparatively compact size in applications where a wide transformation ratio is required. This paper presents the data...... matrix approach and experimentally verified by synthesizing a 12-section nonsynchronous noncommensurate impedance transformer. The measured characteristics of the transformer are compared to the characteristics of a conventional tapered line transformer....

Age- and gender-associated differences in electrical impedance values of skeletal muscle

International Nuclear Information System (INIS)

Kortman, Hans G J; Wilder, Sarah C; Geisbush, Tom R; Narayanaswami, Pushpa; Rutkove, Seward B

2013-01-01

Electrical impedance measurements of skeletal muscle may be sensitive to age-associated declines in muscle health. In an effort to evaluate this concept further, we performed electrical impedance myography (EIM) using a handheld array on 38 individuals aged 19–50 years and 41 individuals aged 60–85 years. Individuals either had seven upper extremity or seven lower extremity muscles measured. The 50 kHz reactance, resistance and phase were used as the major outcome variables. Although the phase values were similar in both groups, both reactance and resistance values were lower in the lower extremities of the older individuals as compared to the younger (−23 ± 6%, p = 0.001 for reactance and −27 ± 7%, p = 0.005 for resistance), whereas changes in upper extremity values were not significantly different (−9 ± 5%, p = 0.096 for reactance and +5 ± 9%, p = 0.55 for resistance). When analyzing the genders separately, it became clear that this reduction in lower extremity values was most pronounced in men and less consistently present in women. These findings suggest that age- and gender-associated differences in muscle condition are detectable using EIM. The relationship of these easily obtained parameters to standard functional, imaging, and pathological markers of sarcopenia deserves further study. (paper)

Longitudinal impedance of a step-in for a round beam at arbitrary beam energy

Energy Technology Data Exchange (ETDEWEB)

Al-Khateeb, A.M., E-mail: a.alkhateeb@gsi.d [FAIR-Accelerator Theory Group, GSI Darmstadt, Planckstr. 1, D-64291 Darmstadt (Germany); Boine-Frankenheim, O.; Plotnikov, A. [FAIR-Accelerator Theory Group, GSI Darmstadt, Planckstr. 1, D-64291 Darmstadt (Germany); Shim, S.Y. [FAIR Division, Magnettechnik/Kryotechnik, GSI Darmstadt, Planckstr. 1, D-64291 Darmstadt (Germany); Haenichen, L. [Technische Universitaet Darmstadt, Institut fuer Theorie elektromagnetischer Felder, TEMF, Schlossgartenstr. 8, D-64289 Darmstadt (Germany)

2011-01-21

Contribution of step-in geometric discontinuity to the longitudinal coupling impedance has been obtained analytically using exact field matching. We assumed a perfectly conducting beam-pipe wall of two different radii connected coaxially at z=0 so that the contribution to the longitudinal coupling impedance is purely due to the beam-pipe geometric discontinuity. We also obtained the longitudinal loss factor for a Gaussian beam as a function of beam energy and bunch length. Results have been analyzed numerically for some representative parameters close to real machine parameters. Analytical results have also been compared with numerical simulation from CST at relativistic beam energies. We found a very good agreement between theory and simulation.

Experimental investigations on frictional resistance and velocity distribution of rough wall with regularly distributed triangular ribs

International Nuclear Information System (INIS)

Motozawa, Masaaki; Ito, Takahiro; Iwamoto, Kaoru; Kawashima, Hideki; Ando, Hirotomo; Senda, Tetsuya; Tsuji, Yoshiyuki; Kawaguchi, Yasuo

2013-01-01

Highlights: • Flow over the regularly distributed triangular ribs was investigated. • Simultaneous measurement of flow resistance and velocity profile was performed. • Flow resistance was measured directly and velocity profile was measured by LDV. • Flow resistance was estimated by the information of the velocity field. • Estimated flow resistance has good agreement with the measured flow resistance. -- Abstract: The relationship between the flow resistance of a turbulent flow over triangular ribs regularly distributed on a wall surface and the velocity distribution around the ribs was investigated experimentally. A concentric cylinder device composed of an inner test cylinder and an outer cylinder was employed to measure the flow resistance using the torque of the shaft of the inner cylinder and the velocity distribution of the flow around a rib by laser Doppler velocimetry (LDV) simultaneously. We prepared four inner test cylinders having 4, 8, 12 and 16 triangular ribs on the surface with the same interval between them. Each rib had an isosceles right triangle V-shape and a height of 2 mm. To investigate the relationship between flow resistance and velocity distribution, we estimated the frictional drag and pressure drag acting on the surface of the ribs separately using the velocity distribution. Therefore, we could also estimate the total flow resistance using the velocity distribution. As a result of the experiment, the flow resistance and the attachment point downstream of the rib were shown to depend on the distance between ribs. Moreover, the flow resistance estimated using the velocity distribution had good agreement with the flow resistance measured using the torque of the inner cylinder

Polynomial Collocation for Handling an Inaccurately Known Measurement Configuration in Electrical Impedance Tomography

DEFF Research Database (Denmark)

Hyvönen, Niina; Kaarnioja, V.; Mustonen, L.

2017-01-01

The objective of electrical impedance tomography is to reconstruct the internal conductivity of a physical body based on measurements of current and potential at a finite number of electrodes attached to its boundary. Although the conductivity is the quantity of main interest in impedance...... tomography, a real-world measurement configuration includes other unknown parameters as well: The information on the contact resistances, electrode positions, and body shape is almost always incomplete. In this work, the dependence of the electrode measurements on all aforementioned model properties...

Adaptive optimal stochastic state feedback control of resistive wall modes in tokamaks

International Nuclear Information System (INIS)

Sun, Z.; Sen, A.K.; Longman, R.W.

2006-01-01

An adaptive optimal stochastic state feedback control is developed to stabilize the resistive wall mode (RWM) instability in tokamaks. The extended least-square method with exponential forgetting factor and covariance resetting is used to identify (experimentally determine) the time-varying stochastic system model. A Kalman filter is used to estimate the system states. The estimated system states are passed on to an optimal state feedback controller to construct control inputs. The Kalman filter and the optimal state feedback controller are periodically redesigned online based on the identified system model. This adaptive controller can stabilize the time-dependent RWM in a slowly evolving tokamak discharge. This is accomplished within a time delay of roughly four times the inverse of the growth rate for the time-invariant model used

Arabidopsis wat1 (walls are thin1)-mediated resistance to the bacterial vascular pathogen, Ralstonia solanacearum, is accompanied by cross-regulation of salicylic acid and tryptophan metabolism

NARCIS (Netherlands)

Denancé, N.; Ranocha, P.; Oria, N.; Barlet, X.; Rivière, M.P.; Yadeta, K.A.; Hoffmann, L.; Perreau, F.; Clément, G.; Maia-Grondard, A.; Berg, van den G.C.M.; Savelli, B.; Fournier, S.; Aubert, Y.; Pelletier, S.; Thomma, B.P.H.J.; Molina, A.; Jouanin, L.; Marco, Y.; Goffner, D.

2013-01-01

Inactivation of Arabidopsis WAT1 (Walls Are Thin1), a gene required for secondary cell-wall deposition, conferred broad-spectrum resistance to vascular pathogens, including the bacteria Ralstonia solanacearum and Xanthomonas campestris pv. campestris, and the fungi Verticillium dahliae and

Electrochemical impedance spectroscopic investigation of the role of alkaline pre-treatment in corrosion resistance of a silane coating on magnesium alloy, ZE41

Energy Technology Data Exchange (ETDEWEB)

Chakraborty Banerjee, P. [Department of Chemical Engineering, Monash University, Clayton, VIC-3800 (Australia); CAST Cooperative Research Centre, Hawthorn, VIC-3122 (Australia); Singh Raman, R.K., E-mail: raman.singh@eng.monash.edu.a [Department of Chemical Engineering, Monash University, Clayton, VIC-3800 (Australia); Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC-3800 (Australia)

2011-04-15

The protective performance of the coatings of bis-1,2-(triethoxysilyl) ethane (BTSE) on ZE41 magnesium alloy with different surface pre-treatments were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.1 M sodium chloride solution. Electrical equivalent circuits were developed based upon hypothetical corrosion mechanisms and simulated to correspond to the experimental data. The morphology and cross section of the alloy subjected to different pre-treatments and coatings were characterized using scanning electron microscope. A specific alkaline pre-treatment of the substrate prior to the coating has been found to improve the corrosion resistance of the alloy.

Electrochemical impedance spectroscopic investigation of the role of alkaline pre-treatment in corrosion resistance of a silane coating on magnesium alloy, ZE41

International Nuclear Information System (INIS)

Chakraborty Banerjee, P.; Singh Raman, R.K.

2011-01-01

The protective performance of the coatings of bis-1,2-(triethoxysilyl) ethane (BTSE) on ZE41 magnesium alloy with different surface pre-treatments were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.1 M sodium chloride solution. Electrical equivalent circuits were developed based upon hypothetical corrosion mechanisms and simulated to correspond to the experimental data. The morphology and cross section of the alloy subjected to different pre-treatments and coatings were characterized using scanning electron microscope. A specific alkaline pre-treatment of the substrate prior to the coating has been found to improve the corrosion resistance of the alloy.

Analytical modelling of resistive wall mode stabilization by rotation in toroidal tokamak plasmas

International Nuclear Information System (INIS)

Ham, C J; Gimblett, C G; Hastie, R J

2011-01-01

Stabilization of the resitive wall mode (RWM) may allow fusion power to be doubled for a given magnetic field in advanced tokamak operation. Experimental evidence from DIII-D and other machines suggests that plasma rotation can stabilize the RWM. Several authors (Finn 1995 Phys. Plasmas 2 3782, Bondeson and Xie 1997 Phys. Plasmas 4 2081) have constructed analytical cylindrical models for the RWM, but these do not deal with toroidal effects. The framework of Connor et al (1988 Phys. Fluids 31 577) is used to develop ideal plasma analytic models with toroidicity included. Stepped pressure profiles and careful ordering of terms are used to simplify the analysis. First, a current driven kink mode model is developed and a dispersion relation for arbitrary current profile is calculated. Second, the external pressure driven kink mode is similarly investigated as the most important RWM arises from this mode. Using this latter model it is found that the RWM is stabilized by Alfven continuum damping with rotation levels similar to those seen in experiments. An expression for the stability of the external kink mode for more general current profiles and a resistive wall is derived in the appendix.

Forced convection heat transfer in rectangular ducts - general case of wall resistances and peripheral conduction for ventilation cooling of nuclear waste repositories

International Nuclear Information System (INIS)

Lyczkowski, R.W.; Solbrig, C.W.; Gidaspow, D.

1982-01-01

A numerical solution for laminar flow heat transfer between a flowing gas and its containing rectangular duct has been obtained for many different boundary conditions which may arise in nuclear waste repository ventilation corridors. The problem has been solved for the cases of insulation on no walls, one wall, two walls, and three walls with various finite resistances on the remaining walls. Simplifications are made to decouple the convective heat transfer problem from the far field conduction problem, but peripheral conduction is retained. Results have been obtained for several duct aspect ratios in the thermal entrance and in the fully developed regions, including the constant temperature cases. When one wall is insulated and the other three are at constant temperature, the maximum temperature occurs in the fluid rather than on the insulated wall. This maximum moves toward the insulated wall with increasing axial distance. Nusselt numbers for the same constant flux on all four walls with peripheral conduction lie in a narrow band bounded by zero and infinite peripheral conduction cases. A dimensionsless wall conduction group of four can be considered infinite for the purpose of estimating fully developed Nusselt numbers to within an accuracy of 3%. A decrease in wall and bulk temperatures by finite wall conduction has been demonstrated for the case of a black body radiation boundary condition. Nusselt numbers for the case of constant temperature on the top and bottom walls and constant heat flux on the side walls exhibited unexpected behavior. (orig.)

Forced convection heat transfer in rectangular ducts - general case of wall resistances and peripheral conduction for ventilation cooling of nuclear waste repositories

International Nuclear Information System (INIS)

Lyczkowski, R.W.; Solbrig, C.W.; Gidaspow, D.

1980-01-01

A numerical solution for laminar flow heat transfer between a flowing gas and its containing rectangular duct has been obtained for many different boundary conditions which may arise in nuclear waste repository ventilation corridors. The problem has been solved for the cases of insulation on no walls, one wall, two walls, and three walls with various finite resistances on the remaining walls. Simplifications are made to decouple the convective heat transfer problem for the far field conduction problem, but peripheral conduction is retained. Results have been obtained for several duct aspect ratios in the thermal entrance and in the fully developed regions, including the constant temperature cases. When one wall is insulated and the other three are at constant temperature, the maximum temperature occurs in the fluid rather than on the insulated wall. This maximum moves toward the insulated wall with increasing axial distance. Nusselt numbers for the same constant flux on all four walls with peripheral conduction lie in a narrow band bounded by zero and infinite peripheral conduction cases. A dimensionless wall conduction group of four can be considered infinite for the purpose of estimating fully developed Nusselt numbers to within an accuracy of 3%. A decrease in wall and bulk temperatures by finite wall conduction has been demonstrated for the case of a black body radiation boundary condition. Nusselt numbers for the case of constant temperature on the top and bottom walls and constant heat flux on the side walls exhibited unexpected behavior

Forced convection heat transfer in rectangular ducts - general case of wall resistances and peripheral conduction for ventilation cooling of nuclear waste repositories

Energy Technology Data Exchange (ETDEWEB)

Lyczkowski, R W [Institute of Gas Technology, Chicago, IL (USA); Solbrig, C W [EG and G Idaho, Inc., Idaho Falls (USA); Gidaspow, D [Illinois Inst. of Tech., Chicago (USA). Dept. of Chemical Engineering

1982-02-01

A numerical solution for laminar flow heat transfer between a flowing gas and its containing rectangular duct has been obtained for many different boundary conditions which may arise in nuclear waste repository ventilation corridors. The problem has been solved for the cases of insulation on no walls, one wall, two walls, and three walls with various finite resistances on the remaining walls. Simplifications are made to decouple the convective heat transfer problem from the far field conduction problem, but peripheral conduction is retained. Results have been obtained for several duct aspect ratios in the thermal entrance and in the fully developed regions, including the constant temperature cases. When one wall is insulated and the other three are at constant temperature, the maximum temperature occurs in the fluid rather than on the insulated wall. This maximum moves toward the insulated wall with increasing axial distance. Nusselt numbers for the same constant flux on all four walls with peripheral conduction lie in a narrow band bounded by zero and infinite peripheral conduction cases. A dimensionsless wall conduction group of four can be considered infinite for the purpose of estimating fully developed Nusselt numbers to within an accuracy of 3%. A decrease in wall and bulk temperatures by finite wall conduction has been demonstrated for the case of a black body radiation boundary condition. Nusselt numbers for the case of constant temperature on the top and bottom walls and constant heat flux on the side walls exhibited unexpected behavior.

Bench measurements of coupling impedance of AGS Booster components

International Nuclear Information System (INIS)

Ratti, A.; Shea, T.J.

1991-01-01

Quantifying instability thresholds for modern synchrotrons and storage rings requires some knowledge of the accelerator's coupling impedance. To this end, the wire technique has been implemented to measure the longitudinal coupling impedance of AGS Booster devices. The techniques are being refined to allow measurement of RHIC devices at higher frequencies. All the measurements are performed using an HP 8753 Network Analyzer controlled via GPIB by a Macintosh computer. The computer provides an environment for automated data acquisition, data analysis, and report generation. Resistive matches between the 50ω analyzer cables and the 300ω pipe-and-wire structure allow the use of a simple response calibration in the measurement of S21 to 400MHz. Results from ferrite loaded rf cavities, position monitors and kickers are presented. 4 refs., 4 figs

Compensating for evanescent modes and estimating characteristic impedance in waveguide acoustic impedance measurements

DEFF Research Database (Denmark)

Nørgaard, Kren Rahbek; Fernandez Grande, Efren

2017-01-01

The ear-canal acoustic impedance and reflectance are useful for assessing conductive hearing disorders and calibrating stimulus levels in situ. However, such probe-based measurements are affected by errors due to the presence of evanescent modes and incorrect estimates or assumptions regarding...... characteristic impedance. This paper proposes a method to compensate for evanescent modes in measurements of acoustic impedance, reflectance, and sound pressure in waveguides, as well as estimating the characteristic impedance immediately in front of the probe. This is achieved by adjusting the characteristic...... impedance and subtracting an acoustic inertance from the measured impedance such that the non-causality in the reflectance is minimized in the frequency domain using the Hilbert transform. The method is thus capable of estimating plane-wave quantities of the sought-for parameters by supplying only...

Impedance cardiography – optimization and efficacy evaluation of antihypertensive treatment

Directory of Open Access Journals (Sweden)

Katarzyna Panasiuk-Kamińska

2016-09-01

Full Text Available Background . Hypertension is a civilization disease which currently affects about 10.5 m people in Poland. The number of patients with diagnosed, untreated hypertension amounts to 18%, and as many as 45% of patients are treated ineffectively whereas only 26% are treated effectively. Impedance cardiography (IC is an important tool both in diagnostics and the treatment of hypertensive patients, particularly in the case of antihypertensive treatment resistance. This method allows for the individualized treatment of each patient on the basis of hemodynamic parameters, monitoring of hypertensive patients in the outpatient care setting, and the assessment of cardiovascular risk factors. Objectives . The aim of the study was to evaluate the efficacy of hypotensive medications in patients with hypertension using impedance cardiography. Material and methods. The study involved 60 hypertensive patients, treated with antihypertensives, who failed to achieve the required blood pressure values. The modification of hypertension therapy was based on EBM (evidence-based medicine and on hemodynamic parameters obtained using impedance cardiography. Results . It was found that high blood pressure therapy based on impedance cardiography parameters has a significant influence on blood pressure reduction compared to EM B-based therapy: below 140/90: 66.8 vs. 55.1% and below 130/80: 23.5 vs. 18.9%. Conclusions . On the basis of this study it was confirmed that impedance cardiography allows for a significant reduction of hypertension and the selection of the most effective therapeutic strategy, providing for the optimization and efficacy of hypertension treatment.

Investigation of body's impedance under different conditions for electro-acupuncture

International Nuclear Information System (INIS)

Ahmed, M.M.; Abrarov, S.; Khan, R.R.; Maqsood, R.S.; Qaiser, M.A.; Karimov, Kh. S.

2001-01-01

A computer controlled automated setup has been designed to investigate the body acupuncture points (bio-active points) by using a probes matrix which exerts a uniform pressure on the body. 16 probes matrix was placed in a 15 : 15 mm/sup 2/ dielectric substrate with 5 mm inter probe distance, compatible with the average diameter of the points. These probes have been designed to facilitate a semiconductor injection laser for probing of the points along with optical and/or electric signal. The bioactive points were identified by evaluating the impedance between each probe and a hand held electrode through a micro-controlled scan. This also allowed the selection of an appropriate signal - DC, AC or tidal waveform, for the electric treatment of bioactive points. It has been found that body impedance decreases with the increase of measuring voltage. Moreover, for current-voltage characteristics a nonlinearity coefficient in the range 2-3 was also observed. The study revealed that at low applied voltages 0.l V, the impedance depends on the polarity of the applied signal. Furthermore, body impedance decreases nonlinearly by increasing the probe's pressure on the skin, which may be attributed to piezo resistive effect. By using the AC and Dc measurements an appropriate body equivalent circuit is proposed in this investigation. (author)

Resistive theory of bunch lengthening

International Nuclear Information System (INIS)

Month, M.; Messerschmid, E.

