WorldWideScience

Sample records for current ac iontophoretic

  1. Correlation of transdermal iontophoretic phenylalanine and mannitol transport: test of the internal standard concept under DC iontophoresis and constant resistance AC iontophoresis conditions.

    Science.gov (United States)

    Yan, Guang; Higuchi, William I; Szabo, Aniko; Li, S Kevin

    2004-07-23

    The purpose of this study was to test the feasibility of using an internal standard approach to predict the transdermal flux of phenylalanine (Phe) across human epidermal membrane (HEM) in vitro during iontophoresis of constant direct current (DC), constant skin resistance alternating current (AC) with DC offset (AC-plus-DC), symmetric constant resistance AC (AC-only), and constant current DC with the application of a polyelectrolyte. Under the constant current DC and AC-plus-DC conditions, a linear relationship between the permeation of Phe and that of mannitol was observed with a slope close to unity. The ratios of the Phe permeability coefficients to those of mannitol during iontophoresis with different HEM samples were essentially constant with significantly smaller inter-sample and intra-sample variabilities than those of the raw Phe permeability coefficient data. This demonstrates that mannitol is a good internal standard for predicting the transdermal iontophoretic flux of Phe under these two conditions. On the other hand, the correlations of the permeability coefficients of Phe and mannitol under the AC-only iontophoresis and iontophoresis with the polyelectrolyte are poorer than those observed during DC and AC-plus-DC iontophoresis. The poor correlations are believed to be related to Phe being a zwitterion and its anionic form in HEM. Previously, iontophoretic transport of glucose has been demonstrated to be essentially the same as that of mannitol. The good correlations between Phe and mannitol transport across HEM during DC and AC-plus-DC iontophoresis in the present study therefore suggest that glucose and its extraction can be used as the internal standard for iontophoretic Phe monitoring.

  2. Iontophoretic Permeation of Lisinopril at Different Current Densities and Drug Concentrations

    Directory of Open Access Journals (Sweden)

    Ashish Jain

    2012-08-01

    Full Text Available Purpose: The purpose of the present work was to assess iontophoretic permeation of Lisinopril at different current densities and concentrations for development of patient-controlled active transdermal system. Methods: In vitro iontophoretic transdermal delivery of Lisinopril across the pigskin was investigated at three different drug concentrations and three different current densities (0.25- 0.75 mA/cm2 in the donor cell of the diffusion apparatus, using cathodal iontophoresis along with the passive controls. Results: For passive permeation, the steady state flux significantly increased with the increasing of donor drug concentration. At all concentration levels, iontophoresis considerably increased the permeation rate compared to passive controls. Iontophoretic transport of Lisinopril was to be found increase with current densities. Flux enhancement was highest at the lowest drug load and lowest at the highest drug load. Conclusion: The obtained results indicate that permeation rate of Lisinopril across the pigskin can be considerably enhanced, controlled or optimized by the use of Iontophoresis technique.

  3. Total AC loss of YBCO coated conductor carrying AC transport current in AC transverse magnetic field with various orientations

    Energy Technology Data Exchange (ETDEWEB)

    Amemiya, Naoyuki [Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501 (Japan); Jiang, Zhenan [Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501 (Japan); Iijima, Yasuhiro [Materials Research Laboratory, Fujikura Ltd, 1-5-1 Kiba, Koto, Tokyo 135-8512 (Japan); Kakimoto, Kazuomi [Materials Research Laboratory, Fujikura Ltd, 1-5-1 Kiba, Koto, Tokyo 135-8512 (Japan); Saitoh, Takashi [Materials Research Laboratory, Fujikura Ltd, 1-5-1 Kiba, Koto, Tokyo 135-8512 (Japan)