1977-01-01

A new theory of bunch lengthening in electron storage rings is proposed. The equilibrium bunch length is that length which stabilizes the bunch against the onset of ''fast'' resistive instability, caused by the combination of many high frequency resonators such as vacuum flanges. The heat dissipated in these impedance sources follows immediately from the bunch length. It is found that the anomalous bunch length is determined by a scaling parameter g = (hVcos phi/sub s/)/I. Data taken in SPEAR I and II, data in which g extends in value by more than three orders of magnitude, can be fit with an appropriate choice of high frequency, large width coupling impedance. The impedance functions for SPEAR I and II are taken to be the same, a reflection of the fact that the high frequency sources are chamber discontinuities rather than structures connected with the rf systems. A parameter search leads to an impedance characterized by a central frequency approximately 5 GHz, a width (FWHM) approximately 1.8 GHz and a peak impedance approximately 0.2 M OMEGA. The expected and observed higher mode resistance (i.e., heat dissipated) for SPEAR are compared and found to be in agreement. Predictions are given for PEP and PETRA

Selective virtual capacitive impedance loop for harmonics voltage compensation in islanded microgrids

DEFF Research Database (Denmark)

Micallef, Alexander; Apap, Maurice; Spiteri-Staines, Cyril

2013-01-01

Parallel inverters having LCL output filters cause voltage distortions at the point of common coupling (PCC) in islanded microgrids when non-linear loads are present. A capacitive virtual impedance loop could be used to provide selective harmonic compensation in islanded microgrids, instead of in...... resistance for selective harmonic compensation in islanded microgrids. Simulation results were given to show the suitability of the proposed algorithms in reducing the voltage harmonics at the PCC.......Parallel inverters having LCL output filters cause voltage distortions at the point of common coupling (PCC) in islanded microgrids when non-linear loads are present. A capacitive virtual impedance loop could be used to provide selective harmonic compensation in islanded microgrids, instead...... of introducing additional active or passive filters into the system that could compromise the stability of the microgrid. However, the performance of these compensation loops becomes degraded when a virtual resistance is introduced with the aim to improve the overall stability of the parallel inverters...

On the roles of direct feedback and error field correction in stabilizing resistive-wall modes

International Nuclear Information System (INIS)

In, Y.; Bogatu, I.N.; Kim, J.S.; Garofalo, A.M.; Jackson, G.L.; La Haye, R.J.; Schaffer, M.J.; Strait, E.J.; Lanctot, M.J.; Reimerdes, H.; Marrelli, L.; Martin, P.; Okabayashi, M.

2010-01-01

Active feedback control in the DIII-D tokamak has fully stabilized the current-driven ideal kink resistive-wall mode (RWM). While complete stabilization is known to require both low frequency error field correction (EFC) and high frequency feedback, unambiguous identification has been made about the distinctive role of each in a fully feedback-stabilized discharge. Specifically, the role of direct RWM feedback, which nullifies the RWM perturbation in a time scale faster than the mode growth time, cannot be replaced by low frequency EFC, which minimizes the lack of axisymmetry of external magnetic fields. (letter)

Pyrolytic carbon microelectrodes for impedance based cell sensing

DEFF Research Database (Denmark)

Hassan, Yasmin Mohamed; Caviglia, Claudia; Hemanth, Suhith

2016-01-01

Electrically conductive glass-like carbon structures can be obtained from a polymer template through a pyrolysis process. These structures can be used as electrodes for bio sensing applications such as electrochemical evaluation of cell adhesion and proliferation. This study focuses on the optimi...... to decrease the resistivity of the resulting carbon material and improve the performance in cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Finally, EIS was used to monitor adhesion and proliferation of HeLa cells....

IMPEDANCE METHOD OF MEASURING OF THE TITRATABLE ACIDITY OF YOGURT

Directory of Open Access Journals (Sweden)

Miroslav Vasilev

2016-10-01

Full Text Available In the present work are analyzed studies related to changes in the active impedance component of the dairy environment caused by the flow of lactic fermentation and coagulation of casein in milk. The aim of this work was to determine the relationship between the relative change of titratable acidity and the relative change of active impedance component of the dairy environment with lactic fermentation, causing coagulation of the casein in milk. . The data were interpolated with cubic spline, visualizing how when the fat content increases, the electrical resistance increases too. All data, collected during the tests would complement and be used for solving the optimization problem to determine the time of completion of the coagulation in future work.

Overexpression of Rice Wall-Associated Kinase 25 (OsWAK25) Alters Resistance to Bacterial and Fungal Pathogens

Science.gov (United States)

Harkenrider, Mitch; Sharma, Rita; De Vleesschauwer, David; Tsao, Li; Zhang, Xuting; Chern, Mawsheng; Canlas, Patrick; Zuo, Shimin; Ronald, Pamela C.

2016-01-01

Wall-associated kinases comprise a sub-family of receptor-like kinases that function in plant growth and stress responses. Previous studies have shown that the rice wall-associated kinase, OsWAK25, interacts with a diverse set of proteins associated with both biotic and abiotic stress responses. Here, we show that wounding and BTH treatments induce OsWAK25 transcript expression in rice. We generated OsWAK25 overexpression lines and show that these lines exhibit a lesion mimic phenotype and enhanced expression of rice NH1 (NPR1 homolog 1), OsPAL2, PBZ1 and PR10. Furthermore, these lines show resistance to the hemibiotrophic pathogens, Xanthomonas oryzae pv. oryzae (Xoo) and Magnaporthe oryzae, yet display increased susceptibility to necrotrophic fungal pathogens, Rhizoctonia solani and Cochliobolus miyabeanus. PMID:26795719

Extraction of electrical characteristics from pixels of multifrequency electrical impedance tomographs

International Nuclear Information System (INIS)

Fitzgerald, A.J.; Thomas, B.J.; Cornish, B.H.; Michael, G.J.

1996-01-01

Full text: Multi-frequency electrical impedance tomography (MFEIT) is a modality that provides images of the change in the electrical response of tissue at a number of discrete frequencies relative to the response at a selected reference frequency (H Griffiths and A Ahmed, Clin. Phys. Physiol. Meas. 8A:103-107, 1987). This method overcomes the need, when forming in vivo static images, to measure or calculate the voltage profiles of a resistive, homogeneous reference medium and therefore avoids the errors introduced due to boundary shape and electrode location inaccuracies. Information on the spectral response of the tissue is contained within the pixel values, hence characteristics of the tissues and the state of health can be obtained by extracting this information from in vivo MFEIT images. Griffith and Jossinet (Physiol Meas. 15A: 59-63, 1994) used computer modelling to demonstrate that the Cole-Cole plot (variations of resistance and reactance with frequency) can be extracted from pixel values of MFEIT images provided the reference set was obtained from a purely resistive and homogeneous medium. To date it has not been possible to extract true Cole-Cole plots from in vivo MFEIT images because tissue contains a reactive component of impedance which introduces an unknown phase angle into the reference data set. Instead, an impedance spectrum, equivalent to a Cole-Cole plot rotated about the origin by the unknown phase angle, may be extracted. A correction for this rotation of the Cole-Cole plot is necessary since parameters derived from the impedance spectrum do not accurately reflect the electrical response of the imaged tissue. We have developed two distinct methods to determine this unknown phase angle and hence enable the extraction of parameters that more accurately reflect the true electrical response of tissue from in vivo MFEIT images. The first method is an empirical method based on observation of the distribution of frequency data around the Cole

A-Source Impedance Network

DEFF Research Database (Denmark)

Siwakoti, Yam Prasad; Blaabjerg, Frede; Galigekere, Veda Prakash

2016-01-01

A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance S...

Electrical characterization and impedance response of lanthanum doped barium titanate ceramics

Directory of Open Access Journals (Sweden)

Mančić D.

2008-01-01

Full Text Available The dielectric permittivity and dissipation factor of La-doped and undoped BaTiO3 were investigated as a function of frequency and temperature. The impedance response was used to study the electrical properties of La-doped BaTiO3 over the temperature range from room temperature (RT to 350°C. La-doped and undoped BaTiO3, obtained by a modified Pechini method, were sintered in air at 1300°C for 2 and 16 hours. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE. The most suitable electrical circuit for the interpretation of experimental results is found to be the equivalent circuit consisting of resistors and CPE elements which replace the capacitor elements. The contribution of grain boundary resistance to the total resistance of a system is remarkable at low temperature. Dielectric permittivity of doped BaTiO3 was in the range of 8000 to 12000 at 1 kHz and the dissipation factor was less than 1%.

Seismic Performance of Precast Polystyrene RC Walls

Directory of Open Access Journals (Sweden)

Wibowo Ari

2017-01-01

Full Text Available Precast concrete structure such as precast wall is a concept that is growing rapidly these days. However, the earthquake resistance is believed to be one of its drawbacks. Additionally, the large weight of solid elements also increase the building weight significantly which consequently increase the earthquake base shear force as well. Therefore, investigation on the seismic performance of precast concrete wall has been carried out. Three RC wall specimens using wire mesh reinforcement and EPS (Extended Polystyrene System panel have been tested. This wall was designed as a structural wall that was capable in sustaining lateral loads (in-plane yet were lightweight to reduce the total weight of the building. Parameter observed was the ratio of height to width (aspect ratio of wall of 1.0, 1.5 and 2.0 respectively with the aim to study the behaviour of brittle to ductile transition of the wall. Incremental static load tests were conducted until reaching peak load and then followed by displacement control until failure. Several data were measured at every stage of loading comprising lateral load-displacement behaviour, ultimate strength and collapse mechanism. The outcomes showed that precast concrete walls with a steel wire and EPS panel filler provided considerably good resistance against lateral load.

Development of an enrofloxacin immunosensor based on label-free electrochemical impedance spectroscopy.

Science.gov (United States)

Wu, Ching-Chou; Lin, Chia-Hung; Wang, Way-Shyan

2009-06-30

Enrofloxacin is the most widespread antibiotic in the fluoroquinolone family. As such, the development of a rapid and sensitive method for the determination of trace amounts of enrofloxacin is an important issue in the health field. The interaction of the enrofloxacin antigen to a specific antibody (Ab) immobilized on an 11-mercapto-undecanoic acid-coated gold electrode was quantified by electrochemical impedance spectroscopy. Two equivalent circuits were separately used to interpret the obtained impedance spectra. These circuits included one resistor in series with one parallel circuit comprised of a resistor and a capacitor (1R//C), and one resistor in series with two parallel RC circuits (2R//C). The results indicate that the antigen-antibody reaction analyzed using the 1R//C circuit provided a more sensitive resistance increment against the enrofloxacin concentration than that of the 2R//C circuit. However, the 2R//C circuit provided a better fitting for impedance spectra, and therefore supplies more detailed results of the enrofloxacin-antibody interaction, causing the increase of electron transfer resistance selectively to the modified layer, and not the electrical double layer. The antibody-modified electrode allowed for analysis of the dynamic linear range of 1-1000 ng/ml enrofloxacin with a detection limit of 1 ng/ml. The reagentless and label-free impedimetric immunosensors provide a simple and sensitive detection method for the specific determination of enrofloxacin.

Fast FPGA Implementation of an Original Impedance Analyser

Directory of Open Access Journals (Sweden)

Abdulrahman HAMED

2011-02-01

Full Text Available This article describes in detail the design and rapid prototyping of an embedded impedance analyzer. The measurement principle is based on the feedback control of the excitation voltage VD during a fast frequency sweeping. This function is carried out by a high precision synthesizer whose output resistance RG is digitally adjustable. Real and imaginary parts of the dipole impedance are determined from RG and the phase of VD. The digital architecture design uses the hardware-in-the-loop simulation in which the dipole is modeled using an RLC parallel circuit and a Butterworth Van Dyke structure. All digital functions are implemented on a Stratix II FPGA board with a 100 MHz frequency clock. The parameters taken into account are the frequency range (0 to 5 MHz, speed and resolution of the analysis and the quality factor of the resonant dipole. To reduce the analysis duration, the frequency sweeping rate is adjusted in real time.

An electrochemical impedance model for integrated bacterial biofilms

International Nuclear Information System (INIS)

Ben-Yoav, Hadar; Freeman, Amihay; Sternheim, Marek; Shacham-Diamand, Yosi

2011-01-01

Bacterial cells attachment onto solid surfaces and the following growth into mature microbial biofilms may result in highly antibiotic resistant biofilms. Such biofilms may be incidentally formed on tissues or implanted devices, or intentionally formed by directed deposition of microbial sensors on whole-cell bio-chip surface. A new method for electrical characterization of the later on-chip microbial biofilm buildup is presented in this paper. Measurement of impedance vs. frequency in the range of 100 mHz to 400 kHz of Escherichia coli cells attachment to indium-tin-oxide-coated electrodes was carried out while using optical microscopy estimating the electrode area coverage. We show that impedance spectroscopy measurements can be interpreted by a simple electrical equivalent model characterizing both attachment and growth of the biofilm. The correlation of extracted equivalent electrical lumped components with the visual biofilm parameters and their dependence on the attachment and growth phases is confirmed.

Determination of abdominal fat thickness using dual electrode separation in the focused impedance method (FIM)

International Nuclear Information System (INIS)

Surovy, Nusrat Jahan; Billah, Md Masum; Haowlader, Salahuddin; Al-Quaderi, Golam Dastegir; Rabbani, K Siddique-e

2012-01-01

Subcutaneous fat layer thickness in the abdomen is a risk indicator of several diseases and disorders like diabetes and heart problems and could be used as a measure of fitness. Skinfold measurement using mechanical calipers is simple but prone to error. Ultrasound scanning techniques are yet to be established as accurate methods for this purpose. magnetic resonance imaging (MRI) and computed tomography (CT) scans can provide the answer but are expensive and not available widely. Some initiatives were made earlier to use electrical impedance to this end, but had inadequacies. In the first part of this paper, a 4-electrode focused impedance method (FIM) with different electrode separations has been studied for its possible use in the determination of abdominal fat thickness in a localized region. For this, a saline phantom was designed to provide different electrode separations and different layers of resistive materials adjacent to the electrodes. The background saline simulated the internal organs having low impedance while the resistive layers simulated the subcutaneous fat. The plot of the measured impedance with electrode separation had different ‘slopes’ for different thicknesses of resistive layers, which offered a method to obtain an unknown thickness of subcutaneous fat layer. In the second part, measurements were performed on seven human subjects using two electrode separations. Fat layer thickness was measured using mechanical calipers. A plot of the above ‘slope’ against fat thickness could be fitted using a straight line with an R 2 of 0.93. Then this could be used as a calibration curve for the determination of unknown fat thickness. Further work using more accurate CT and MRI measurements would give a better calibration curve for practical use of this non-invasive and low-cost technique in abdominal fat thickness measurement. (paper)

Impedance and electric modulus analysis of Sm-modified Pb(Zr{sub 0.55}Ti{sub 0.45}){sub 1-x/4}O{sub 3} ceramics

Energy Technology Data Exchange (ETDEWEB)

Ranjan, Rajiv [Department of Physics, J. Co-operative College, Kolhan University, Jharkhand 831036 (India); Kumar, Rajiv [Department of Physics, J. Worker' s College, Kolhan University, Jharkhand 831012 (India); Kumar, Nawnit [Department of Physics and Meteorology, IIT Kharagpur, West Bengal 721302 (India); Behera, Banarji [School of Physics, Sambalpur University, Jyoti Vihar, Bula 768019, Orissa (India); Choudhary, R.N.P., E-mail: crnpfl@gmail.com [Department of Physics, ITER, S.O.A. University, Bhubaneswar 751 013, Orissa (India)

2011-06-02

Highlights: > The PSZT ceramics with samarium were prepared by solid-state reaction technique. > Bulk resistive contribution is found to decrease with the increase in temperature. > PSZT ceramics exhibit NTCR type behavior usually found in semiconductors. > Modulus plots show the presence of grain boundary along with bulk contributions. > Impedance analysis has confirmed the presence of non-Debye type of relaxation. - Abstract: The polycrystalline ceramic samples of Pb{sub 1-x}Sm{sub x}(Zr{sub 0.55}Ti{sub 0.45}){sub 1-x/4}O{sub 3} (x = 0.00, 0.03, 0.06 and 0.09) were prepared by solid-state reaction technique at high temperature. Electric impedance (Z) and modulus (M) properties of the materials have been investigated within a wide range of temperature and frequency using complex impedance spectroscopy (CIS) technique. The complex impedance analysis has suggested the presence of mostly bulk resistive (grain) contributions in the materials. This bulk resistance is found to decrease with the increase in temperature. It indicates that the PSZT compounds exhibit a typical negative temperature coefficient of resistance (NTCR) behavior. The bulk contribution also exhibits an increasing trend with the increase in Sm{sup 3+} substitution to PZT. The complex modulus plots have confirmed the presence of grain (bulk) as well as grain boundary contributions in the materials. Both the complex impedance and modulus studies have suggested the presence of non-Debye type of relaxation in the materials.

Experimental study of the longitudinal instability for beam transport

International Nuclear Information System (INIS)

Reiser, M.; Wang, J.G.; Guo, W.M.; Wang, D.X.

1990-01-01

Theoretical model for beam longitudinal instability in a transport pipe with general wall impedance is considered. The result shows that a capacitive wall tends to stabilize the beam. The experimental study of the instability for a pure resistive-wall is presented, including the design parameters, setup and components for the experiment. 6 refs., 3 figs

Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion

Science.gov (United States)

Bartholomew, Paul D.; Guthrie, W. Spencer; Mazzeo, Brian A.

2012-08-01

Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

Application of electrochemical impedance spectroscopy to monitor seawater fouling on stainless steels and copper alloys

International Nuclear Information System (INIS)

Feron, D.

1991-01-01

Electrochemical impedance spectroscopy may be applied to detect and to follow seawater fouling. Experiments have been conducted with natural seawater flowing inside tube-electrodes at temperatures between 30 deg C and 85 deg C. With stainless steel tubes, mineral and organic foulings have been followed; a linear relationship between the dry weight of the organic fouling and its electrical resistance, has been observed. On copper alloy tubes, only mineral deposits have occurred and so have been detected by impedance spectroscopy. (Author). 5 refs., 6 figs

Microwave and Millimeter Wave Properties of Vertically-Aligned Single Wall Carbon Nanotubes Films

Science.gov (United States)

Haddadi, K.; Tripon-Canseliet, C.; Hivin, Q.; Ducournau, G.; Teo, E.; Coquet, P.; Tay, B. K.; Lepilliet, S.; Avramovic, V.; Chazelas, J.; Decoster, D.

2016-05-01

We present the experimental determination of the complex permittivity of vertically aligned single wall carbon nanotubes (SWCNTs) films grown on quartz substrates in the microwave regime from 10 MHz up to 67 GHz, with the electrical field perpendicular to the main axis of the carbon nanotubes (CNTs), based on coplanar waveguide transmission line approach together with the measurement of the microwave impedance of top metalized vertically—aligned SWCNTs grown on conductive silicon substrates up to 26 GHz. From coplanar waveguide measurements, we obtain a real part of the permittivity almost equal to unity, which is interpreted in terms of low carbon atom density (3 × 1019 at/cm3) associated with a very low imaginary part of permittivity (vertically aligned CNTs bundle equivalent to a low resistance reveals a good conductivity (3 S/cm) parallel to the CNTs axis. From these two kinds of data, we experimentally demonstrate the tensor nature of the vertically grown CNTs bundles.

Ultrahigh impedance method to assess electrostatic accelerator performance

Directory of Open Access Journals (Sweden)

Nikolai R. Lobanov

2015-06-01

Full Text Available This paper describes an investigation of problem-solving procedures to troubleshoot electrostatic accelerators. A novel technique to diagnose issues with high-voltage components is described. The main application of this technique is noninvasive testing of electrostatic accelerator high-voltage grading systems, measuring insulation resistance, or determining the volume and surface resistivity of insulation materials used in column posts and acceleration tubes. In addition, this technique allows verification of the continuity of the resistive divider assembly as a complete circuit, revealing if an electrical path exists between equipotential rings, resistors, tube electrodes, and column post-to-tube conductors. It is capable of identifying and locating a “microbreak” in a resistor and the experimental validation of the transfer function of the high impedance energy control element. A simple and practical fault-finding procedure has been developed based on fundamental principles. The experimental distributions of relative resistance deviations (ΔR/R for both accelerating tubes and posts were collected during five scheduled accelerator maintenance tank openings during 2013 and 2014. Components with measured ΔR/R>±2.5% were considered faulty and put through a detailed examination, with faults categorized. In total, thirty four unique fault categories were identified and most would not be identifiable without the new technique described. The most common failure mode was permanent and irreversible insulator current leakage that developed after being exposed to the ambient environment. As a result of efficient in situ troubleshooting and fault-elimination techniques, the maximum values of |ΔR/R| are kept below 2.5% at the conclusion of maintenance procedures. The acceptance margin could be narrowed even further by a factor of 2.5 by increasing the test voltage from 40 V up to 100 V. Based on experience over the last two years, resistor and

The Impedance of Multi-layer Vacuum Chambers

CERN Document Server

Vos, L

2003-01-01

Many components of the LHC vacuum chamber have multi-layered walls : the copper coated cold beam screen, the titanium coated ceramic chamber of the dump kickers, the ceramic chamber of the injection kickers coated with copper stripes, only to name a few. Theories and computer programs are available for some time already to evaluate the impedance of these elements. Nevertheless, the algorithm developed in this paper is more convenient in its application and has been used extensively in the design phase of multi-layer LHC vacuum chamber elements. It is based on classical transmission line theory. Closed expressions are derived for simple layer configurations, while beam pipes involving many layers demand a chain calculation. The algorithm has been tested with a number of published examples and was verified with experimental data as well.

Out-of-plane behavior of hollow clay tile walls infilled between steel frames

International Nuclear Information System (INIS)

Butala, M.B.; Jones, W.D.; Beavers, J.E.

1991-01-01

Several Buildings at the Department of Energy (DOE) Oak Ridge Y-1 2 Plant rely on unreinforced hollow clay tile walls (HCTW) infilled between unbraced, non-moment resisting steel frames to resist natural phenomena forces, seismic and wind. One critical building relies on moment resisting steel frames in one direction while relying on unreinforced HCTWs infilled between the columns in the orthogonal direction to resist these forces. The HCTWs must act as shear walls while maintaining out-of-plane lateral stability. In assessing the safety of these buildings to seismic forces, several models to study the in- and out-of-plane effects were made and analyzed. The study of the moment resisting steel framed building indicated that bending stresses in the walls were induced by building drift and not by inertial forces per se. The discovery of this phenomenon was some what of a surprise in that the analysis performed is not typically used in design of these structures. The study indicated that the walls began to crack at their interface with the foundation at a low open-quotes gclose quotes level and that horizontal cracking at different elevations continued until the walls exhibited little bending resistance

Impeded Dark Matter

Energy Technology Data Exchange (ETDEWEB)

Kopp, Joachim; Liu, Jia [PRISMA Cluster of Excellence & Mainz Institute for Theoretical Physics,Johannes Gutenberg University,Staudingerweg 7, 55099 Mainz (Germany); Slatyer, Tracy R. [Center for Theoretical Physics, Massachusetts Institute of Technology,Cambridge, MA 02139 (United States); Wang, Xiao-Ping [PRISMA Cluster of Excellence & Mainz Institute for Theoretical Physics,Johannes Gutenberg University,Staudingerweg 7, 55099 Mainz (Germany); Xue, Wei [Center for Theoretical Physics, Massachusetts Institute of Technology,Cambridge, MA 02139 (United States)

2016-12-12

We consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario “Impeded Dark Matter”. We demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.

Impeded Dark Matter

International Nuclear Information System (INIS)

Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei

2016-01-01

We consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario “Impeded Dark Matter”. We demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.

Low Impedance Voice Coils for Improved Loudspeaker Efficiency

DEFF Research Database (Denmark)

Iversen, Niels Elkjær; Knott, Arnold; Andersen, Michael A. E.

2015-01-01

In modern audio systems utilizing switch-mode amplifiers the total efficiency is dominated by the rather poor efficiency of the loudspeaker. For decades voice coils have been designed so that nominal resistances of 4 to 8 Ohms is obtained, despite modern audio amplifiers, using switch-mode techno...... responses are estimated. For this woofer it is shown that the sensitivity can be improved approximately 1 dB, corresponding to a 30% efficiency improvement, just by increasing the fill factor using a low impedance voice coil with rectangular wire....

Observations involving broadband impedance modelling

Energy Technology Data Exchange (ETDEWEB)

Berg, J S [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

1996-08-01

Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)

Impact of SSSC on Measured Impedance in Single Phase to Ground Fault Condition on 220 kV Transmission Line

Directory of Open Access Journals (Sweden)

Mohamed ZELLAGUI

2012-08-01

Full Text Available This paper presents and compares the impact of SSSC on measured impedance for single phase to ground fault condition. The presence of Static Synchronous SSSC on a transmission line has a great influence on the ZRelay in distance protection. The protection of the high voltage 220 kV single circuit transmission line in eastern Algerian electrical transmission networks is affected in the case with resistance fault RF. The paper investigate the effect of Static Synchronous Series Compensator (SSSC on the measured impedance (Relay taking into account the distance fault point (n and fault resistance (RF. The resultants simulation is performed in MATLAB software environment.

Evaluation of impedance on biological Tissues using automatic control measurement system

Energy Technology Data Exchange (ETDEWEB)

Kil, Sang Hyeong; Shin, Dong Hoon; Lee, Seong Mo [Pusan National University, Yangsan (Korea, Republic of); Lee, Moo Seok; Kim, Sang Sik [Pusan National University, Busan (Korea, Republic of); Kim, Gun FDo; Lee, Jong Kyu [Pukyung National University, Busan (Korea, Republic of)

2015-08-15

Each biological tissue has endemic electrical characteristics owing to various differences such as those in cellular arrangement or organization form. The endemic electrical characteristics change when any biological change occurs. This work is a preliminary study surveying the changes in the electrical characteristics of biological tissue caused by radiation exposure. For protection against radiation hazards, therefore the electrical characteristics of living tissue were evaluated after development of the automatic control measurement system using LabVIEW. No alteration of biological tissues was observed before and after measurement of the electrical characteristics, and the biological tissues exhibited similar patterns. Through repeated measurements using the impedance/gain-phase analyzer, the coefficient of variation was determined as within 10%. The reproducibility impedance phase difference in electrical characteristics of the biological tissue did not change, and the tissue had resistance. The absolute value of impedance decreased constantly in proportion to the frequency. It has become possible to understand the electrical characteristics of biological tissues through the measurements made possible by the use of the developed.

Evaluation of impedance on biological Tissues using automatic control measurement system

International Nuclear Information System (INIS)

Kil, Sang Hyeong; Shin, Dong Hoon; Lee, Seong Mo; Lee, Moo Seok; Kim, Sang Sik; Kim, Gun FDo; Lee, Jong Kyu

2015-01-01

Each biological tissue has endemic electrical characteristics owing to various differences such as those in cellular arrangement or organization form. The endemic electrical characteristics change when any biological change occurs. This work is a preliminary study surveying the changes in the electrical characteristics of biological tissue caused by radiation exposure. For protection against radiation hazards, therefore the electrical characteristics of living tissue were evaluated after development of the automatic control measurement system using LabVIEW. No alteration of biological tissues was observed before and after measurement of the electrical characteristics, and the biological tissues exhibited similar patterns. Through repeated measurements using the impedance/gain-phase analyzer, the coefficient of variation was determined as within 10%. The reproducibility impedance phase difference in electrical characteristics of the biological tissue did not change, and the tissue had resistance. The absolute value of impedance decreased constantly in proportion to the frequency. It has become possible to understand the electrical characteristics of biological tissues through the measurements made possible by the use of the developed.

An improved design of virtual output impedance loop for droop-controlled parallel three-phase Voltage Source Inverters

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

2012-01-01

-sequence virtual resistance even in the case of feeding a balanced three-phase load. Furthermore, to adapt to the variety of unbalanced loads, a dynamically-tuned negative-sequence resistance loop is designed, such that a good compromise between the quality of inverter output voltage and the performance of load......The virtual output impedance loop is known as an effective way to enhance the load sharing stability and quality of droop-controlled parallel inverters. This paper proposes an improved design of virtual output impedance loop for parallel three-phase voltage source inverters. In the approach...... sharing can be obtained. Finally, laboratory test results of two parallel three-phase voltage source inverters are shown to confirm the validity of the proposed method....

Triglyceride glucose index and common carotid wall shear stress.

Science.gov (United States)

Tripolino, Cesare; Irace, Concetta; Scavelli, Faustina B; de Franceschi, Maria S; Esposito, Teresa; Carallo, Claudio; Gnasso, Agostino

2014-02-01

Alterations in wall shear stress contribute to both clinical and subclinical atherosclerosis. Several conditions such as hypertension, diabetes, and obesity can impair shear stress, but the role of insulin resistance has never been investigated. The present study was designed to investigate whether insulin resistance assessed by TyG Index associates with wall shear stress in the common carotid artery. One hundred six individuals were enrolled. Blood pressure, lipids, glucose, and cigarette smoking were evaluated. TyG Index was calculated as log[fasting triglycerides × fasting glucose / 2]. Subjects underwent blood viscosity measurement and echo-Doppler evaluation of carotid arteries to calculate wall shear stress. The association between TyG Index and carotid wall shear stress was assessed by simple and multiple regression analyses. TyG Index was significantly and inversely associated with carotid wall shear stress both in simple (r = -0.44, P glucose greater than 100 mg/dL, and triglycerides greater than 150 mg/dL. The present findings suggest that increasing insulin resistance, as assessed by TyG Index, associates with atherosclerosis-prone shear stress reduction in the common carotid artery.

Calculation of effective impedance of polycrystals in weak magnetic fields

International Nuclear Information System (INIS)

Kaganova, I.M.

2006-01-01

We present results for the effective surface impedance tensor (EIT) of polycrystals of metals in a weak uniform magnetic field H. The frequency region corresponds to the region in which the local impedance boundary conditions are applicable. We suppose that the resistivity tensor ρ ik (H) of the single crystal grains out of which the polycrystal is composed, is known up to the terms of O(H 2 ). For polycrystals of metals of arbitrary symmetry, the elements of the EIT can be calculated to the same order in H, even if the tensor ρ ik (H) is strongly anisotropic. As examples, we write down the EIT of polycrystals of (i) cubic metals (ii) metals with ellipsoidal Fermi surfaces, and (iii) metals of tetragonal symmetry whose tensor ρ ik (0) is strongly anisotropic. Although polycrystals are metals that are isotropic on average, in the presence of a uniform magnetic field the structure of the EIT is not the same as the structure of the impedance tensor of an isotropic metal with a spherical Fermi surface. The results cannot be improved either by taking into account higher powers of H, or with respect to the anisotropy of the single crystal grains

Impedance analysis of subwoofer systems

NARCIS (Netherlands)

Berkhoff, Arthur P.

The electrical impedance of four low-frequency loudspeaker systems is analyzed. The expression for this impedance is obtained directly from the acoustical analogous circuit. Formulas are derived for calculating the small-signal parameters from the frequencies of impedance minima and maxima of two

Theory of the low-voltage impedance of superconductor-- p insulator--normal metal tunnel junctions

International Nuclear Information System (INIS)

Lemberger, T.R.

1984-01-01

A theory for the low-voltage impedance of a superconductor-- p insulator--normal metal tunnel junction is developed that includes the effects of charge imbalance and of quasiparticle fluctuations. A novel, inelastic, charge-imbalance relaxation process is identified that is associated with the junction itself. This new process leads to the surprising result that the charge-imbalance component of the dc resistance of a junction becomes independent of the electron-phonon scattering rate as the insulator resistance decreases

Impedance Source Power Electronic Converters

DEFF Research Database (Denmark)

Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming

Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable...... and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key...... features: Comprehensive analysis of the impedance source converter/inverter topologies, including typical topologies and derived topologies. Fully explains the design and control techniques of impedance source converters/inverters, including hardware design and control parameter design for corresponding...

RGD Peptide-Grafted Graphene Oxide as a New Biomimetic Nano interface for Impedance-Monitoring Cell Behaviors

International Nuclear Information System (INIS)

Li, J.; Zheng, L.; Zeng, L.; Zhang, Y.; Jiang, L.; Song, J.; Li, J.; Zheng, L.; Song, J.; Li, J.; Zheng, L.; Song, J.

2016-01-01

A new biomimetic nano interface was constructed by facile grafting the bioactive arginylglycylaspartic acid (RGD) peptide on the graphene oxide (GO) surface through carbodiimide and N-hydroxysuccinimide coupling amidation reaction. The formed RGD-GO nano composites own unique two-dimensional structure and desirable electrochemical performance. The linked RGD peptides could improve GO∼s biocompatibility and support the adhesion and proliferation of human periodontal ligament fibroblasts (HPLFs) on RGD-GO biofilm surface. Furthermore the biologically active RGD-GO nano composites were demonstrated as a potential biomimetic nano interface for monitoring cell bio behaviors by electrochemical impedance spectroscopy (EIS). By analysis of the data obtained from equivalent circuit-fitting impedance spectroscopy, the information related to cell membrane capacitance, cell-cell gap resistance, and cell-electrode interface gap resistance in the process of cell adhesion and proliferation could be obtained. Besides, this proposed impedance-based cell sensor could be used to assess the inhibition effect of the lipopolysaccharide (LPS) on the HPLFs proliferation. Findings from this work suggested that RGD peptide functionalized GO nano materials may be not only applied in dental tissue engineering but also used as a sensor interface for electrochemical detection and analysis of cell behaviors in vitro.

Bioactivity and electrochemical behavior of hydroxyapatite-silicon-multi walled carbon nano-tubes composite coatings synthesized by EPD on NiTi alloys in simulated body fluid

Energy Technology Data Exchange (ETDEWEB)

Khalili, V., E-mail: V_khalili@sut.ac.ir [Department of Materials Engineering, Engineering Faculty, University of Bonab, Bonab (Iran, Islamic Republic of); Khalil-Allafi, J. [Research Center for Advanced Materials and Mineral Processing, Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Frenzel, J.; Eggeler, G. [Institute for Materials, Faculty of Mechanical Engineering, Ruhr-University Bochum, 44801 Bochum (Germany)

2017-02-01

In order to improve the surface bioactivity of NiTi bone implant and corrosion resistance, hydroxyapatite coating with addition of 20 wt% silicon, 1 wt% multi walled carbon nano-tubes and both of them were deposited on a NiTi substrate using a cathodic electrophoretic method. The apatite formation ability was estimated using immersion test in the simulated body fluid for 10 days. The SEM images of the surface of coatings after immersion in simulated body fluid show that the presence of silicon in the hydroxyapatite coatings accelerates in vitro growth of apatite layer on the coatings. The Open-circuit potential and electrochemical impedance spectroscopy were measured to evaluate the electrochemical behavior of the coatings in the simulated body fluid at 37 °C. The results indicate that the compact structure of hydroxyapatite-20 wt% silicon and hydroxyapatite-20 wt% silicon-1 wt% multi walled carbon nano-tubes coatings could efficiently increase the corrosion resistance of NiTi substrate. - Highlights: • The composite coatings of HA, Si and MWCNTs was prepared using electrophoretic deposition. • The presence of 1 wt.% MWCNTs in the HA coating provides more nucleation cites of apatite crystallites in SBF. • The presence of Si in HA coating increases the growth rate of apatite crystallites with the Ca/P atomic ratio of 1.67. • The EIS indicate the compact HA-20%Si and HA-20%Si-1%MWCNTs coatings efficiently increase corrosion resistance of NiTi. • The porous HA and HA-1%MWCNTs do not increase significantly corrosion resistance due to the easy diffusion path.

Beam measurements of the LHC impedance and validation of the impedance model

CERN Document Server

Esteban Müller, J F; Bohl, T; Mounet, N; Shaposhnikova, E; Timko, H

2014-01-01

Different measurements of the longitudinal impedance of the LHC done with single bunches with various intensities and longitudinal emittances during measurement sessions in 2011-2012 are compared with particle simulations based on the existing LHC impedance model. The very low reactive impedance of the LHC, with Im Z=n = 0.08, is not easy to measure. The most sensitive observation is the loss of Landau damping, which shows at which energy bunches become unstable depending on their parameters. In addition, the synchrotron frequency shift due to the reactive impedance was estimated following two methods. Firstly, it was obtained from the peak-detected Schottky spectrum. Secondly, a sine modulation in the RF phase was applied to the bunches of different intensities and the modulation frequency was scanned. In both cases, the synchrotron frequency shift was of the order of the measurement precision.

Lithium-Ion Battery Power Degradation Modelling by Electrochemical Impedance Spectroscopy

DEFF Research Database (Denmark)

Stroe, Daniel-Ioan; Swierczynski, Maciej Jozef; Stroe, Ana-Irina

2017-01-01

This paper investigates the use of the electrochemical impedance spectroscopy (EIS) technique as an alternative to the DC pulses technique for estimating the power capability decrease of Lithium-ion batteries during calendar ageing. Based on results obtained from calendar ageing tests performed...... at different conditions during one to two years, a generalized model that estimates the battery power capability decrease as function of the resistance Rs increase (obtained from EIS) was proposed and successfully verified....

Microwave Impedance Measurement for Nanoelectronics

Directory of Open Access Journals (Sweden)

M. Randus

2011-04-01

Full Text Available The rapid progress in nanoelectronics showed an urgent need for microwave measurement of impedances extremely different from the 50Ω reference impedance of measurement instruments. In commonly used methods input impedance or admittance of a device under test (DUT is derived from measured value of its reflection coefficient causing serious accuracy problems for very high and very low impedances due to insufficient sensitivity of the reflection coefficient to impedance of the DUT. This paper brings theoretical description and experimental verification of a method developed especially for measurement of extreme impedances. The method can significantly improve measurement sensitivity and reduce errors caused by the VNA. It is based on subtraction (or addition of a reference reflection coefficient and the reflection coefficient of the DUT by a passive network, amplifying the resulting signal by an amplifier and measuring the amplified signal as a transmission coefficient by a common vector network analyzer (VNA. A suitable calibration technique is also presented.

Longitudinal coupling impedance of step discontinuities in a circular beam tube

International Nuclear Information System (INIS)

Hahn, H.; Zatz, S.

1979-01-01

The longitudinal coupling impedance presented by a single wall discontinuity to the circulating beam in a circular accelerator or storage ring is usually analyzed by considering a developed periodic structure. However, the typical parameters are often such that it becomes adequate to treat the discontinuity as a nonperiodic problem. Using modal field matching methods, solutions were derived for the cases of a single as well as a double-step discontinuity in a circular beam tube. Numerical results are presented in this paper and the typical behavior at low frequency, at reasonance, and above cut-off is discussed

Degree of coupling in high-rise mixed shear walls structures

Indian Academy of Sciences (India)

A simple method of analysis is presented to determine the influence of single shear walls (SSW) on the degree of coupling DoC and on the peak shear demand PSD for beams of coupled shear walls (CSW) in mixed shear wall structures (MSW). Non-coupled lateral load resisting structures such as singular planar walls and ...