    2004-08-01

    Using an electro-magnetic method, we measured the total AC loss of a YBCO coated conductor carrying an AC transport current in an AC transverse magnetic field with various orientations. We measured the magnetization loss (energy flow from the external magnetic field) and the transport loss (energy flow from the transport current circuit) independently during simultaneous application of an AC transverse magnetic field and AC transport current. Their sum gave us the total AC loss. The transport loss increases with increasing AC transverse magnetic field, and the magnetization loss increases with increasing AC transport current. The AC transverse magnetic field and the AC self magnetic field interact with each other at the conductor edges. This nonlinear interaction is a possible cause of the increase in AC loss. Due to the high aspect ratio of YBCO coated conductors, this increase in AC loss due to the interaction between the AC transverse and AC self magnetic fields is observed even when the transverse magnetic field is nearly parallel to the conductor wide-face. When the total AC losses for various transport currents and various field orientations are plotted against a transverse magnetic field component which is perpendicular to the conductor wide-face, the plots with different field angles but identical transport current all agree quite well with each other. The total AC loss is dominated by the self magnetic field and the perpendicular component of the transverse magnetic field, both of which mostly penetrate from the conductor edges.

  4. Iontophoretic transdermal delivery of glycyrrhizin: effects of pH, drug concentration, co-ions, current intensity, and chemical enhancers.

    Science.gov (United States)

    Yamamoto, Rie; Takasuga, Shinri; Kominami, Katsuya; Sutoh, Chiyo; Kinoshita, Mine; Kanamura, Kiyoshi; Takayama, Kozo

    2013-01-01

    The aim of the present study was to evaluate the feasibility of transdermal delivery of glycyrrhizin, an agent used in the treatment of chronic hepatitis C, by cathodal iontophoresis using Ag/AgCl electrodes in vitro. The effects of donor pH (pH 4-7), concentration of drug (0.025-0.2% (w/v)), concentration of external chloride ions (Cl(-)) (0-133 mM), current strength (0-0.5 mA/cm(2)), and permeation enhancers (urea and Tween 80) on the skin permeability of glycyrrhizin were examined in in vitro skin permeation studies using porcine ear skin as the membrane. The cumulative amount of permeated glycyrrhizin and the steady-state skin permeation flux of glycyrrhizin across porcine skin increased in a pH-dependent manner. The skin permeability of glycyrrhizin was independent of the concentration of drug and competed only with a high external Cl(-) concentration. The skin permeation flux of glycyrrhizin increased with the current (R(2)=0.8955). The combination of iontophoresis and enhancers provided an additive or synergistic effect, and a skin permeation flux of about 60 µg/h/cm(2) was achieved. The plasma concentration of glycyrrhizin in humans, extrapolated from the in vitro steady-state permeation flux across porcine skin, was within the therapeutic level. These results suggest that cathodal iontophoresis can be used as a transdermal drug delivery system for glycyrrhizin using reasonable patch sizes and acceptable levels of current intensity.

  5. Transcranial alternating current stimulation (tACS

    Directory of Open Access Journals (Sweden)

    Andrea eAntal

    2013-06-01

    Full Text Available Transcranial alternating current stimulation (tACS seems likely to open a new era of the field of noninvasive electrical stimulation of the human brain by directly interfering with cortical rhythms. It is expected to synchronize (by one single resonance frequency or desynchronize (e.g. by the application of several frequencies cortical oscillations. If applied long enough it may cause neuroplastic effects. In the theta range it may improve cognition when applied in phase. Alpha rhythms could improve motor performance, whereas beta intrusion may deteriorate them. TACS with both alpha and beta frequencies has a high likelihood to induce retinal phosphenes. Gamma intrusion can possibly interfere with attention. Stimulation in the ripple range induces intensity dependent inhibition or excitation in the motor cortex most likely by entrainment of neuronal networks, whereas stimulation in the low kHz range induces excitation by neuronal membrane interference. TACS in the 200 kHz range may have a potential in oncology.