Impedance measurements and simulations for the LHC and HL-LHC injection protection collimator

CERN Document Server

AUTHOR|(CDS)2125995; Biancacci, Nicolò

This thesis focuses on the study and the data analysis of the Injection Protection Collimator (also Injection Protection Target Dump or TDI), one of the Large Hadron Collider (LHC) collimators at CERN, in Geneva. The last chapters also deal with the Segmented TDI (TDIS), the TDI upgrade for High Luminosity-LHC (HL-LHC). Going more into details, measurements on the TDI - hexagonal Boron Nitride (TDI - hBN, installed in the LHC during run 2015) were carried out. Using the obtained results as an input, two derivations followed: one evaluating the layer resistivity and the other one for its thickness, in order to consider all the possible coating degradations that could occur. The whole range of data obtained from both the derivations was then fed to Impedance Wake 2D (IW2D), a code performing numerical simulations, to attain impedances. Finally, the resulting longitudinal impedance was compared to some measurements performed on the real TDIs, immediately after they were removed from the LHC. The TDI - Graphite, ...

Impedance and Collective Effects

CERN Document Server

Metral, E; Rumolo, R; Herr, W

2013-01-01

This document is part of Subvolume C 'Accelerators and Colliders' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Chapter '4 Impedance and Collective Effects' with the content: 4 Impedance and Collective Effects Introduction 4.1 Space Charge 4.2 Wake Fields and Impedances 4.3 Coherent Instabilities 4.4 Landau Damping 4.5 Two-Stream Effects (Electron Cloud and Ions) 4.6 Beam-Beam Effects 4.7 Numerical Modelling

Real-time imaging and detection of intracranial haemorrhage by electrical impedance tomography in a piglet model.

Science.gov (United States)

Xu, C H; Wang, L; Shi, X T; You, F S; Fu, F; Liu, R G; Dai, M; Zhao, Z W; Gao, G D; Dong, X Z

2010-01-01

The aim of this study was to use electrical impedance tomography (EIT) to detect and image acute intracranial haemorrhage (ICH) in an animal model. Blood was infused into the frontal lobe of the brains of anaesthetized piglets and impedance was measured using 16 electrodes placed in a circle on the scalp. The EIT images were constructed using a filtered back-projection algorithm. The mean of all the pixel intensities within a region of interest--the mean resistivity value (MRV)--was used to evaluate the relative impedance changes in the target region. A symmetrical index (SI), reflecting the relative impedance on both sides of the brain, was also calculated. Changes in MRV and SI were associated with the injection of blood, demonstrating that EIT can successfully detect ICH in this animal model. The unique features of EIT may be beneficial for diagnosing ICH early in patients after cranial surgery, thereby reducing the risk of complications and mortality.

Fast Reactive Power Sharing, Circulating Current and Resonance Suppression for Parallel Inverters Using Resistive-Capacitive Output Impedance

DEFF Research Database (Denmark)

Chen, Yandong; Guerrero, Josep M.; Shuai, Zhikang

2016-01-01

In this paper, an inverter using resistivecapacitive output impedance (RC-type inverter) is proposed not only to provide fast reactive power sharing to support microgrid voltage, and but also to reduce circulating currents and damp high-frequency resonances among inverters. Introducing the RC......-frequency resonances among parallel inverters are quantitatively analyzed. The control parameters are systematically selected, and effect of virtual complex impedance on the inverter output voltage is depicted. The RC-type inverter can reduce circulating currents and damp resonances due to different equivalent output...

Soil-structure Interaction in the Seismic Response of Coupled Wall-frame Structures on Pile Foundations

International Nuclear Information System (INIS)

Carbonari, S.; Dezi, F.; Leoni, G.

2008-01-01

This paper presents a study on the seismic response of coupled wall-frame structures founded on piles. A complete soil-structure interaction analysis is carried out with reference to a case study. Three different soils and seven real accelerograms are considered. Local site response analyses are performed in order to evaluate the incoming free-field motion at different depths and the ground motion amplifications. A numerical model, accounting for the pile-soil-pile interaction and for material and radiation damping, is used to evaluate the impedance matrix and the foundation input motion. The domain decomposition technique is adopted to perform time-domain seismic analyses introducing Lumped Parameter Models to take into account the impedance of the soil-structure system. Applications show that the rocking phenomena affect the behaviour of the structure by changing the base shear distribution within the wall and the frame and by increasing the structural displacements

Mechanism transition of cell-impedance-controlled lithium transport through Li1-δMn2O4 composite electrode caused by surface-modification and temperature variation

International Nuclear Information System (INIS)

Jung, Kyu-Nam; Pyun, Su-Il

2007-01-01

The mechanism transition of lithium transport through a Li 1-δ Mn 2 O 4 composite electrode caused by the surface-modification and temperature variation was investigated using the galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and the potentiostatic current transient technique. From the analyses of the ac-impedance spectra, experimentally measured from unmodified Li 1-δ Mn 2 O 4 and surface-modified Li 1-δ Mn 2 O 4 with MgO composite electrodes, the internal cell resistance of the MgO-modified Li 1-δ Mn 2 O 4 electrode was determined to be much smaller in value than that of the unmodified electrode over the whole potential range. Moreover, from the analysis of the anodic current transients measured on the MgO-modified Li 1-δ Mn 2 O 4 electrode, it was found that the cell-impedance-controlled constraint at the electrode surface is changed to a diffusion-controlled constraint, which is characterised by a large potential step and simultaneously by a small amount of lithium transferred during lithium transport. This strongly suggests that the internal cell resistance plays a significant role in determining the cell-impedance-controlled lithium transport through the MgO-modified Li 1-δ Mn 2 O 4 electrode. Furthermore, from the temperature dependence of the internal cell resistance and diffusion resistance in the unmodified Li 1-δ Mn 2 O 4 composite electrode measured by GITT and EIS, it was concluded that which mechanism of lithium transport will be operative strongly depends on the diffusion resistance as well as on the internal cell resistance

The measurement of water transport in porous materials using impedance spectroscopy

International Nuclear Information System (INIS)

Ball, R J; Allen, G C

2010-01-01

This paper describes the application of electrical measurements to monitor the extraction (movement of water from the mortar) of water from calcium lime, natural hydraulic lime and Portland cement mortars placed on an adsorbent brick substrate. Impedance measurements were used to identify the changes in bulk resistance of the mortar. A model has been developed combining sharp front theory and Boltzmann's distribution law of statistical thermodynamics to identify the point at which no further absorption of water into the brick occurs. A linear relationship was found between the exponential of bulk resistance and the square root of time during dewatering. A change in gradient was attributed to the end of dewatering.

Resistive wall modes in the EXTRAP T2R reversed-field pinch

Science.gov (United States)

Brunsell, P. R.; Malmberg, J.-A.; Yadikin, D.; Cecconello, M.

2003-10-01

Resistive wall modes (RWM) in the reversed field pinch are studied and a detailed comparison of experimental growth rates and linear magnetohydrodynamic (MHD) theory is made. RWM growth rates are experimentally measured in the thin shell device EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Controlled Fusion 43, 1 (2001)]. Linear MHD calculations of RWM growth rates are based on experimental equilibria. Experimental and linear MHD RWM growth rate dependency on the equilibrium profiles is investigated experimentally by varying the pinch parameter Θ=Bθ(a)/ in the range Θ=1.5-1.8. Quantitative agreement between experimental and linear MHD growth rates is seen. The dominating RWMs are the internal on-axis modes (having the same helicity as the central equilibrium field). At high Θ, external nonresonant modes are also observed. For internal modes experimental growth rates decrease with Θ while for external modes, growth rates increase with Θ. The effect of RWMs on the reversed-field pinch plasma performance is discussed.

Yeast cell wall extract induces disease resistance against bacterial and fungal pathogens in Arabidopsis thaliana and Brassica crop.

Directory of Open Access Journals (Sweden)

Mari Narusaka

Full Text Available Housaku Monogatari (HM is a plant activator prepared from a yeast cell wall extract. We examined the efficacy of HM application and observed that HM treatment increased the resistance of Arabidopsis thaliana and Brassica rapa leaves to bacterial and fungal infections. HM reduced the severity of bacterial leaf spot and anthracnose on A. thaliana and Brassica crop leaves with protective effects. In addition, gene expression analysis of A. thaliana plants after treatment with HM indicated increased expression of several plant defense-related genes. HM treatment appears to induce early activation of jasmonate/ethylene and late activation of salicylic acid (SA pathways. Analysis using signaling mutants revealed that HM required SA accumulation and SA signaling to facilitate resistance to the bacterial pathogen Pseudomonas syringae pv. maculicola and the fungal pathogen Colletotrichum higginsianum. In addition, HM-induced resistance conferred chitin-independent disease resistance to bacterial pathogens in A. thaliana. These results suggest that HM contains multiple microbe-associated molecular patterns that activate defense responses in plants. These findings suggest that the application of HM is a useful tool that may facilitate new disease control methods.

Impedance source power electronic converters

CERN Document Server

Liu, Yushan; Ge, Baoming; Blaabjerg, Frede; Ellabban, Omar; Loh, Poh Chiang

2016-01-01

Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key features: Comprehensive analysis of the impedance source converter/inverter topologies, including typical topologies and derived topologies. Fully explains the design and control techniques of impedance source converters/inverters, including hardware design and control parameter design for corresponding control methods. Presents the latest power conversion solutions that aim to advance the role of pow...

Online tuning of impedance matching circuit for long pulse inductively coupled plasma source operation—An alternate approach

International Nuclear Information System (INIS)

Sudhir, Dass; Bandyopadhyay, M.; Chakraborty, A.; Kraus, W.; Gahlaut, A.; Bansal, G.

2014-01-01

Impedance matching circuit between radio frequency (RF) generator and the plasma load, placed between them, determines the RF power transfer from RF generator to the plasma load. The impedance of plasma load depends on the plasma parameters through skin depth and plasma conductivity or resistivity. Therefore, for long pulse operation of inductively coupled plasmas, particularly for high power (∼100 kW or more) where plasma load condition may vary due to different reasons (e.g., pressure, power, and thermal), online tuning of impedance matching circuit is necessary through feedback. In fusion grade ion source operation, such online methodology through feedback is not present but offline remote tuning by adjusting the matching circuit capacitors and tuning the driving frequency of the RF generator between the ion source operation pulses is envisaged. The present model is an approach for remote impedance tuning methodology for long pulse operation and corresponding online impedance matching algorithm based on RF coil antenna current measurement or coil antenna calorimetric measurement may be useful in this regard

Hybrid-Source Impedance Networks

DEFF Research Database (Denmark)

Li, Ding; Gao, Feng; Loh, Poh Chiang

2010-01-01

Hybrid-source impedance networks have attracted attention among researchers because of their flexibility in performing buck-boost energy conversion. To date, three distinct types of impedance networks can be summarized for implementing voltage-type inverters with another three types summarized...... for current-type inverters. These impedance networks can in principle be combined into two generic network entities, before multiple of them can further be connected together by applying any of the two proposed generalized cascading concepts. The resulting two-level and three-level inverters implemented using...

Quantized impedance dealing with the damping behavior of the one-dimensional oscillator

Energy Technology Data Exchange (ETDEWEB)

Zhu, Jinghao; Zhang, Jing; Li, Yuan; Zhang, Yong; Fang, Zhengji; Zhao, Peide, E-mail: pdzhao@eyou.com, E-mail: pdzhao@hebut.edu.cn [School of Science, Hebei University of Technology, Beichen Campus, Tianjin 300401 (China); Li, Erping, E-mail: liep@zju.edu.cn [Institute of High Performance Computing, Fusionopolis, 1 Fusionopolis Way, No. 16-16 Connexis, Singapore 138632 (Singapore)

2015-11-15

A quantized impedance is proposed to theoretically establish the relationship between the atomic eigenfrequency and the intrinsic frequency of the one-dimensional oscillator in this paper. The classical oscillator is modified by the idea that the electron transition is treated as a charge-discharge process of a suggested capacitor with the capacitive energy equal to the energy level difference of the jumping electron. The quantized capacitance of the impedance interacting with the jumping electron can lead the resonant frequency of the oscillator to the same as the atomic eigenfrequency. The quantized resistance reflects that the damping coefficient of the oscillator is the mean collision frequency of the transition electron. In addition, the first and third order electric susceptibilities based on the oscillator are accordingly quantized. Our simulation of the hydrogen atom emission spectrum based on the proposed method agrees well with the experimental one. Our results exhibits that the one-dimensional oscillator with the quantized impedance may become useful in the estimations of the refractive index and one- or multi-photon absorption coefficients of some nonmagnetic media composed of hydrogen-like atoms.

Domain Wall Formation in Ferromagnetic Layers: An Ab Initio Study

Science.gov (United States)

Herper, Heike C.

Domain walls are an inherent feature of ferromagnetic (FM) films consisting of layers with different magnetic orientations. Since FM films are used in electrical devices the question of the influence of domain walls on, e.g., the magnetoresistance has attracted much interest. Besides discussing the resistance contribution of domain walls, it is appropriate to study different types of domain walls and their energy of formation. The behaviour of domain walls is usually discussed within model calculations. In the present paper it is done within an ab initio Green's function technique for layered systems, i.e., the fully relativistic, spin-polarized screened Korringa-Kohn Rostoker method. Results are presented for fcc Co layers covered by two semi-infinite fcc Pt(001) bulk systems or by bulk fcc Co(001), respectively. The resistance, which is caused by the different types of domain walls is discussed within a Kubo-Greenwood approach considering Co(001)/Co24/Co(001) as an example.

Roles of tRNA in cell wall biosynthesis

DEFF Research Database (Denmark)

Dare, Kiley; Ibba, Michael

2012-01-01

Recent research into various aspects of bacterial metabolism such as cell wall and antibiotic synthesis, degradation pathways, cellular stress, and amino acid biosynthesis has elucidated roles of aminoacyl-transfer ribonucleic acid (aa-tRNA) outside of translation. Although the two enzyme families...... responsible for cell wall modifications, aminoacyl-phosphatidylglycerol synthases (aaPGSs) and Fem, were discovered some time ago, they have recently become of intense interest for their roles in the antimicrobial resistance of pathogenic microorganisms. The addition of positively charged amino acids...... and play a role in resistance to antibiotics that target the cell wall. Additionally, the formation of truncated peptides results in shorter peptide bridges and loss of branched linkages which makes bacteria more susceptible to antimicrobials. A greater understanding of the structure and substrate...

Study on Shear Performance of Cold-formed Steel Composite Wall with New Type of stud

Science.gov (United States)

Wang, Chungang; Yue, Sizhe; Liu, Hong; Zhang, Zhuangnan

2018-03-01

The shear resistance of single oriented-strand board wall and single gypsum board wall can be improved in different degrees by increasing strength of steel. The experimental data of literatures were used, and the test specimens had been simulated and validated by ABAQUS finite element analysis. According to the research, it showed that the compressive bearing capacity of the new stud composite wall was much better than the common stud composite wall, so the establishment and research of all models had been based on the new section stud. The analysis results show that when using new type of stud the shear resistance of the single oriented-strand board wall can be improved efficiently by increasing strength of steel, but the shear resistance of the single gypsum wall can be increased little.

Subharmonic frequency locking in the resistive Josephson thermometer

International Nuclear Information System (INIS)

van Veldhuizen, M.; Fowler, H.A.

1985-01-01

Phase-locked oscillatory solutions are examined as a basis for the dc impedance of the resistive superconducting quantum-interference device Josephson thermometer. The calculations are based on the resistively shunted junction model in the limit 2πL/sub s/I/sub c//Phi 0 > or =1, where L/sub s/ is the loop inductance and I/sub c/ is the junction critical current, and for a junction resistance large compared with the external shunt resistance. An algorithm for representing frequency entrainment in (kappa,ω) space (drive amplitude, frequency) leads to zones with rotation number p/q having the form of leaf-shaped regions joined and overlapping at their tips. High-resonance zones are very thin and locally similar. No chaotic behavior has been observed. The model can simulate the ''rising'' curves of dc impedance as a function of drive amplitude

Pumping slots: impedances and power losses

Energy Technology Data Exchange (ETDEWEB)

Kurennoy, S [Maryland Univ., College Park, MD (United States). Dept. of Physics

1996-08-01

Contributions of pumping slots to the beam coupling impedances and power losses in a B-factory ring are considered. While their leading contribution is to the inductive impedance, for high-intensity machines with short bunches like e{sup +}e{sup -} B-factories the real part of the impedance and related loss factors are also important. Using an analytical approach we calculate the coupling impedances and loss factors due to slots in a ring with an arbitrary cross section of the vacuum chamber. Effects of the slot tilt on the beam impedance are also considered, and restrictions on the tilt angle are derived from limitations on the impedance increase. The power leakage through the slots is discussed briefly. The results are applied to the KEK B-factory. (author)

Enhancing phonon flow through one-dimensional interfaces by impedance matching

Science.gov (United States)

Polanco, Carlos A.; Ghosh, Avik W.

2014-08-01

We extend concepts from microwave engineering to thermal interfaces and explore the principles of impedance matching in 1D. The extension is based on the generalization of acoustic impedance to nonlinear dispersions using the contact broadening matrix Γ(ω), extracted from the phonon self energy. For a single junction, we find that for coherent and incoherent phonons, the optimal thermal conductance occurs when the matching Γ(ω) equals the Geometric Mean of the contact broadenings. This criterion favors the transmission of both low and high frequency phonons by requiring that (1) the low frequency acoustic impedance of the junction matches that of the two contacts by minimizing the sum of interfacial resistances and (2) the cut-off frequency is near the minimum of the two contacts, thereby reducing the spillage of the states into the tunneling regime. For an ultimately scaled single atom/spring junction, the matching criterion transforms to the arithmetic mean for mass and the harmonic mean for spring constant. The matching can be further improved using a composite graded junction with an exponential varying broadening that functions like a broadband antireflection coating. There is, however, a trade off as the increased length of the interface brings in additional intrinsic sources of scattering.

Dielectric relaxation and ac conduction in γ-irradiated UHMWPE/MWCNTs nano composites: Impedance spectroscopy analysis

International Nuclear Information System (INIS)

Maqbool, Syed Asad; Mehmood, Malik Sajjad; Mukhtar, Saqlain Saqib; Baluch, Mansoor A.; Khan, Shamim; Yasin, Tariq; Khan, Yaqoob

2017-01-01

The dielectric behavior of γ-irradiated ultra-high molecular weight polyethylene (UHMWPE) and its nano composites (NCs) with γ-ray modified multi wall carbon nano tubes (γ-MWCNTs) and MWCNTs had been studied using impedance spectroscopy. The study had been carried out in the frequency range of 20–2 MHz at room temperature. All samples (pure and NCs) were prepared in the form of sheets and irradiated with γ-dose of 50 kGy and 100 kGy, respectively. The comprehensive analysis of results revealed that resistivity of UHMWPE for conduction decreased on irradiation and incorporation of MWCNTs (whether γ ray modified or un-modified) due to the radiation induced damage and conductive networks induced by MWCNTs. At low frequency range a significant increase in the dielectric constant had been observed because of irradiation and addition of MWNCTs. The trend of loss tangent and ac conductivity for each investigated sample depended on resistivity offered and had a decreasing trend as a function of frequency. Moreover, dissipation factor increased with the incorporation of MWNCTs and irradiation from 0.12 to 0.22. In addition to this, non-frequency dependent static dielectric constant was also found to increase with irradiation and incorporation of MWCNTs. The relaxation time was found to increase from 1.2 to 4.3 ms due to hindrance offered by radiation induced mutual cross linking of PE chains and polymer-MWNCTs bindings. - Highlights: • The resistivity for conduction in pristine UHMWPE is decreased with γ-irradiation. • Conduction in PE/MWCNTs nanocomposites increased due to MWCNTs addition. • Static dielectric constant of UHMWPE increased with γ-irradiation. • Static dielectric constant of UHMWPE increased due to MWCNTs incorporation.

Electrical transport properties of CoMn0.2−xGaxFe1.8O4 ferrites using complex impedance spectroscopy

Directory of Open Access Journals (Sweden)

Chien-Yie Tsay

2016-05-01

Full Text Available In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2−xGaxFe1.8O4 (x=0, 0.1, and 0.2 prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z’ and the imaginary part (Z” of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.

Implementation of model predictive control for resistive wall mode stabilization on EXTRAP T2R

Science.gov (United States)

Setiadi, A. C.; Brunsell, P. R.; Frassinetti, L.

2015-10-01

A model predictive control (MPC) method for stabilization of the resistive wall mode (RWM) in the EXTRAP T2R reversed-field pinch is presented. The system identification technique is used to obtain a linearized empirical model of EXTRAP T2R. MPC employs the model for prediction and computes optimal control inputs that satisfy performance criterion. The use of a linearized form of the model allows for compact formulation of MPC, implemented on a millisecond timescale, that can be used for real-time control. The design allows the user to arbitrarily suppress any selected Fourier mode. The experimental results from EXTRAP T2R show that the designed and implemented MPC successfully stabilizes the RWM.

Implementation of model predictive control for resistive wall mode stabilization on EXTRAP T2R

International Nuclear Information System (INIS)

Setiadi, A C; Brunsell, P R; Frassinetti, L

2015-01-01

A model predictive control (MPC) method for stabilization of the resistive wall mode (RWM) in the EXTRAP T2R reversed-field pinch is presented. The system identification technique is used to obtain a linearized empirical model of EXTRAP T2R. MPC employs the model for prediction and computes optimal control inputs that satisfy performance criterion. The use of a linearized form of the model allows for compact formulation of MPC, implemented on a millisecond timescale, that can be used for real-time control. The design allows the user to arbitrarily suppress any selected Fourier mode. The experimental results from EXTRAP T2R show that the designed and implemented MPC successfully stabilizes the RWM. (paper)

Resistance and Resistant Reaction of Gossypium arboreum to the Reniform, Nematode, Rotylenchulus reniformis

Science.gov (United States)

Carter, William W.

1981-01-01

Gossypium arboreum 'Nanking CB 1402' possessed a high level of resistance to Rotylenchulus reniformis. Within 16 h, the nematode penetrated roots of resistant and susceptible cottons equally. After 36 h, significantly fewer nematodes were found in resistant roots. Larvae fed in either an endodermal or pericyclic cell and had no specificity for root tissue of a particular age. In roots of resistant G. arboreum '1402,' wall breakdown of pericyclic cells was evident after 3 d, endodermal and cortical cells collapsed, and the hypertrophied pericyclic cells disintegrated within 12 d. Cell walls immediately adjacent to the nematode's head were thickened and more safranin positive in resistant than in susceptible cotton cultivars. Several other cultivars of G. arboreum were also resistant to R. reniformis, based on nematode fecundity and percent egg reduction. PMID:19300777

Correlation between zirconium oxide impedance and corrosion behavior of Zr-Nb-Sn-Fe-Cu alloys

International Nuclear Information System (INIS)

Park, Sang Yoon; Lee, Myung Ho; Choi, Byoung Kwon; Jeong, Yong Hwan; Jung, Youn Ho

2001-01-01

To evaluate the correlation of Zr oxide impedance and corrosion behavior of Zr-Nb-Sn-Fe-Cu alloys, the corrosion behavior of the alloys was tested in the autoclave containing 70 ppm LiOH solution at 360 .deg. C. The characteristics of the oxide on the alloys were investigated by using the electrochemical impedance spectrosocpy (EIS) method. The corrosion resistance of the alloys was evaluated from the corrosion rate determined as a function of the concentration of Nb. The equivalent circuit of the oxide was composed on the base of the spectrum from EIS measurements on the oxide layers that had formed at pre-and post-transition regions on the curve of corrosion rate. By using the capacitance characteristics of the equivalent circuit, the thickness of impervious layer, it's electrical resistance and characteristics of space charge layer were evaluated. The corrosion characteristics of the Zr-Nb-Sn-Fe-Cu alloys were successfully explained by applying the EIS test results

Magnetoresistance of non-180° domain wall in the presence of electron-photon interaction

Science.gov (United States)

Majidi, Roya

2013-04-01

In the present paper, influence of photon on resistance of non-180° domain wall in metallic magnetic nanowires has been studied using the semiclassical approach. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. The one-dimensional Néel-type domain wall between two ferromagnetic domains with relative magnetization angle less than 180° is considered. By increasing this angle, the contribution of the domain wall in the resistivity of the nanowire becomes considerable. It is also found that the fundamental contribution of the domain wall in resistivity can be controlled by propagating photon. These results are valuable in designing spintronic devices based on magnetic nanowires.

Measurement of bio-impedance with a smart needle to confirm percutaneous kidney access.

Science.gov (United States)

Hernandez, D J; Sinkov, V A; Roberts, W W; Allaf, M E; Patriciu, A; Jarrett, T W; Kavoussi, L R; Stoianovici, D

2001-10-01

The traditional method of percutaneous renal access requires freehand needle placement guided by C-arm fluoroscopy, ultrasonography, or computerized tomography. This approach provides limited objective means for verifying successful access. We developed an impedance based percutaneous Smart Needle system and successfully used it to confirm collecting system access in ex vivo porcine kidneys. The Smart Needle consists of a modified 18 gauge percutaneous access needle with the inner stylet electrically insulated from the outer sheath. Impedance is measured between the exposed stylet tip and sheath using Model 4275 LCR meter (Hewlett-Packard, Sunnyvale, California). An ex vivo porcine kidney was distended by continuous gravity infusion of 100 cm. water saline from a catheter passed through the parenchyma into the collecting system. The Smart Needle was gradually inserted into the kidney to measure depth precisely using a robotic needle placement system, while impedance was measured continuously. The Smart Needle was inserted 4 times in each of 4 kidneys. When the needle penetrated the distended collecting system in 11 of 16 attempts, a characteristic sharp drop in resistivity was noted from 1.9 to 1.1 ohm m. Entry into the collecting system was confirmed by removing the stylet and observing fluid flow from the sheath. This characteristic impedance change was observed only at successful entry into the collecting system. A characteristic sharp drop in impedance signifies successful entry into the collecting system. The Smart Needle system may prove useful for percutaneous kidney access.

Space charge and beam stability issues of the Fermilab proton driver in Phase I

Energy Technology Data Exchange (ETDEWEB)

K. Y. Ng

2001-08-24

Issues concerning beam stability of the proposed Fermilab Proton Driver are studied in its Phase I. Although the betatron tune shifts are dominated by space charge, these shifts are less than 0.25 and will therefore not drive the symmetric and antisymmetric modes of the beam envelope into instability. The longitudinal space charge force is large and inductive inserts may be needed to compensate for the distortion of the rf potential. Although the longitudinal impedance is space charge dominated, it will not drive any microwave instability, unless the real part of the impedance coming from the inductive inserts and wall resistivity of the beam tube are large enough. The design of the beam tube is therefore very important in order to limit the flow of eddy current and keep wall resistivity low. The transverse impedance is also space charge dominated. With the Proton Driver operated at an imaginary transition gamma, however, Landau damping will never be canceled and beam stability can be maintained with negative chromaticities.

Dynamic impedance model of the skin-electrode interface for transcutaneous electrical stimulation.

Directory of Open Access Journals (Sweden)

José Luis Vargas Luna

Full Text Available Transcutaneous electrical stimulation can depolarize nerve or muscle cells applying impulses through electrodes attached on the skin. For these applications, the electrode-skin impedance is an important factor which influences effectiveness. Various models describe the interface using constant or current-depending resistive-capacitive equivalent circuit. Here, we develop a dynamic impedance model valid for a wide range stimulation intensities. The model considers electroporation and charge-dependent effects to describe the impedance variation, which allows to describe high-charge pulses. The parameters were adjusted based on rectangular, biphasic stimulation pulses generated by a stimulator, providing optionally current or voltage-controlled impulses, and applied through electrodes of different sizes. Both control methods deliver a different electrical field to the tissue, which is constant throughout the impulse duration for current-controlled mode or have a very current peak for voltage-controlled. The results show a predominant dependence in the current intensity in the case of both stimulation techniques that allows to keep a simple model. A verification simulation using the proposed dynamic model shows coefficient of determination of around 0.99 in both stimulation types. The presented method for fitting electrode-skin impedance can be simple extended to other stimulation waveforms and electrode configuration. Therefore, it can be embedded in optimization algorithms for designing electrical stimulation applications even for pulses with high charges and high current spikes.

Short-circuit impedance measurement

DEFF Research Database (Denmark)

Pedersen, Knud Ole Helgesen; Nielsen, Arne Hejde; Poulsen, Niels Kjølstad

2003-01-01

Methods for estimating the short-circuit impedance in the power grid are investigated for various voltage levels and situations. The short-circuit impedance is measured, preferably from naturally occurring load changes in the grid, and it is shown that such a measurement system faces different...

Faraday cup with nanosecond response and adjustable impedance for fast electron beam characterization

International Nuclear Information System (INIS)

Hu Jing; Rovey, Joshua L.

2011-01-01

A movable Faraday cup design with simple structure and adjustable impedance is described in this work. This Faraday cup has external adjustable shunt resistance for self-biased measurement setup and 50 Ω characteristic impedance to match with 50 Ω standard BNC coaxial cable and vacuum feedthroughs for nanosecond-level pulse signal measurements. Adjustable shunt resistance allows self-biased measurements to be quickly acquired to determine the electron energy distribution function. The performance of the Faraday cup is validated by tests of response time and amplitude of output signal. When compared with a reference source, the percent difference of the Faraday cup signal fall time is less than 10% for fall times greater than 10 ns. The percent difference of the Faraday cup signal pulse width is below 6.7% for pulse widths greater than 10 ns. A pseudospark-generated electron beam is used to compare the amplitude of the Faraday cup signal with a calibrated F-70 commercial current transformer. The error of the Faraday cup output amplitude is below 10% for the 4-14 kV tested pseudospark voltages. The main benefit of this Faraday cup is demonstrated by adjusting the external shunt resistance and performing the self-biased method for obtaining the electron energy distribution function. Results from a 4 kV pseudospark discharge indicate a ''double-humped'' energy distribution.

Faraday cup with nanosecond response and adjustable impedance for fast electron beam characterization.

Science.gov (United States)

Hu, Jing; Rovey, Joshua L

2011-07-01

A movable Faraday cup design with simple structure and adjustable impedance is described in this work. This Faraday cup has external adjustable shunt resistance for self-biased measurement setup and 50 Ω characteristic impedance to match with 50 Ω standard BNC coaxial cable and vacuum feedthroughs for nanosecond-level pulse signal measurements. Adjustable shunt resistance allows self-biased measurements to be quickly acquired to determine the electron energy distribution function. The performance of the Faraday cup is validated by tests of response time and amplitude of output signal. When compared with a reference source, the percent difference of the Faraday cup signal fall time is less than 10% for fall times greater than 10 ns. The percent difference of the Faraday cup signal pulse width is below 6.7% for pulse widths greater than 10 ns. A pseudospark-generated electron beam is used to compare the amplitude of the Faraday cup signal with a calibrated F-70 commercial current transformer. The error of the Faraday cup output amplitude is below 10% for the 4-14 kV tested pseudospark voltages. The main benefit of this Faraday cup is demonstrated by adjusting the external shunt resistance and performing the self-biased method for obtaining the electron energy distribution function. Results from a 4 kV pseudospark discharge indicate a "double-humped" energy distribution.

Characterization and evaluation of Pt-Ru catalyst supported on multi-walled carbon nanotubes by electrochemical impedance

Energy Technology Data Exchange (ETDEWEB)

Ocampo, A.L.; Miranda-Hernandez, M.; Sebastian, P.J. [Centro de Investigacion en Energia-UNAM, Temixco, 62580 Morelos (Mexico); Morgado, J.; Montoya, J.A. [IMP, Eje Central Lazaro Cardenas 152, 07730 D.F. Mexico (Mexico)

2006-10-06

In this work the authors present the results of a systematic characterization and evaluation of the carbon nanotube supported Pt-Ru (Pt-Ru/CNT) for its use as methanol oxidation catalyst. Its activity was compared with that of Pt and Pt-Ru catalysts supported on Vulcan and synthesized from carbonyl precursors, and another commercial Pt-Ru catalyst. The cyclic voltammetry, CO stripping and electrochemical impedance techniques were employed to determine the electrocatalytic activity of the catalysts. The electrochemical studies were performed in 0.5M H{sub 2}SO{sub 4} containing different concentrations of methanol (0.05-1M). The results showed a noticeable influence of the catalyst support (CNT) on the performance of the catalyst for CO oxidation. The electrochemical impedance studies allowed us to separate the different steps in the methanol oxidation reaction and to control these steps or reactions by varying the applied potential and the methanol concentration. At low methanol concentration and potentials the de-hydrogenation of methanol predominated. But, at high potential and methanol concentrations, the CO oxidation predominated. These results allowed us to clearly describe at what potential and concentration ranges the bi-functional effect of Ru becomes evident. Our results indicated that the CO oxidation occurs both on Pt and Ru. Compared to other catalysts, Pt-Ru supported on carbon nanotubes showed superior catalytic activity for CO and methanol oxidation. (author)

Direct correlation between potentiometric and impedance biosensing of antibody-antigen interactions using an integrated system

Science.gov (United States)

Tsai, Meng-Yen; Creedon, Niamh; Brightbill, Eleanor; Pavlidis, Spyridon; Brown, Billyde; Gray, Darren W.; Shields, Niall; Sayers, Ríona; Mooney, Mark H.; O'Riordan, Alan; Vogel, Eric M.

2017-08-01

A fully integrated system that combines extended gate field-effect transistor (EGFET)-based potentiometric biosensors and electrochemical impedance spectroscopy (EIS)-based biosensors has been demonstrated. This integrated configuration enables the sequential measurement of the same immunological binding event on the same sensing surface and consequently sheds light on the fundamental origins of sensing signals produced by FET and EIS biosensors, as well as the correlation between the two. Detection of both the bovine serum albumin (BSA)/anti-BSA model system in buffer solution and bovine parainfluenza antibodies in complex blood plasma samples was demonstrated using the integrated biosensors. Comparison of the EGFET and EIS sensor responses reveals similar dynamic ranges, while equivalent circuit modeling of the EIS response shows that the commonly reported total impedance change (ΔZtotal) is dominated by the change in charge transfer resistance (Rct) rather than surface capacitance (Csurface). Using electrochemical kinetics and the Butler-Volmer equation, we unveil that the surface potential and charge transfer resistance, measured by potentiometric and impedance biosensors, respectively, are, in fact, intrinsically linked. This observation suggests that there is no significant gain in using the FET/EIS integrated system and leads to the demonstration that low-cost EGFET biosensors are sufficient as a detection tool to resolve the charge information of biomolecules for practical sensing applications.

Application of bioelectrical impedance analysis in prediction of light kid carcass and muscle chemical composition.

Science.gov (United States)

Silva, S R; Afonso, J; Monteiro, A; Morais, R; Cabo, A; Batista, A C; Guedes, C M; Teixeira, A

2018-06-01

Carcass data were collected from 24 kids (average live weight of 12.5±5.5 kg; range 4.5 to 22.4 kg) of Jarmelista Portuguese native breed, to evaluate bioelectrical impedance analysis (BIA) as a technique for prediction of light kid carcass and muscle chemical composition. Resistance (Rs, Ω) and reactance (Xc, Ω), were measured in the cold carcasses with a single frequency bioelectrical impedance analyzer and, together with impedance (Z, Ω), two electrical volume measurements (VolA and VolB, cm2/Ω), carcass cold weight (CCW), carcass compactness and several carcass linear measurements were fitted as independent variables to predict carcass composition by stepwise regression analysis. The amount of variation explained by VolA and VolB only reached a significant level (Pcarcass fat weight (0.814⩽R 2⩽0.862; Pcarcass fat weight (combined with carcass length, CL; R 2=0.943; Pcarcass composition.

Electron transfer behaviour of single-walled carbon nanotubes electro-decorated with nickel and nickel oxide layers

Energy Technology Data Exchange (ETDEWEB)

Adekunle, Abolanle S.; Ozoemena, Kenneth I. [Department of Chemistry, University of Pretoria, Pretoria 0002 (South Africa)

2008-08-01

The electron transfer behaviour of nickel film-decorated single-walled carbon nanotubes (SWCNTs-Ni) at edge plane pyrolytic graphite electrodes (EPPGEs) was investigated. The impact of SWCNTs on the redox properties of the nickel film was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). From EIS data, obtained using ferrocyanide/ferricyanide as a redox probe, we show that the electrodes based on nickel and nickel oxide films follow electrical equivalent circuit models typical of partial charge transfer or adsorption-controlled kinetics, resembling the 'electrolyte-insulator-semiconductor sensors (EIS)'. From the models, we prove that EPPGE-SWCNT-Ni exhibits the least resistance to charge transport compared to other electrodes (approximately 30 times faster than the EPPGE-SWCNT-NiO, 25 times faster than EPPGE-SWCNT, and over 300 times faster than the bare EPPGE) suggesting the ability of the SWCNTs to act as efficient conducting species that facilitate electron transport of the integrated nickel and nickel oxide particles. (author)

Electrochemical Impedance Spectroscopy (EIS) Characterization of Reformate-operated High Temperature PEM Fuel Cell Stack

DEFF Research Database (Denmark)

Sahlin, Simon Lennart; Simon Araya, Samuel; Andreasen, Søren Juhl

2017-01-01

their effects on a reformate-operated stack. Polarization curves were also recorded to complement the impedance analysis of the researched phenomena. An equivalent circuit model was used to estimate the different resistances at varying parameters. It showed a significantly higher low frequency resistance......, λanode= 1.6 for reformate operation and λcathode= 4.The work also compared dry hydrogen, steam reforming and autothermal reforming gas feeds at160 ◦Cand showed appreciably lower performance in the case of autothermal reforming at the same stoichiometry, mainly attributable to mass transport related...

Structure and Mechanism of Staphylococcus aureus TarS, the Wall Teichoic Acid β-glycosyltransferase Involved in Methicillin Resistance.

Directory of Open Access Journals (Sweden)

Solmaz Sobhanifar

2016-12-01

Full Text Available In recent years, there has been a growing interest in teichoic acids as targets for antibiotic drug design against major clinical pathogens such as Staphylococcus aureus, reflecting the disquieting increase in antibiotic resistance and the historical success of bacterial cell wall components as drug targets. It is now becoming clear that β-O-GlcNAcylation of S. aureus wall teichoic acids plays a major role in both pathogenicity and antibiotic resistance. Here we present the first structure of S. aureus TarS, the enzyme responsible for polyribitol phosphate β-O-GlcNAcylation. Using a divide and conquer strategy, we obtained crystal structures of various TarS constructs, mapping high resolution overlapping N-terminal and C-terminal structures onto a lower resolution full-length structure that resulted in a high resolution view of the entire enzyme. Using the N-terminal structure that encapsulates the catalytic domain, we furthermore captured several snapshots of TarS, including the native structure, the UDP-GlcNAc donor complex, and the UDP product complex. These structures along with structure-guided mutants allowed us to elucidate various catalytic features and identify key active site residues and catalytic loop rearrangements that provide a valuable platform for anti-MRSA drug design. We furthermore observed for the first time the presence of a trimerization domain composed of stacked carbohydrate binding modules, commonly observed in starch active enzymes, but adapted here for a poly sugar-phosphate glycosyltransferase.