  6. Effect of the magnetic material on AC losses in HTS conductors in AC magnetic field carrying AC transport current

    Science.gov (United States)

    Wan, Xing-Xing; Huang, Chen-Guang; Yong, Hua-Dong; Zhou, You-He

    2015-11-01

    This paper presents an investigation on the AC losses in several typical superconducting composite conductors using the H-formulation model. A single superconducting strip with ferromagnetic substrate or cores and a stack of coated conductors with ferromagnetic substrates are studied. We consider all the coated conductors carrying AC transport currents and simultaneously exposed to perpendicular AC magnetic fields. The influences of the amplitude, frequency, phase difference and ferromagnetic materials on the AC losses are investigated. The results show that the magnetization losses of single strip and stacked strips have similar characteristics. The ferromagnetic substrate can increase the magnetization loss at low magnetic field, and decrease the loss at high magnetic field. The ferromagnetic substrate can obviously increase the transport loss in stacked strips. The trends of total AC losses of single strip and stacked strips are similar when they are carrying current or exposed to a perpendicular magnetic field. The effect of the frequency on the total AC losses of single strip is related to the amplitude of magnetic field. The AC losses decrease with increasing frequency in low magnetic field region while increase in high magnetic field region. As the phase difference changes, there is a periodic variation for the AC losses. Moreover, when the strip is under only the transport current and magnetic field, the ferromagnetic cores will increase the AC losses for large transport current or field.

  7. Iontophoretic transdermal delivery of buspirone hydrochloride in hairless mouse skin.

    Science.gov (United States)

    Al-Khalili, Mohammad; Meidan, Victor M; Michniak, Bozena B

    2003-01-01

    The transdermal delivery of buspirone hydrochloride across hairless mouse skin and the combined effect of iontophoresis and terpene enhancers were evaluated in vitro using Franz diffusion cells. Iontophoretic delivery was optimized by evaluating the effect of drug concentration, current density, and pH of the vehicle solution. Increasing the current density from 0.05 to 0.1 mA/cm2 resulted in doubling of the iontophoretic flux of buspirone hydrochloride, while increasing drug concentration from 1% to 2% had no effect on flux. Using phosphate buffer to adjust the pH of the drug solution decreased the buspirone hydrochloride iontophoretic flux relative to water solutions. Incorporating buspirone hydrochloride into ethanol:water (50:50 vol/vol) based gel formulations using carboxymethylcellulose and hydroxypropylmethylcellulose had no effect on iontophoretic delivery. Incorporation of three terpene enhancers (menthol, cineole, and terpineol) into the gel resulted in a synergistic effect when combined with iontophoresis. Menthol was the most active enhancer, and when combined with iontophoresis it was possible to deliver 10 mg/cm2/day of buspirone hydrochloride.

  8. Transdermal iontophoretic delivery of timolol maleate

    Directory of Open Access Journals (Sweden)

    Mayur Patni

    2012-12-01

    Full Text Available Transdermal iontophoresis would be a promising method for the systemic delivery of water soluble and ionic drugs of relatively high molecular size, including peptides. The objective of the present study was to investigate the effect of biological variable such as guinea pig and human cadaver skin and other variables like drug concentration, current density on the transdermal iontophoretic transport of timolol maleate. The permeation profile of drug using solution and gel formulation was studied and compared. For better bioavailability, better patient compliance, and enhanced delivery, an iontophoretic drug delivery system of a timolol maleate matrix gel was formulated using Carbopol 974P. The study was conducted using silver-silver chloride electrodes across the guinea pig and human cadaver skin. Viscosity measurements and flux calculations indicated the suitability of the Carbopol 974P gel for transdermal iontophoretic delivery of timolol maleate. Anodal iontophoresis with silver-silver chloride electrode significantly increased the timolol maleate skin permeation as compared with the passive permeation study. The amount of timolol maleate transported during iontophoresis was significantly different among the different skins. However, iontophoretic gel formulations provided required flux of drug through human cadaver skin.A iontoforese transdérmica seria um método promissor para a liberação sistêmica de fármacos solúveis em água e iônicos de relativamente elevado tamanho molecular, incluindo peptídeos. O objetivo do presente estudo foi investigar o efeito da variável biológica, tais como cobaia e pele de cadáver humano, e outras variáveis como concentração do fármaco, densidade de corrente sobre o transporte transdérmico iontoforético de maleato de timolol. Comparou-se o perfil de permeação do fármaco usando a formulação de solução e de gel. Para melhor biodisponibilidade, melhor adesão do paciente e libera

  9. Modelling ac ripple currents in HTS coated conductors

    Science.gov (United States)

    Xu, Zhihan; Grilli, Francesco

    2015-10-01

    Dc transmission using high temperature superconducting (HTS) coated conductors (CCs) offers a promising solution to the globally growing demand for effective, reliable and economic transmission of green energy up to the gigawatt level over very long distances. The credible estimation of the losses and thereby the heat dissipation involved, where ac ripples (introduced in rectification/ac-dc conversion) are viewed as a potential source of notable contribution, is highly essential for the rational design of practical HTS dc transmission cables and corresponding cryogenic systems to fulfil this demand. Here we report a targeted modelling study into the ac losses in a HTS CC subject to dc and ac ripple currents simultaneously, by solving Maxwell’s equations using the finite element method (FEM) in the commercial software package COMSOL. It is observed that the instantaneous loss exhibits only one peak per cycle in the HTS CC subject to sinusoidal ripples, given that the amplitude of the ac ripples is smaller than approximately 20% of that of the dc current. This is a distinct contrast to the usual observation of two peaks per cycle in a HTS CC subject to ac currents only. The unique mechanism is also revealed, which is directly associated with the finding that, around any local minima of the applied ac ripples, the critical state of -J c is never reached at the edges of the HTS CC, as it should be according to the Bean model. When running further into the longer term, it is discovered that the ac ripple loss of the HTS CC in full-wave rectification decays monotonically, at a speed which is found to be insensitive to the frequency of the applied ripples within our targeted situations, to a relatively low level of approximately 1.38 × 10-4 W m-1 in around 1.7 s. Comparison between this level and other typical loss contributions in a HTS dc cable implies that ac ripple currents in HTS CCs should only be considered as a minor source of dissipation in superconducting dc

  10. Current Control of Grid Converters Connected with Series AC Capacitor

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang

    2015-01-01

    The series ac capacitor has recently been used with the transformerless grid-connected converters in the distribution power grids. The capacitive characteristic of the resulting series LC filter restricts the use of conventional synchronous integral or stationary resonant current controllers. Thus...

  11. Iontophoretic delivery of 5-fluorouracil through excised human stratum corneum.

    Science.gov (United States)

    Singh, B N; Jayaswal, S B

    2008-04-01

    The objective of this study was to determine the effects of ionization, current density and penetration enhancers on the iontophoretic delivery of 5-fluorouracil (5-FU) through excised human stratum corneum (HSC). The iontophoretic (cathodal) transport of 5-FU was assessed in vitro at three physiologically relevant pH values of 5.0, 7.4 and 8.0, at various levels of current density ranging between 0.15 to 0.98 mA/cm2, and in the presence of suitable penetration enhancers, namely Azone(®) (AZ), lauryl alcohol (LA), and isopropyl myristate (IPM). The steady-state flux at constant current density (0.47 mA/cm(2)) was increased by approximately 19, 10 and 27 fold at pH 5, 7.4 and 8.0, respectively. The effect of current density at pH 7.4 exhibited a linear correlation between current density and steady-state flux (r = 0.98, p = 0.002), which indicates the potential of iontophoresis for controlled transdermal delivery of 5-FU. The combination of cathodal iontophoresis with IPM produced an additive enhancement which may be attributed to aggravated skin perturbation effect and increased skin conductivity. Other enhancers such as AZ and LA produced negative or no further enhancement respectively, when used in conjunction with cathodal iontophoresis. It may be therefore concluded that pH and current density play critical role during iontophoretic delivery of 5-FU, and combination of a chemical penetration enhancer and iontophoresis can not be always viewed as a synergistic strategy which should be evaluated on a case-by-case basis for each drug candidate/enhancer combination.

  12. Measurement of Current Profile in a Tokamak Through AC Modulation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The plasma current is modulated with an alternating current (ac) component in a frequency range of 90 Hz~900 Hz in the plateau discharge phase in the CT-6B tokamak. A plasma electric conductivity profile in a form of (1 - r2/a2)α with a parameter α, which is fitted with the experimental data, can be determined. The effects of magnetic shear in a tokamak field configuration on the current penetration are taken into account in the numerical simulation. The measurement method and obtained results are discussed.