Rf Discharge Impedance Measurements Using a New Method to Determine the Stray Impedances

NARCIS (Netherlands)

Bakker, L.P.; Kroesen, G.M.W.; Hoog, de F.J.

1999-01-01

The impedance of a capacitively coupled radio frequency discharge in a tubular fluorescent lamp filled with neon and mercury is measured. The stray impedances in the electrical network are determined using a new method that requires no extra instruments. The reflection of power is used to determine

Estimation of total body water by bioelectrical impedance analysis

International Nuclear Information System (INIS)

Kushner, R.F.; Schoeller, D.A.

1986-01-01

Total body water (TBW) measured by bioelectrical impedance analysis (BIA) was directly compared with deuterium-isotope dilution in a total of 58 subjects. First, sex-specific and group equations were developed by multiple regression analysis in (10 each) obese and nonobese men and women. Height/resistive impedance was the most significant variable used to predict deuterium-dilution space (D2O-TBW) and, combined with weight, yielded R = 0.99 and SE of estimate = 1.75 L. Equations predicted D2O-TBW equally well for obese and nonobese subjects. Second, the equations were prospectively tested in a heterogeneous group of 6 males and 12 females. Sex-specific equations predicted D2O-TBW with good correlation coefficients (0.96 and 0.93), total error (2.34 and 2.89 L), and a small difference between mean predicted and measured D2O-TBW (-1.4 +/- 2.05 and -0.48 +/- 2.83 L). BIA predicts D2O-TBW more accurately than weight, height, and/or age. A larger population is required to validate the applicability of our equations

Impedance of a nanoantenna

International Nuclear Information System (INIS)

Greffet, Jean-Jacques; Laroche, Marine; Marquier, Francois

2009-01-01

We introduce a generalized definition of the impedance of a nanoantenna that can be applied to any system. We also introduce a definition of the impedance of a two level system. Using this framework, we establish a link between the electrical engineering and the quantum optics picture of light emission.

Frequency dependence of the active impedance component of silicon thin-film resistors

International Nuclear Information System (INIS)

Belogurov, S.V.; Gostilo, V.V.; Yurov, A.S.

1987-01-01

A high-resistant resistor on the silicon thin-film substrate considerably superior in noise and frequency performance than commercial resistors is described. The frequency dependence of the active impedance component is tested for determining noise and frequency dependences of silicon thin-film resistors. The obtained results permit to calculate the energy equivalent of resistor noise in nuclear radiation detection units at any temperature according to its frequency characteristic at room temperature

Forced convection heat transfer in rectangular ducts - general case of wall resistances and peripheral conduction for ventilation cooling of nuclear waste repositories [ heat transfer and nuclear disposal

Energy Technology Data Exchange (ETDEWEB)

Lyczkowski, R. W.; Solbrig, C. W.; Gidaspow, D.

1980-01-01

A numerical solution for laminar flow heat transfer between a flowing gas and its containing rectangular duct has been obtained for many different boundary conditions which may arise in nuclear waste repository ventilation corridors. The problem has been solved for the cases of insulation on no walls, one wall, two walls, and three walls with various finite resistances on the remaining walls. Simplifications are made to decouple the convective heat transfer problem for the far field conduction problem, but peripheral conduction is retained. Results have been obtained for several duct aspect ratios in the thermal entrance and in the fully developed regions, including the constant temperature cases. When one wall is insulated and the other three are at constant temperature, the maximum temperature occurs in the fluid rather than on the insulated wall. This maximum moves toward the insulated wall with increasing axial distance. Nusselt numbers for the same constant flux on all four walls with peripheral conduction lie in a narrow band bounded by zero and infinite peripheral conduction cases. A dimensionless wall conduction group of four can be considered infinite for the purpose of estimating fully developed Nusselt numbers to within an accuracy of 3%. A decrease in wall and bulk temperatures by finite wall conduction has been demonstrated for the case of a black body radiation boundary condition. Nusselt numbers for the case of constant temperature on the top and bottom walls and constant heat flux on the side walls exhibited unexpected behavior.

Application of flexi-wall in noise barriers renewal

Directory of Open Access Journals (Sweden)

B. Daee

2015-12-01

Full Text Available This paper presents an experimental study on structural performance of an innovative noise barrier consisting of poly-block, light polyurethane foam (LPF and polyurea. This wall system (flexi-wall is intended to be employed as a vertical extension to existing noise barriers (sound walls in an accelerated construction method. To aid in the wall design, several mechanical tests were conducted on LPF specimens and two full-scale walls were then fabricated employing the same LPF material. The full-scale walls were subjected to lateral loading in order to establish their lateral resistance. A cyclic fatigue test was also performed on a full-scale flexi-wall in order to evaluate the performance of the wall under a repetitive loading condition. The results of the experiments indicated the suitability of flexi-wall in accelerated construction and confirmed that the structural performance of the wall system under lateral loading is satisfactory for the sound wall application. The experimental results were discussed and a preliminary design procedure for application of flexi-wall in sound wall applications was also developed.

Quantized impedance dealing with the damping behavior of the one-dimensional oscillator

Directory of Open Access Journals (Sweden)

Jinghao Zhu

2015-11-01

Full Text Available A quantized impedance is proposed to theoretically establish the relationship between the atomic eigenfrequency and the intrinsic frequency of the one-dimensional oscillator in this paper. The classical oscillator is modified by the idea that the electron transition is treated as a charge-discharge process of a suggested capacitor with the capacitive energy equal to the energy level difference of the jumping electron. The quantized capacitance of the impedance interacting with the jumping electron can lead the resonant frequency of the oscillator to the same as the atomic eigenfrequency. The quantized resistance reflects that the damping coefficient of the oscillator is the mean collision frequency of the transition electron. In addition, the first and third order electric susceptibilities based on the oscillator are accordingly quantized. Our simulation of the hydrogen atom emission spectrum based on the proposed method agrees well with the experimental one. Our results exhibits that the one-dimensional oscillator with the quantized impedance may become useful in the estimations of the refractive index and one- or multi-photon absorption coefficients of some nonmagnetic media composed of hydrogen-like atoms.

Efficiency Investigation of Switch Mode Power Amplifier Drving Low Impedance Transducers

DEFF Research Database (Denmark)

Iversen, Niels Elkjær; Schneider, Henrik; Knott, Arnold

2015-01-01

the amplifier rail voltage requirement as a function of the voice coil nominal resistance is presented. The method is based on a crest factor analysis of music signals and estimation of the electrical power requirement from a specific target of the sound pressure level. Experimental measurements confirms a huge...... performance leap in terms of efficiency compared to a conventional battery driven sound system. Future optimization of low voltage, high current amplifiers for low impedance loudspeaker drivers are discussed....

Cascaded impedance networks for NPC inverter

DEFF Research Database (Denmark)

Li, Ding; Gao, Feng; Loh, Poh Chiang

2010-01-01

they are subject to the renewable sources. To date, three distinct types of impedance networks can be summarized for implementing a hybrid source impedance network, which can in principle be combined and cascaded before connected to a NPC inverter by proposed two ways. The resulting cascaded impedance network NPC...

Studies of longitudinal profile of electron bunches and impedance measurements at Indus-2 synchrotron radiation source

Energy Technology Data Exchange (ETDEWEB)

Garg, Akash Deep, E-mail: akash-deep@rrcat.gov.in [Beam Diagnostics Section (BDS), Indus Operations, Beam Dynamics and Diagnostics Division (IOBDD), Raja Ramanna Centre for Advanced Technology, Indore 452 013, M.P. (India); Homi Bhabha National Institute (HBNI) at Raja Ramanna Centre for Advanced Technology, Indore (India); Yadav, S.; Kumar, Mukesh; Shrivastava, B.B.; Karnewar, A.K.; Ojha, A.; Puntambekar, T.A. [Beam Diagnostics Section (BDS), Indus Operations, Beam Dynamics and Diagnostics Division (IOBDD), Raja Ramanna Centre for Advanced Technology, Indore 452 013, M.P. (India)

2016-04-01

Indus-2 is a 3rd generation synchrotron radiation source at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We study the longitudinal profile of electrons in Indus-2 by using dual sweep synchroscan streak camera at visible diagnostic beamline. In this paper, the longitudinal profiles of electron bunch are analyzed by filling beam current in a single bunch mode. These studies are carried at injection energy (550 MeV) and at ramped beam energy (2.5 GeV). The effects of the wakefield generated interactions between the circulating electrons and the surrounding vacuum chamber are analyzed in terms of measured effects on longitudinal beam distribution. The impedance of the storage ring is obtained by fitting the solutions of Haissinski equation to the measured bunch lengthening with different impedance models. The impedance of storage ring obtained by a series R+L impedance model indicates a resistance (R) of 1350±125 Ω, an inductance (L) of 180±25 nH and broadband impedance of 2.69 Ω. These results are also compared with the values obtained from measured synchronous phase advancing and scaling laws. These studies are very useful in better understanding and control of the electromagnetic interactions.

Sequential interactions of silver-silica nanocomposite (Ag-SiO2 NC) with cell wall, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple antibiotic-resistant bacterium

Digital Repository Service at National Institute of Oceanography (India)

Anas, A.; Jiya, J.; Rameez, M.J.; Anand, P.B.; Anantharaman, M.R.; Nair, S.

The study was carried out to understand the effect of silver–silica nanocomposite (Ag-SiO sub(2)NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drug-resistant bacterium. Bacterial sensitivity...

Sequential interactions of silver-silica nanocomposite (Ag-SiO2NC) with cell wall, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple antibiotic-resistant bacterium

Digital Repository Service at National Institute of Oceanography (India)

Anas, A.; Jiya, J.; Rameez, M.J.; Anand, P.B.; Anantharaman, M.R.; Nair, S.

The study was carried out to understand the effect of silver-silica nanocomposite (Ag-SiO sub(2)NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drug-resistant bacterium Bacterial sensitivity...

Strengthening of Unreinforced Masonry Walls with Composite Materials

Directory of Open Access Journals (Sweden)

Ioana-Sorina Enţuc

2004-01-01

Full Text Available Unreinforced masonry (URM is considered one of the oldest construction materials being until the end of XIXth century, the basic material for: foundations, walls, columns, volts, staircases, floor joints, roofs, retaining walls, drainage channels, barrages, etc. Construction with URM elements posses a series of advantages such as: fire resistance, thermal an acoustic insulations between interior and outside spaces, humidity resistance. However the URM elements have some significant inconveniences such as: large self weight (heaviness causes cracks in the other elements of structures, reduced mechanical strengths in comparison with other traditional materials (steel and concrete, low tenacity, great manual labor consumptions, and vulnerability to earthquakes. Various factors cause deteriorations which must be overcome by strengthening solutions. Some strengthening solutions based on fiber reinforced polymers (FRP products applied directly on URM brick walls are presented in the paper.

Degree of coupling in high-rise mixed shear walls structures

Indian Academy of Sciences (India)

assessment of the structural behaviour of coupled shear wall bents in mixed shear wall ... efficient lateral load resisting system against wind and earthquake effects. .... can be obtained from the second derivative of equation (11) which must be ...

Temporary formation of highly conducting domain walls for non-destructive read-out of ferroelectric domain-wall resistance switching memories

Science.gov (United States)

Jiang, Jun; Bai, Zi Long; Chen, Zhi Hui; He, Long; Zhang, David Wei; Zhang, Qing Hua; Shi, Jin An; Park, Min Hyuk; Scott, James F.; Hwang, Cheol Seong; Jiang, An Quan

2018-01-01

Erasable conductive domain walls in insulating ferroelectric thin films can be used for non-destructive electrical read-out of the polarization states in ferroelectric memories. Still, the domain-wall currents extracted by these devices have not yet reached the intensity and stability required to drive read-out circuits operating at high speeds. This study demonstrated non-destructive read-out of digital data stored using specific domain-wall configurations in epitaxial BiFeO3 thin films formed in mesa-geometry structures. Partially switched domains, which enable the formation of conductive walls during the read operation, spontaneously retract when the read voltage is removed, reducing the accumulation of mobile defects at the domain walls and potentially improving the device stability. Three-terminal memory devices produced 14 nA read currents at an operating voltage of 5 V, and operated up to T = 85 °C. The gap length can also be smaller than the film thickness, allowing the realization of ferroelectric memories with device dimensions far below 100 nm.

Manipulation of near-wall turbulence by surface slip and permeability

Science.gov (United States)

Gómez-de-Segura, G.; Fairhall, C. T.; MacDonald, M.; Chung, D.; García-Mayoral, R.

2018-04-01

We study the effect on near-wall turbulence of tangential slip and wall-normal transpiration, typically produced by textured surfaces and other surface manipulations. For this, we conduct direct numerical simulations (DNSs) with different virtual origins for the different velocity components. The different origins result in a relative wall-normal displacement of the near-wall, quasi-streamwise vortices with respect to the mean flow, which in turn produces a change in drag. The objective of this work is to extend the existing understanding on how these virtual origins affect the flow. In the literature, the virtual origins for the tangential velocities are typically characterised by slip boundary conditions, while the wall-normal velocity is assumed to be zero at the boundary plane. Here we explore different techniques to define and implement the three virtual origins, with special emphasis on the wall-normal one. We investigate impedance conditions relating the wall-normal velocity to the pressure, and linear relations between the velocity components and their wall-normal gradients, as is typically done to impose slip conditions. These models are first tested to represent a smooth wall below the boundary plane, with all virtual origins equal, and later for different tangential and wall-normal origins. Our results confirm that the change in drag is determined by the offset between the origins perceived by mean flow and the quasi-streamwise vortices or, more generally, the near-wall turbulent cycle. The origin for the latter, however, is not set by the spanwise virtual origin alone, as previously proposed, but by a combination of the spanwise and wall-normal origins, and mainly determined by the shallowest of the two. These observations allow us to extend the existing expression to predict the change in drag, accounting for the wall-normal effect when the transpiration is not negligible.

Electrochemical Impedance and Polarization Corrosion Studies of Tantalum Surface Modified by DC Plasma Electrolytic Oxidation

Directory of Open Access Journals (Sweden)

Maciej Sowa

2018-04-01

Full Text Available Tantalum has recently become an actively researched biomaterial for the bone reconstruction applications because of its excellent corrosion resistance and successful clinical records. However, a bare Ta surface is not capable of directly bonding to the bone upon implantation and requires some method of bioactivation. In this study, this was realized by direct current (DC plasma electrolytic oxidation (PEO. Susceptibility to corrosion is a major factor determining the service-life of an implant. Therefore, herein, the corrosion resistance of the PEO coatings on Ta was investigated in Ringer’s solution. The coatings were formed by galvanostatic anodization up to 200, 300 and 400 V, after which the treatment was conducted potentiostatically until the total process time amounted to 5 min. Three solutions containing Ca(H2PO22, Ca(HCOO2 and Mg(CH3COO2 were used in the treatment. For the corrosion characterization, electrochemical impedance spectroscopy and potentiodynamic polarization techniques were chosen. The coatings showed the best corrosion resistance at voltages low enough so that the intensive sparking was absent, which resulted in the formation of thin films. The impedance data were fitted to the equivalent electrical circuits with two time constants, namely R(Q[R(QR] and R(Q[R(Q[RW

Exploring student teachers' resistance to teacher education pedagogies

NARCIS (Netherlands)

Bronkhorst, L.H.; Koster, B.; Meijer, P.C.; Woldman, N.; Vermunt, J.D.

2014-01-01

Student teachers' resistance to teacher education is often understood as a lack of quality of the student teacher and/or the internship, and is expected to impede learning. In this study we suggest that resistance is interactive in nature, and can potentially have constructive outcomes. We engaged

Impedance Mismatch study between the Microwave Generator and the PUPR Plasma Machine

International Nuclear Information System (INIS)

Gaudier, Jorge R.; Castellanos, Ligeia; Encarnacion, Kabir; Zavala, Natyaliz; Rivera, Ramon; Farahat, Nader; Leal, Edberto

2006-01-01

Impedance mismatch inside the connection from the microwave power generator to the plasma machine is studied. A magnetron power generator transmits microwaves of 2.45 GHz and variable power from 50W to 5000W, through a flexible rectangular waveguide to heat plasma inside a Mirror Cusp devise located at the Polytechnic University of Puerto Rico. Before the production of plasma, the residual gas of the devise must be extracted by a vacuum system (5Torr or better), then Argon gas is injected to the machine. The microwaves heat the Argon ions to initiate ionization and plasma is produced. A dielectric wall is used inside the rectangular waveguide to isolate the plasma machine and maintain vacuum. Even though the dielectric will not block the wave propagation, some absorption of microwaves will occur. This absorption will cause reflection, reducing the efficiency of the power transfer. Typically a thin layer of Teflon is used, but measurements using this dielectric show a significant reflection of power back to the generator. Due to the high-power nature of the generator (5KW), this mismatch is not desirable. An electromagnetic field solver based on the Finite Difference Time Domain Method(FDTD) is used to model the rectangular waveguide connection. The characteristic impedance of the simulation is compared with the analytical formula expression and a good agreement is obtain. Furthermore the Teflon-loaded guide is modeled using the above program and the input impedance is computed. The reflection coefficient is calculated based on the transmission line theory with the characteristic and input impedances. Based on the simulation results it is possible to optimize the thickness, shape and dielectric constant of the material, in order to seal the connection with a better match

Application of two electrical methods for the rapid assessment of freezing resistance in Salix epichloro

Energy Technology Data Exchange (ETDEWEB)

Tsarouhas, V.; Kenney, W.A.; Zsuffa, L. [University of Toronto, Ontario (Canada). Faculty of Forestry

2000-09-01

The importance of early selection of frost-resistant Salix clones makes it desirable to select a rapid and accurate screening method for assessing freezing resistance among several genotypes. Two electrical methods, stem electrical impedance to 1 and 10 khz alternating current, and electrolyte leakage of leaf tissue, were evaluated for detecting freezing resistance on three North America Salix epichloro Michx., clones after subjecting them to five different freezing temperatures (-1, -2, -3, -4, and -5 deg C). Differences in the electrical impedance to 1 and 10 kHz, and the ratio of the impedance at the two frequencies (low/high) before and after the freezing treatment (DZ{sub low}, DZ{sub high}, and DZ{sub ratio}, respectively) were estimated. Electrolyte leakage was expressed as relative conductivity (RC{sub t}) and index of injury (IDX{sub t}). Results from the two methods, obtained two days after the freezing stress, showed that both electrical methods were able to detect freezing injury in S. eriocephala. However, the electrolyte leakage method detected injury in more levels of freezing stress (-3, -4, and -5 deg C) than the impedance (-4, and -5 deg C), it assessed clonal differences in S. eriocephala freezing resistance, and it was best suited to correlate electrical methods with the visual assessed freezing injury. No significant impedance or leakage changes were found after the -1 and -2 deg C freezing temperatures. (author)

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

Science.gov (United States)

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

2014-01-01

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

Glucose aided preparation of tungsten sulfide/multi-wall carbon nanotube hybrid and use as counter electrode in dye-sensitized solar cells.

Science.gov (United States)

Wu, Jihuai; Yue, Gentian; Xiao, Yaoming; Huang, Miaoliang; Lin, Jianming; Fan, Leqing; Lan, Zhang; Lin, Jeng-Yu

2012-12-01

The tungsten sulfide/multi-wall carbon nanotube (WS(2)/MWCNT) hybrid was prepared in the presence of glucose by the hydrothermal route. The hybrid materials were used as counter electrode in the dye-sensitized solar cell (DSSC). The results of cyclic voltammetry measurement and electrochemical impedance spectroscopy indicated that the glucose aided prepared (G-A) WS(2)/MWCNT electrode had low charge-transfer resistance (R(ct)) and high electrocatalytic activity for triiodide reduction. The excellent electrochemical properties for (G-A) WS(2)/MWCNT electrode is due to the synergistic effects of WS(2) and MWCNTs, as well as amorphous carbon introduced by glucose. The DSSC based on the G-A WS(2)/MWCNT counter electrode achieved a high power conversion efficiency of 7.36%, which is comparable with the performance of the DSSC using Pt counter electrode (7.54%).

Electrochemical Characterization and Degradation Analysis of Large SOFC Stacks by Impedance Spectroscopy

DEFF Research Database (Denmark)

Mosbæk, Rasmus Rode; Hjelm, Johan; Barfod, R.

2013-01-01

As solid oxide fuel cell (SOFC) technology is moving closer to a commercial break through, lifetime limiting factors, and methods to measure the “state-of-health” of operating cells and stacks are becoming of increasing interest. This requires application of advanced methods for detailed...... electrochemical characterization during operation. An experimental stack with low ohmic resistance from Topsoe Fuel Cell A/S was characterized in detail using electrochemical impedance spectroscopy (EIS). An investigation of the optimal geometrical placement of the current feeds and voltage probes was carried out...... with hydrogen as fuel with 52% fuel utilization and constant current load (0.2 A cm–2) at 750 °C. Stack interconnects were coated with six different coatings to prevent chromium poisoning on the cathode side. Four repeating units (RUs) with different coatings were selected for detailed impedance analysis. EIS...

Tracking of electrochemical impedance of batteries

Science.gov (United States)

Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.

2016-04-01

This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.

RHIC injection kicker impedance

International Nuclear Information System (INIS)

Mane, V.; Peggs, S.; Trbojevic, D.; Zhang, W.

1995-01-01

The longitudinal impedance of the RHIC injection kicker is measured using the wire method up to a frequency of 3 GHz. The mismatch between the 50 ohm cable and the wire and pipe system is calibrated using the TRL calibration algorithm. Various methods of reducing the impedance, such as coated ceramic pipe and copper strips are investigated

Impedance Analysis of the Conditioning of PBI–Based Electrode Membrane Assemblies for High Temperature PEM Fuel Cells

DEFF Research Database (Denmark)

Araya, Samuel Simon; Vang, Jakob Rabjerg; Andreasen, Søren Juhl

2013-01-01

This work analyses the conditioning of single fuel cell assemblies based on different membrane electrode assembly (MEA) types, produced by different methods. The analysis was done by means of electrochemical impedance spectroscopy, and the changes in the fitted resistances of the all the tested...

First wall of thermonuclear device

International Nuclear Information System (INIS)

Kizawa, Makoto; Koizumi, Makoto; Nishihara, Yoshihiro.

1990-01-01

The first wall of a thermonuclear device is constituted with inner wall tiles, e.g. made of graphite and metal substrates for fixing them. However, since the heat expansion coefficient is different between the metal substrates and intermediate metal members, thermal stresses are caused to deteriorate the endurance of the inner wall tiles. In view of the above, low melting metals are disposed at the portion of contact between the inner wall tiles and the metal substrates and, further, a heat pipe structure is incorporated into the metal substrates. Under the thermal load, for example, during operation of the thermonuclear device, the low melting metals at the portion of contact are melted into liquid metals to enhance the state of contact between the inner wall tiles and the metal substrate to reduce the heat resistance and improve the heat conductivity. Even if there is a difference in the heat expansion coefficient between the inner wall tiles and the metal substrates, neither sharing stresses not thermal stresses are caused. Further, since the heat pipe structure is incorporated into the metal substrates, the lateral unevenness of the temperature in the metal substrates can be eliminated. Thus, the durability of the inner wall tiles can be improved. (N.H.)

The resistance of the yeast Saccharomyces cerevisiae to the biocide polyhexamethylene biguanide: involvement of cell wall integrity pathway and emerging role for YAP1

Directory of Open Access Journals (Sweden)

de Morais Marcos A

2011-08-01

Full Text Available Abstract Background Polyhexamethylene biguanide (PHMB is an antiseptic polymer that is mainly used for cleaning hospitals and pools and combating Acantamoeba infection. Its fungicide activity was recently shown by its lethal effect on yeasts that contaminate the industrial ethanol process, and on the PE-2 strain of Saccharomyces cerevisiae, one of the main fermenting yeasts in Brazil. This pointed to the need to know the molecular mechanism that lay behind the cell resistance to this compound. In this study, we examined the factors involved in PHMB-cell interaction and the mechanisms that respond to the damage caused by this interaction. To achieve this, two research strategies were employed: the expression of some genes by RT-qPCR and the analysis of mutant strains. Results Cell Wall integrity (CWI genes were induced in the PHMB-resistant Saccharomyces cerevisiae strain JP-1, although they are poorly expressed in the PHMB-sensitive Saccharomyces cerevisiae PE2 strain. This suggested that PHMB damages the glucan structure on the yeast cell wall. It was also confirmed by the observed sensitivity of the yeast deletion strains, Δslg1, Δrom2, Δmkk2, Δslt2, Δknr4, Δswi4 and Δswi4, which showed that the protein kinase C (PKC regulatory mechanism is involved in the response and resistance to PHMB. The sensitivity of the Δhog1 mutant was also observed. Furthermore, the cytotoxicity assay and gene expression analysis showed that the part played by YAP1 and CTT1 genes in cell resistance to PHMB is unrelated to oxidative stress response. Thus, we suggested that Yap1p can play a role in cell wall maintenance by controlling the expression of the CWI genes. Conclusion The PHMB treatment of the yeast cells activates the PKC1/Slt2 (CWI pathway. In addition, it is suggested that HOG1 and YAP1 can play a role in the regulation of CWI genes.

Mediated oxidation of hydroquinone on poly(N-ethylcarbazole): Analysis of transport and kinetic phenomena by impedance techniques

Energy Technology Data Exchange (ETDEWEB)

Deslouis, C.; Tribollet, B. (Physique des Liquides et Electrochimie Lab., Univ. Pierre et Marie Curie, 75 - Paris (France)); Musiani, M.M. (Ist. di Polarografia ed Elettrochimica Preparativa del CNR, Padua (Italy))

1990-09-01

The oxidation of hydroquinone on Pt electrodes modified by electrosynthesized p-ethylcarbazole is studied in 5 M HClO{sub 4}. Electrohydrodynamical and a.c. impedance measurements yield the redox capacitance of the film and electron diffusivity D{sub E} with reasonable dependence on the thickness. D{sub E} values near to 10{sup -7} cm{sup 2} s{sup -1} confirm the average conductivity of this polymer. Change-transfer resistances in agreement with {alpha}=0.5 are measured. These results {alpha} posteriori justify the hypotheses put forward when developing the theoretical impedance model used for the analysis of the data. (orig.).

Impedance Matching Antenna-Integrated High-Efficiency Energy Harvesting Circuit

Science.gov (United States)

Shinki, Yuharu; Shibata, Kyohei; Mansour, Mohamed

2017-01-01

This paper describes the design of a high-efficiency energy harvesting circuit with an integrated antenna. The circuit is composed of series resonance and boost rectifier circuits for converting radio frequency power into boosted direct current (DC) voltage. The measured output DC voltage is 5.67 V for an input of 100 mV at 900 MHz. Antenna input impedance matching is optimized for greater efficiency and miniaturization. The measured efficiency of this antenna-integrated energy harvester is 60% for −4.85 dBm input power and a load resistance equal to 20 kΩ at 905 MHz. PMID:28763043

Impedance Matching Antenna-Integrated High-Efficiency Energy Harvesting Circuit

Directory of Open Access Journals (Sweden)

Yuharu Shinki

2017-08-01

Full Text Available This paper describes the design of a high-efficiency energy harvesting circuit with an integrated antenna. The circuit is composed of series resonance and boost rectifier circuits for converting radio frequency power into boosted direct current (DC voltage. The measured output DC voltage is 5.67 V for an input of 100 mV at 900 MHz. Antenna input impedance matching is optimized for greater efficiency and miniaturization. The measured efficiency of this antenna-integrated energy harvester is 60% for −4.85 dBm input power and a load resistance equal to 20 kΩ at 905 MHz.

Impedance Matching Antenna-Integrated High-Efficiency Energy Harvesting Circuit.

Science.gov (United States)

Shinki, Yuharu; Shibata, Kyohei; Mansour, Mohamed; Kanaya, Haruichi

2017-08-01

This paper describes the design of a high-efficiency energy harvesting circuit with an integrated antenna. The circuit is composed of series resonance and boost rectifier circuits for converting radio frequency power into boosted direct current (DC) voltage. The measured output DC voltage is 5.67 V for an input of 100 mV at 900 MHz. Antenna input impedance matching is optimized for greater efficiency and miniaturization. The measured efficiency of this antenna-integrated energy harvester is 60% for -4.85 dBm input power and a load resistance equal to 20 kΩ at 905 MHz.

Application of Conductive Carbon Nanotube Fibers and Composites: Gas Sensor

Science.gov (United States)

2013-05-01

changes in Raman spectroscopy data when single wall carbon nanotubes (SWNT) are immersed in various liquids, including common organics (12). In...Resistance -- (82) 2007 Su H2O MWNT PMMA, KOH Gas Impedance -- (83) 2011 Tang H2O MWNT PI Gas Resistance -- (84) 2003 Wang H2O2, NADH SWNT

Recovery of BMIPP uptake and regional wall motion in insulin resistant patients following angioplasty for acute myocardial infarction

Energy Technology Data Exchange (ETDEWEB)

Fujino, Takayuki; Ishii, Yoshinao; Hirasawa, Kunihiko; Tateda, Kunihiko [Asahikawa City Hospital, Hokkaido (Japan); Takeuchi, Toshiharu; Kikuchi, Kenjiro; Hasebe, Naoyuki [Asahikawa Medical Coll., Hokkaido (Japan)

2003-09-01

The effect of insulin resistance (IR) on the fatty acid metabolism of myocardium, and therefore on the recovery of left ventricular (LV) wall motion, has not been established in patients with acute myocardial infarction (AMI). A total of consecutive 58 non-diabetic AMI patients who had successfully undergone emergency coronary angioplasty were analyzed retrospectively. They were categorized into 2 groups, normal glucose tolerance (NGT) and impaired glucose tolerance (IGT), based on a 75-g oral glucose tolerance test (OGTT). The parameters of OGTT, myocardial scintigraphy (n=58) (thallium-201 (Tl) and iodine-123-{beta}-methyl-iodophenylpentadecanoic acid (BMIPP)) and left ventriculography (n=24) were compared in the 2 groups after reperfusion (acute phase) and 3-4 weeks after the AMI (chronic phase). The IR, estimated by the serum concentration of insulin at 120 min (IRI 120') of the OGTT and by the HOMA (the homeostasis model assessment) index, was higher in the IGT group than in NGT group. An inverse correlation was found between the recovery of regional LV wall motion in the ischemic lesion and the IRI 120' and HOMA index. Although the recovery of BMIPP uptake from the acute to the chronic phase was higher in the IGT group, it was only correlated with the degree of IRI 120', not with the HOMA. IR accompanied by IGT can negatively influence the recovery of regional LV wall motion. (author)

Recovery of BMIPP uptake and regional wall motion in insulin resistant patients following angioplasty for acute myocardial infarction

International Nuclear Information System (INIS)

Fujino, Takayuki; Ishii, Yoshinao; Hirasawa, Kunihiko; Tateda, Kunihiko; Takeuchi, Toshiharu; Kikuchi, Kenjiro; Hasebe, Naoyuki

2003-01-01

The effect of insulin resistance (IR) on the fatty acid metabolism of myocardium, and therefore on the recovery of left ventricular (LV) wall motion, has not been established in patients with acute myocardial infarction (AMI). A total of consecutive 58 non-diabetic AMI patients who had successfully undergone emergency coronary angioplasty were analyzed retrospectively. They were categorized into 2 groups, normal glucose tolerance (NGT) and impaired glucose tolerance (IGT), based on a 75-g oral glucose tolerance test (OGTT). The parameters of OGTT, myocardial scintigraphy (n=58) (thallium-201 (Tl) and iodine-123-β-methyl-iodophenylpentadecanoic acid (BMIPP)) and left ventriculography (n=24) were compared in the 2 groups after reperfusion (acute phase) and 3-4 weeks after the AMI (chronic phase). The IR, estimated by the serum concentration of insulin at 120 min (IRI 120') of the OGTT and by the HOMA (the homeostasis model assessment) index, was higher in the IGT group than in NGT group. An inverse correlation was found between the recovery of regional LV wall motion in the ischemic lesion and the IRI 120' and HOMA index. Although the recovery of BMIPP uptake from the acute to the chronic phase was higher in the IGT group, it was only correlated with the degree of IRI 120', not with the HOMA. IR accompanied by IGT can negatively influence the recovery of regional LV wall motion. (author)

Fire resistant nuclear fuel cask

International Nuclear Information System (INIS)

Heckman, R.C.; Moss, M.

1979-01-01

The disclosure is directed to a fire resistant nuclear fuel cask employing reversibly thermally expansible bands between adjacent cooling fins such that normal outward flow of heat is not interfered with, but abnormal inward flow of heat is impeded or blocked

Airtightness of the window-wall interface in masonry brick walls

OpenAIRE

Van Den Bossche, Nathan; Huyghe, Willem; Moens, Jan; Janssens, Arnold

2013-01-01

In recent decades there has been an increased focus on enhanced thermal resistance of building components and as a consequence, the relative importance of airtightness on the overall energy losses of buildings has increased significantly. The construction industry requires practical information on the airtightness of individual construction elements and building envelope interfaces. A literature review on the airtightness of window-wall interfaces has shown that no experimental data are avai...

Concentric artificial impedance surface for directional sound beamforming

Directory of Open Access Journals (Sweden)

Kyungjun Song

2017-03-01

Full Text Available Utilizing acoustic metasurfaces consisting of subwavelength resonant textures, we design an artificial impedance surface by creating a new boundary condition. We demonstrate a circular artificial impedance surface with surface impedance modulation for directional sound beamforming in three-dimensional space. This artificial impedance surface is implemented by revolving two-dimensional Helmholtz resonators with varying internal coiled path. Physically, the textured surface has inductive surface impedance on its inner circular patterns and capacitive surface impedance on its outer circular patterns. Directional receive beamforming can be achieved using an omnidirectional microphone located at the focal point formed by the gradient-impeding surface. In addition, the uniaxial surface impedance patterning inside the circular aperture can be used for steering the direction of the main lobe of the radiation pattern.

Impedance measurements on YB/sub 2/Cu/sub 3/O/sub 7-delta) interpretation and trapping parameters

International Nuclear Information System (INIS)

Yasmeen, S.; Mohammad, M.; Khan, A.Y.; Subhani, M.S.

1997-01-01

Two probe impedance spectroscopic studies were carried out on YBa/sub 2/Cu/sub 3/ O/sub 7-delta/ two different sintering conditions i.e. at before final sintering and at after final sintering. In both condition ac impedance studies were done in the frequency range of 1Hz to 100kHz and at different temperatures from room temperature down to 78K. Measurements were done with contacts opposite side (i.e., ceramic behaves as a resister) as well as on opposite sides (i.e., ceramic behaves as a capacitor). Results were obtained in the form of Nyquist plot. Log, Yi/omega Vs log f plot and Yr/omega Vs log f plot. These plots were explained through equivalent circuits. The bulk resistance Rb, the grain boundary resistance R/sub b/ and grain boundary capacitance C/sub gb/ were obtained through these plots. The ac conductivities were also obtained at all temperatures. The log sigma g Vs log omega (frequency) plots were interpreted invoking the theory of ac conductivity in polycrystalline solids. The trapping parameters (binding energy, the hopping distance etc.) were calculated and interpreted. (author)

Tapping mode microwave impedance microscopy

KAUST Repository

Lai, K.; Kundhikanjana, W.; Peng, H.; Cui, Y.; Kelly, M. A.; Shen, Z. X.

2009-01-01

We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately

Altered electrode degradation with temperature in LiFePO4/mesocarbon microbead graphite cells diagnosed with impedance spectroscopy

International Nuclear Information System (INIS)

Klett, Matilda; Zavalis, Tommy Georgios; Kjell, Maria H.; Lindström, Rakel Wreland; Behm, Mårten; Lindbergh, Göran

2014-01-01

Highlights: • Aging of LiFePO 4 /mesocarbon microbead graphite cells from hybrid electric vehicle cycling. • Electrode degradation evaluated post-mortem by impedance spectroscopy and physics-based modeling. • Increased temperature promotes different degradation processes on the electrode level. • Conductive carbon degradation at 55 °C in the LiFePO 4 electrode. • Mesocarbon microbead graphite electrode degraded by cycling rather than temperature. - Abstract: Electrode degradation in LiFePO 4 /mesocarbon microbead graphite (MCMB) pouch cells aged at 55 °C by a synthetic hybrid drive cycle or storage is diagnosed and put into context with previous results of aging at 22 °C. The electrode degradation is evaluated by means of electrochemical impedance spectroscopy (EIS), measured separately on electrodes harvested from the cells, and by using a physics-based impedance model for aging evaluation. Additional capacity measurements, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) are used in the evaluation. At 55 °C the LiFePO 4 electrode shows increased particle/electronic conductor resistance, for both stored and cycled electrodes. This differs from results obtained at 22 °C, where the electrode suffered lowered porosity, particle fracture, and loss of active material. For graphite, only cycling gave a sustained effect on electrode performance at 55 °C due to lowered porosity and changes of surface properties, and to greater extent than at low temperature. Furthermore, increased current collector resistance also contributes to a large part of the pouch cell impedance when aged at increased temperatures. The result shows that increased temperature promotes different degradation on the electrode level, and is an important implication for high temperature accelerated aging. In light of the electrode observations, the correlation between full-cell and electrode impedances is discussed

Electronic properties of single-walled chiral carbon nanotube

International Nuclear Information System (INIS)

Mensah, S.Y.; Allotey, F.K.A.; Mensah, N.G.; Nkrumah, G.

2001-09-01

The electronic properties of single-walled chiral carbon nanotube has been studied using the model based on infinitely long carbon atoms wrapped along a base helix of single-walled carbon nanotubes(SWNTs). The problem is solved semiclassically, and current density J, resistivity ρ, thermopower α z , and electrical power factor P calculated. It is noted that the current density j displays negative differential conductivity, whiles the resistivity ρ increases with increasing electrical field. ρ also slowly increases at low temperatures and then gradually increases with increasing temperature. The thermopower α z shows interesting behaviour. Very intriguing is the electrical power factor which shows relatively large values. (author)

Development of Adaptive Acoustic Impedance Control Technologies of Acoustic Duct Liner

Directory of Open Access Journals (Sweden)

Hiroshi Kobayashi

2011-01-01

Full Text Available This paper describes the development of adaptive acoustic impedance control (AAC technologies to achieve a larger fan noise reduction, by adaptively adjusting reactance and resistance of the acoustic liner impedance. For the actual proof of the AAC technology III performance, the advanced fan noise absorption control duct liner II was made on trial basis, with the simple control system and the plain device. And, then, the duct liner II was examined for the AAC technology I, II, and III models, using the high speed fan test facility. The test results made clear that the duct liner II of the AAC technology III model could achieve the fan noise reduction higher than O.A. SPL 10 dB (A at the maximum fan speed 6000 rpm, containing the reduction of fundamental BPF tone of 18 dB and 2nd BPF tone of 10 dB in response to the fan peed change from 3000 to 6000 rpm.