  13. Input current shaped ac-to-dc converters

    Science.gov (United States)

    1985-01-01

    Input current shaping techniques for ac-to-dc converters were investigated. Input frequencies much higher than normal, up to 20 kHz were emphasized. Several methods of shaping the input current waveform in ac-to-dc converters were reviewed. The simplest method is the LC filter following the rectifier. The next simplest method is the resistor emulation approach in which the inductor size is determined by the converter switching frequency and not by the line input frequency. Other methods require complicated switch drive algorithms to construct the input current waveshape. For a high-frequency line input, on the order of 20 kHz, the simple LC cannot be discarded so peremptorily, since the inductor size can be compared with that for the resistor emulation method. In fact, since a dc regulator will normally be required after the filter anyway, the total component count is almost the same as for the resistor emulation method, in which the filter is effectively incorporated into the regulator.

  14. Input-current shaped ac to dc converters

    Science.gov (United States)

    1986-01-01

    The problem of achieving near unity power factor while supplying power to a dc load from a single phase ac source of power is examined. Power processors for this application must perform three functions: input current shaping, energy storage, and output voltage regulation. The methods available for performing each of these three functions are reviewed. Input current shaping methods are either active or passive, with the active methods divided into buck-like and boost-like techniques. In addition to large reactances, energy storage methods include resonant filters, active filters, and active storage schemes. Fast voltage regulation can be achieved by post regulation or by supplementing the current shaping topology with an extra switch. Some indications of which methods are best suited for particular applications concludes the discussion.

  15. Iontophoretic Transport Across a Multiple Membrane System

    OpenAIRE

    Molokhia, Sarah A.; Zhang, Yanhui; Higuchi, William I.; Li, S. Kevin

    2008-01-01

    The objective of the present study was to investigate the iontophoretic transport behavior across multiple membranes of different barrier properties. Spectra/Por® (SP) and Ionac membranes were the synthetic membranes and sclera was the biomembrane in this model study. The barrier properties of SP membranes were determined individually in passive and iontophoresis transport experiments with tetraethylammonium ion (TEA), chloride ion (Cl), and mannitol as the model permeants. Passive and iontop...

  16. Alternating current(AC) corrosion analyzed by electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Tae Hyun; Kim, Dae Kyeong; Bae, Jeong Hyo; Lee, Hyun Goo; Lee, Sung Jin [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)

    2002-12-15

    So far, many research results on AC corrosion have been reported but each one is not consistent with another. In order to understand the characteristics and factors affecting on AC corrosion, Electrochemical impedance spectroscopy (E.I.S) was used and changes in kinetics and surface properties was analyzed. Generally, E.I.S. test has been used mainly for the diagnosis of the concrete corrosion and coating material. However, considering the outstanding functions of E.I.S. test, it can be adopted as a good method to study AC corrosion. Electrolyte resistance (R{sub sol}), double layer capacitance (C{sub dl}) and polarization resistance (R{sub p}) are the basic circuit elements. Using the model which is consist of these basic elements, various results of E.I.S. test can be interpreted. And through this method the mechanism and characteristics of AC corrosion can be explained

  17. Subcutaneous concentrations following topical iontophoretic delivery of diclofenac.

    Science.gov (United States)

    Kasha, P C; Anderson, C R; Morris, R L; Sembrowich, W L; Chaturvedula, A; Banga, A K