Resistive wall wakefields of short bunches at cryogenic temperatures

Directory of Open Access Journals (Sweden)

G. Stupakov

2015-03-01

Full Text Available We present calculations of the longitudinal wakefields at cryogenic temperatures for extremely short bunches, characteristic for modern x-ray free electron lasers. The calculations are based on the equations for the surface impedance in the regime of the anomalous skin effect in metals. This paper extends and complements an earlier analysis of B. Podobedov, Phys. Rev. ST Accel. Beams 12, 044401 (2009. into the region of very high frequencies associated with bunch lengths in the micron range. We study in detail the case of a rectangular bunch distribution for parameters of interest of LCLS-II with a superconducting undulator.

Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems

KAUST Repository

Bera, Tushar Kanti

2016-03-18

Abstract: Electrical impedance tomography (EIT) phantoms are essential for the calibration, comparison and evaluation of the EIT systems. In EIT, the practical phantoms are typically developed based on inhomogeneities surrounded by a homogeneous background to simulate a suitable conductivity contrast. In multifrequency EIT (Mf-EIT) evaluation, the phantoms must be developed with the materials which have recognizable or distinguishable impedance variations over a wide range of frequencies. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity are analyzed. A number of practical phantoms with different tissue inhomogeneities and different inhomogeneity configurations are developed and the multifrequency impedance imaging is studied with the Mf-EIT system to evaluate the phantoms. The conductivity of the vegetable inhomogeneities reconstructed from the EIT imaging is compared with the conductivity values obtained from the EIS studies. Experimental results obtained from multifrequency EIT reconstruction demonstrate that the electrical impedance of all the biological tissues inhomogenity decreases with frequency. The potato tissue phantom produces better impedance image in high frequency ranges compared to the cucumber phantom, because the cucumber impedance at high frequency becomes lesser than that of the potato at the same frequency range. Graphical Abstract: [Figure not available: see fulltext.] © 2016 The Visualization Society of Japan

Experimental diagnostics and modeling of inductive phenomena at low frequencies in impedance spectra of proton exchange membrane fuel cells

Science.gov (United States)

Pivac, Ivan; Šimić, Boris; Barbir, Frano

2017-10-01

Representation of fuel cell processes by equivalent circuit models, involving resistance and capacitance elements representing activation losses on both anode and cathode in series with resistance representing ohmic losses, cannot capture and explain the inductive loop that may show up at low frequencies in Nyquist diagram representation of the electrochemical impedance spectra. In an attempt to explain the cause of the low-frequency inductive loop and correlate it with the processes within the fuel cell electrodes, a novel equivalent circuit model of a Proton Exchange Membrane (PEM) fuel cell has been proposed and experimentally verified here in detail. The model takes into account both the anode and the cathode, and has an additional resonant loop on each side, comprising of a resistance, capacitance and inductance in parallel representing the processes within the catalyst layer. Using these additional circuit elements, more accurate and better fits to experimental impedance data in the wide frequency range at different current densities, cell temperatures, humidity of gases, air flow stoichiometries and backpressures were obtained.

Exploratory study on the methodology of fast imaging of unilateral stroke lesions by electrical impedance asymmetry in human heads.

Science.gov (United States)

Ma, Jieshi; Xu, Canhua; Dai, Meng; You, Fusheng; Shi, Xuetao; Dong, Xiuzhen; Fu, Feng

2014-01-01

Stroke has a high mortality and disability rate and should be rapidly diagnosed to improve prognosis. Diagnosing stroke is not a problem for hospitals with CT, MRI, and other imaging devices but is difficult for community hospitals without these devices. Based on the mechanism that the electrical impedance of the two hemispheres of a normal human head is basically symmetrical and a stroke can alter this symmetry, a fast electrical impedance imaging method called symmetrical electrical impedance tomography (SEIT) is proposed. In this technique, electrical impedance tomography (EIT) data measured from the undamaged craniocerebral hemisphere (CCH) is regarded as reference data for the remaining EIT data measured from the other CCH for difference imaging to identify the differences in resistivity distribution between the two CCHs. The results of SEIT imaging based on simulation data from the 2D human head finite element model and that from the physical phantom of human head verified this method in detection of unilateral stroke.

Lipid Bilayer Membrane in a Silicon Based Micron Sized Cavity Accessed by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy.

Science.gov (United States)

Khan, Muhammad Shuja; Dosoky, Noura Sayed; Patel, Darayas; Weimer, Jeffrey; Williams, John Dalton

2017-07-05

Supported lipid bilayers (SLBs) are widely used in biophysical research to probe the functionality of biological membranes and to provide diagnoses in high throughput drug screening. Formation of SLBs at below phase transition temperature ( Tm ) has applications in nano-medicine research where low temperature profiles are required. Herein, we report the successful production of SLBs at above-as well as below-the Tm of the lipids in an anisotropically etched, silicon-based micro-cavity. The Si-based cavity walls exhibit controlled temperature which assist in the quick and stable formation of lipid bilayer membranes. Fusion of large unilamellar vesicles was monitored in real time in an aqueous environment inside the Si cavity using atomic force microscopy (AFM), and the lateral organization of the lipid molecules was characterized until the formation of the SLBs. The stability of SLBs produced was also characterized by recording the electrical resistance and the capacitance using electrochemical impedance spectroscopy (EIS). Analysis was done in the frequency regime of 10 -2 -10⁵ Hz at a signal voltage of 100 mV and giga-ohm sealed impedance was obtained continuously over four days. Finally, the cantilever tip in AFM was utilized to estimate the bilayer thickness and to calculate the rupture force at the interface of the tip and the SLB. We anticipate that a silicon-based, micron-sized cavity has the potential to produce highly-stable SLBs below their Tm . The membranes inside the Si cavity could last for several days and allow robust characterization using AFM or EIS. This could be an excellent platform for nanomedicine experiments that require low operating temperatures.

Asymmetrical Grid Fault Ride-Through Strategy of Three-phase Grid-connected Inverter Considering Network Impedance Impact in Low Voltage Grid

DEFF Research Database (Denmark)

Guo, Xiaoqiang; Zhang, Xue; Wang, Baocheng

2014-01-01

This letter presents a new control strategy of threephase grid-connected inverter for the positive sequence voltage recovery and negative sequence voltage reduction under asymmetrical grid faults. Unlike the conventional control strategy based on an assumption that the network impedance is mainly...... of the proposed solution for the flexible voltage support in a low-voltage grid, where thenetwork impedance is mainly resistive.......This letter presents a new control strategy of threephase grid-connected inverter for the positive sequence voltage recovery and negative sequence voltage reduction under asymmetrical grid faults. Unlike the conventional control strategy based on an assumption that the network impedance is mainly...... inductive, the proposed control strategy is more flexible and effective by considering the network impedance impact, which is of great importance for the high penetration of grid-connected renewable energy systems into low-voltage grids. The experimental tests are carried out to validate the effectiveness...

Fractional Order Element Based Impedance Matching

KAUST Repository

Radwan, Ahmed Gomaa

2014-06-24

Disclosed are various embodiments of methods and systems related to fractional order element based impedance matching. In one embodiment, a method includes aligning a traditional Smith chart (|.alpha.|=1) with a fractional order Smith chart (|.alpha.|.noteq.1). A load impedance is located on the traditional Smith chart and projected onto the fractional order Smith chart. A fractional order matching element is determined by transitioning along a matching circle of the fractional order Smith chart based at least in part upon characteristic line impedance. In another embodiment, a system includes a fractional order impedance matching application executed in a computing device. The fractional order impedance matching application includes logic that obtains a first set of Smith chart coordinates at a first order, determines a second set of Smith chart coordinates at a second order, and determines a fractional order matching element from the second set of Smith chart coordinates.

Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems

KAUST Repository

Bera, Tushar Kanti; Nagaraju, J.; Lubineau, Gilles

2016-01-01

. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity

Influence of intensive light exposure on the complex impedance of polymer light-emitting diodes

Directory of Open Access Journals (Sweden)

Fábio Rogério Cury

2008-06-01

Full Text Available In this work we investigated the effect of visible radiation on the electrical properties of poly[(2-methoxy-5-hexyloxy-p-phenylenevinylene]- MH-PPV films and light emitting diodes. Complex impedance measurements of (Au or ITO/MH-PPV/(Au or Al samples were carried out at room temperature and exposed to white light. Over the frequency range from 100 mHz to 2 MHz, the electrical results of Au/MH-PPV/Au was dominated by the Cole-Cole approach, where the electrode influence is negligible. However, some additional influence of the interface was observed to occur when Al was used as electrode. These effects were observed under both dark and visible-light illumination conditions. A simple model based on resistor-capacitor parallel circuits was developed to represent the complex impedance of the samples, thereby separating bulk and interface contributions. We observed that the polymer electrical resistivity decreased while the dielectric constant of the polymer and the thickness of the Al/MH-PPV layer were almost constant with increasing light intensity. The decrease of the polymer layer resistance comes from a better charge injection due to a light induced dissociation of positive charge carriers at the electrode.

INVESTIGATION OF CEMENT CONCRETE CONGLOMERATE SOLIDIFICATION PROCESS BY IMPEDANCE SPECTROSCOPY METHOD

Directory of Open Access Journals (Sweden)

S. N. Bandarenka

2015-01-01

Full Text Available One of the most prospective directions in preservation  and increase of service live of  road pavements is a construction of  automobile roads with cement concrete surface. Modern tendencies for provision of road construction quality presuppose a necessity to control processes of solidification and subsequent destruction of the material while forming and using cement concrete conglomerate being considered as a basic element of the road surface.  Multiyear practical experience of  automobile road operation using cement concrete pavements reveals an importance for monitoring  such processes as formation and destruction of cement concrete materials. An impedance spectroscopy method has been tried out and proposed as a tool for solution of the given problem.Experimental samples of cement concrete have been prepared for execution of tests, graded silica sand and granite chippings with particle size from 0.63 to 2.5 mm have been used as a fine aggregate in the samples. Dependencies of resistance (impedance on AC-current frequency  have been studied for samples of various nature and granulometric composition. The Gamry  G300 potentiostat has been used for measurement of complex impedance value. A spectrum analysis and calculation of equivalent circuit parameters calculation have been carried out while using EIS Spectrum Analyzer program.Comparison of impedance spectra for the prepared cement concrete samples have made it possible to reveal tendencies in changing spectrum parameters during solidification and subsequent contact with moisture in respect of every type of the sample. An equivalent electrical circuit has been developed that  characterizes physical and chemical processes which are accompanied by charge transfer in cement concrete conglomerate. The paper demonstrates a possibility to use an impedance spectroscopy for solution of a number of actual problems in the field of cement concrete technology problems. Particularly, the problems

Methods for calculating the electrode position Jacobian for impedance imaging.

Science.gov (United States)

Boyle, A; Crabb, M G; Jehl, M; Lionheart, W R B; Adler, A

2017-03-01

Electrical impedance tomography (EIT) or electrical resistivity tomography (ERT) current and measure voltages at the boundary of a domain through electrodes. The movement or incorrect placement of electrodes may lead to modelling errors that result in significant reconstructed image artifacts. These errors may be accounted for by allowing for electrode position estimates in the model. Movement may be reconstructed through a first-order approximation, the electrode position Jacobian. A reconstruction that incorporates electrode position estimates and conductivity can significantly reduce image artifacts. Conversely, if electrode position is ignored it can be difficult to distinguish true conductivity changes from reconstruction artifacts which may increase the risk of a flawed interpretation. In this work, we aim to determine the fastest, most accurate approach for estimating the electrode position Jacobian. Four methods of calculating the electrode position Jacobian were evaluated on a homogeneous halfspace. Results show that Fréchet derivative and rank-one update methods are competitive in computational efficiency but achieve different solutions for certain values of contact impedance and mesh density.

Study of Local and Distortional Stability of Thin-Walled Structures

Directory of Open Access Journals (Sweden)

Imene Mahi

2018-01-01

Full Text Available Thin-walled structures have an increasingly large and growing field of application in the engineering sector, the goal behind using this type of structure is efficiency in terms of resistance and cost, however the stability of its components (the thin walls remains the first aspect of the behavior, and a primordial factor in the design process. The hot rolled sections are known by a consequent post-buckling reserve, cold-formed steel sections which are thin-walled elements also benefit, in this case, it seems essential to take into account the favorable effects of this reserve in to the verification procedure of the resistance with respect to the three modes of failures of this type of structure. The design method that takes into account this reserve of resistance is inevitably the effective width method. The direct strength method has been developed to improve the speed and efficiency of the design of thin-walled profiles. The latter mainly uses the buckling loads (for Local, Distortional and Global mode obtained from a numerical analysis and the resistance curves calibrated experimentally to predict the ultimate load of the profile. Among those, the behavior of a set of Cshaped profiles (highly industrialized is studied, this type of section is assumed to be very prone to modes of local and distortional instability. The outcome of this investigation revealed very relevant conclusions both scientifically and practically.

Estimating the short-circuit impedance

DEFF Research Database (Denmark)

Nielsen, Arne Hejde; Pedersen, Knud Ole Helgesen; Poulsen, Niels Kjølstad

1997-01-01

A method for establishing a complex value of the short-circuit impedance from naturally occurring variations in voltage and current is discussed. It is the symmetrical three phase impedance at the fundamental grid frequency there is looked for. The positive sequence components in voltage...... and current are derived each period, and the short-circuit impedance is estimated from variations in these components created by load changes in the grid. Due to the noisy and dynamic grid with high harmonic distortion it is necessary to threat the calculated values statistical. This is done recursively...... through a RLS-algorithm. The algorithms have been tested and implemented on a PC at a 132 kV substation supplying a rolling mill. Knowing the short-circuit impedance gives the rolling mill an opportunity to adjust the arc furnace operation to keep flicker below a certain level. Therefore, the PC performs...

Fabrication of a carbon nanotube-based gas sensor using dielectrophoresis and its application for ammonia detection by impedance spectroscopy

International Nuclear Information System (INIS)

Suehiro, Junya; Zhou Guangbin; Hara, Masanori

2003-01-01

This paper describes a new method for fabricating a gas sensor composed of multi-wall carbon nanotubes (MWCNTs) using dielectrophoresis (DEP). MWCNTs dispersed in ethanol were trapped and enriched in an interdigitated microelectrode gap under the action of a positive DEP force that drove the MWCNTs to a higher electric field region. During the trapping of MWCNTs, the electrode impedance varied as the number of MWCNTs bridging the electrode gap increased. After the DEP process, the ethanol was evaporated and the microelectrode retaining the MWCNTs was exposed to ammonia (NH 3 ) gas while the electrode impedance was monitored. It was found that the electrode impedance was altered by ppm-levels of ammonia at room temperature. The ammonia exposure decreased the sensor conductance, while the capacitance increased. The sensor showed a reversible response with a time constant of a few minutes. The conductance change was proportional to ammonia concentration below 10 ppm and then gradually saturated at higher concentrations. Effects of the number of trapped MWCNTs on sensor response were also discussed. (rapid communication)

Journal bearing impedance descriptions for rotordynamic applications

NARCIS (Netherlands)

Childs, D.W.; Moes, H.; Leeuwen, van H.J.

1977-01-01

Bearing impedance vectors are introduced for plain journal bearings which define the bearing reaction force components as a function of the bearing motion. Impedance descriptions are developed directly for the approximate Ocvirk (short) and Sommerfeld (long) bearing solutions. The impedance vector

Impedance of porous IT-SOFC LSCF:CGO composite cathodes

DEFF Research Database (Denmark)

Nielsen, Jimmi; Jacobsen, Torben; Wandel, Marie

2011-01-01

The impedance of technological relevant LSCF:CGO composite IT-SOFC cathodes was studied over a very wide performance range. This was experimentally achieved by impedance measurements on symmetrical cells with three different microstructures in the temperature range 550–850 °C. In order to account...... for the impedance spectra of the poor performing cathodes the Finite-Length-Gerischer (FLG) impedance was derived and applied to the impedance data. The FLG impedance describes for a given microstructure the situation where the cathode is made too thin from a cathode development point of view. The moderate...... performing cathodes showed a slightly suppressed Gerischer impedance, while the impedance spectra of the well performing cathodes showed the presence of an arc due to oxygen gas diffusion. The overall impedance of the well performing cathodes could be described with a slightly suppressed Gerischer impedance...

Measurement of electrical impedance of a Berea sandstone core during the displacement of saturated brine by oil and CO2 injections

Science.gov (United States)

Liu, Yu; Xue, Ziqiu; Park, Hyuck; Kiyama, Tamotsu; Zhang, Yi; Nishizawa, Osamu; Chae, Kwang-seok

2015-12-01

Complex electrical impedance measurements were performed on a brine-saturated Berea sandstone core while oil and CO2 were injected at different pressures and temperatures. The saturations of brine, oil, and CO2 in the core were simultaneously estimated using an X-ray computed tomography scanner. The formation factor of this Berea core and the resistivity indexes versus the brine saturations were calculated using Archie's law. The experimental results found different flow patterns of oil under different pressures and temperatures. Fingers were observed for the first experiment at 10 MPa and 40 °C. The fingers were restrained as the viscosity ratio of oil and water changed in the second (10 MPa and 25 °C) and third (5 MPa and 25 °C) experiments. The resistivity index showed an exponential increase with a decrease in brine saturation. The saturation exponent varied from 1.4 to 4.0 at different pressure and temperature conditions. During the oil injection procedure, the electrical impedance increased with oil saturation and was significantly affected by different oil distributions; therefore, the impedance varied whether the finger was remarkable or not, even if the oil saturation remained constant. During the CO2 injection steps, the impedance showed almost no change with CO2 saturation because the brine in the pores became immobile after the oil injection.

Performance characteristics of plane-wall venturi-like reverse flow diverters

International Nuclear Information System (INIS)

Smith, G.V.; Counce, R.M.

1982-01-01

The results of an analytical and experimental study of plane-wall venturi-like reverse flow diverters (RFD) are presented. In general, the flow characteristics of the RFD are reasonably well predicted by the mathematical model of the RFD, although a divergence between theory and data is observed for the output characteristics in the reverse flow mode as the output impedance is reduced. Overall, the performance of these devices indicates their usefulness in fluid control and fluid power systems, such as displacement pumping systems

Cell wall composition profiling of parasitic giant dodder (Cuscuta reflexa) and its hosts: a priori differences and induced changes.

Science.gov (United States)

Johnsen, Hanne R; Striberny, Bernd; Olsen, Stian; Vidal-Melgosa, Silvia; Fangel, Jonatan U; Willats, William G T; Rose, Jocelyn K C; Krause, Kirsten

2015-08-01

Host plant penetration is the gateway to survival for holoparasitic Cuscuta and requires host cell wall degradation. Compositional differences of cell walls may explain why some hosts are amenable to such degradation while others can resist infection. Antibody-based techniques for comprehensive profiling of cell wall epitopes and cell wall-modifying enzymes were applied to several susceptible hosts and a resistant host of Cuscuta reflexa and to the parasite itself. Infected tissue of Pelargonium zonale contained high concentrations of de-esterified homogalacturonans in the cell walls, particularly adjacent to the parasite's haustoria. High pectinolytic activity in haustorial extracts and high expression levels of pectate lyase genes suggest that the parasite contributes directly to wall remodeling. Mannan and xylan concentrations were low in P. zonale and in five susceptible tomato introgression lines, but high in the resistant Solanum lycopersicum cv M82, and in C. reflexa itself. Knowledge of the composition of resistant host cell walls and the parasite's own cell walls is useful in developing strategies to prevent infection by parasitic plants. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Expression and characterization of a novel spore wall protein from ...

African Journals Online (AJOL)