    2012-10-01

    A self-contained Wearable Electronic Disposable Drug Delivery (WEDD(®)) patch was used to demonstrate that diclofenac levels delivered by iontophoresis are greater than estimated minimal effective concentrations in local subcutaneous tissue and are also greater than either passive transdermal or intravenous delivery using hairless rats. In vitro iontophoretic delivery was evaluated to optimize donor cell formulation using Franz diffusion cells and 1000 NMWL Millipore ultrafiltration membrane. In vivo animal studies were done using patches powered with a 4-volt system, consisting of a 1-volt Zn anode and Ag/AgCl cathode with built in 3-volt lithium battery. Blood and microdialysis samples were collected at different time points after patch application. Current levels increased to 1.0 mA at 30 min, then fell to a steady state of ~ 0.4 mA. Both WEDD(®) and passive patches produced measurable levels of diclofenac in the subcutaneous tissue below the application site (C(max) ± SE = 113.3 ± 61.7 ng/mL and 36.3 ± 15.9 ng/mL, respectively). The dose delivered in six hours was calculated to be 0.226 ± 0.072 mg and 0.430 ± 0.048 mg in passive and iontophoretic delivery, respectively. Diclofenac was not detected in the subcutaneous tissue after intravenous administration of 1.5 mg/kg diclofenac solution. The trend indicates that WEDD(®) can be used to successfully deliver diclofenac to subcutaneous tissue to concentrations higher when compared to either passive delivery or intravenous dosing of 1.5 mg/kg.

  18. DC Vs AC - War Of Currents For Future Power Systems A HVDC Technology Overview

    Directory of Open Access Journals (Sweden)

    Anil K. Rai

    2015-08-01

    Full Text Available DC vs AC discussion began in 1880s with development of first commercial power transmission in Wall Street New York. Later when AC technology came into notice by efforts of inventor and researcher Sir Nicola Tesla soon the advantages of AC transmission and AC devices overtook the DC technology. It was hoped that DC technology had lost battle of currents. Today with researches going on FACTS devices and bulk power transmission HVDC has again gained a reputation in power sector. Solution of this centuries old debate is to develop HVDC systems that assists HVAC systems for better performance stability and control

  19. Mapping entrained brain oscillations during transcranial alternating current stimulation (tACS)

    NARCIS (Netherlands)

    Witkowski, M.; Garcia Cossio, E.; Chander, B.S.; Braun, C.; Birbaumer, N.; Robinson, S.E.; Soekadar, S.R.

    2016-01-01

    Transcranial alternating current stimulation (tACS), a non-invasive and well-tolerated form of electric brain stimulation, can influence perception, memory, as well as motor and cognitive function. While the exact underlying neurophysiological mechanisms are unknown, the effects of tACS are mainly

  20. AC losses in monofilamentary MgB{sub 2} round wire carrying alternating transport currents

    Energy Technology Data Exchange (ETDEWEB)

    Kajikawa, K [Research Institute of Superconductor Science and Systems, Kyushu University, Fukuoka 819-0395 (Japan); Kawano, T [Department of Electrical and Electronic Systems Engineering, Kyushu University, Fukuoka 819-0395 (Japan); Osaka, R [Department of Electrical Engineering, Kyushu University, Fukuoka 819-0395 (Japan); Nakamura, T [Department of Electrical Engineering, Kyoto University, Kyoto 615-8510 (Japan); Sugano, M [Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan); Takahashi, M; Wakuda, T, E-mail: kajikawa@sc.kyushu-u.ac.j [Hitachi Research Laboratory, Hitachi, Ltd, Hitachi 319-1292 (Japan)

    2010-04-15

    AC losses in a monofilamentary MgB{sub 2} round wire with niobium and copper metal sheaths and carrying alternating transport currents are evaluated at several temperatures and frequencies. First, the transport current losses are observed electrically using a lock-in amplifier. Experimental results show that the AC losses decrease with an increase in the temperature if the amplitude of the transport current normalized by the corresponding critical current is maintained constant. On the other hand, the AC losses increase slightly with the frequency. Next, the AC losses are calculated numerically by a finite difference method. The numerical results for the superconductor filament show a good agreement with the results of the conventional theoretical expression formulated using the Bean model over a wide range of current amplitudes. It is also found that the AC losses in the niobium sheath are negligible whereas those in the copper sheath are comparable with those in the superconductor. On the basis of the numerical calculations, an expression is analytically derived for estimating the eddy current loss occurring in a metal sheath. The derived expression well reproduces the AC loss properties of both the copper and niobium sheaths.

  1. AC losses in monofilamentary MgB2 round wire carrying alternating transport currents

    Science.gov (United States)

    Kajikawa, K.; Kawano, T.; Osaka, R.; Nakamura, T.; Sugano, M.; Takahashi, M.; Wakuda, T.

    2010-04-01

    AC losses in a monofilamentary MgB2 round wire with niobium and copper metal sheaths and carrying alternating transport currents are evaluated at several temperatures and frequencies. First, the transport current losses are observed electrically using a lock-in amplifier. Experimental results show that the AC losses decrease with an increase in the temperature if the amplitude of the transport current normalized by the corresponding critical current is maintained constant. On the other hand, the AC losses increase slightly with the frequency. Next, the AC losses are calculated numerically by a finite difference method. The numerical results for the superconductor filament show a good agreement with the results of the conventional theoretical expression formulated using the Bean model over a wide range of current amplitudes. It is also found that the AC losses in the niobium sheath are negligible whereas those in the copper sheath are comparable with those in the superconductor. On the basis of the numerical calculations, an expression is analytically derived for estimating the eddy current loss occurring in a metal sheath. The derived expression well reproduces the AC loss properties of both the copper and niobium sheaths.

  2. The Topological AC and HMW Effects, and the Dual Current in 2+1 Dimensions

    CERN Document Server

    He, X G; He, Xiao-Gang

    2001-01-01

    We study the Aharonov-Casher (AC) effect and the related He-McKellar-Wilkens (HMW) effect in 2+1 dimensions. In this restricted space these effects are the result of the interaction of the electromagnetic field tensor with the dual of a current. Transferring the dual operation from the current to the field tensor shows that %these effects are this interaction may be reinterpreted as due to the interaction of an effective vector potential and a current, and the AC and HMW effects follow immediately. A general proof of this for particles with an arbitrary spin is provided. The restriction to 2+1 dimensions, with this interpretation, provides a unified way of treating the AC and HMW effects for an arbitrary spin. Perhaps more interestingly the treatment shows that a spin-0 particle can show AC and HMW effects, although it has no magnetic or electric dipole moment in the usual sense.

  3. Frequency-dependent critical current and transport ac loss of superconductor strip and Roebel cable

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Kailash Prasad [Landcare Research, Palmerston North 4442 (New Zealand); Raj, Ashish [Computer Science in Radiology, Weill Medical College, Cornell University, NY 10022 (United States); Brandt, Ernst Helmut [Max-Planck-Institut fuer Metallforschung, PO B 800665, D-70506 Stuttgart (Germany); Kvitkovic, Jozef; Pamidi, Sastry V, E-mail: thakurk@landcareresearch.co.nz, E-mail: asr2004@med.cornell.edu, E-mail: ehb@mf.mpg.de, E-mail: kvitkovic@caps.fsu.edu, E-mail: pamidi@caps.fsu.edu [Center for Advanced Power System, Florida State University, Tallahassee, FL 32310 (United States)

    2011-06-15

    The frequency-dependent critical current of a superconductor strip and Roebel cable has been studied using a 2D finite element simulation. It is shown that the critical current of the superconductor increases with frequency as f{sup 1/n}, where n is the exponent of the power law flux creep model. Transport ac loss in a superconductor strip decreases with frequency as f{sup -2/n} when the amplitude of the applied ac current is far less than its critical current. However, when the applied current is large and becomes comparable to the critical current, the transport ac loss decreases with frequency as 1/f. The analytical results are substantiated with available experimental data and the results of a 2D finite element simulation.

  4. Finite element modelling of electric currents in AC submerged arc furnaces

    CSIR Research Space (South Africa)

    Mc Dougall, I

    2007-01-01

    Full Text Available . ANSYS/Multiphysics was used to predict the current density distribution in the electrodes, raw material, slag and molten metal as a result of the three phases AC current. The effect of the electrode immersion on the current path was studied...

  5. AC Loss of Ripple Current in Superconducting DC Power Transmission Cable

    Science.gov (United States)

    Yoshitomi, K.; Otabe, E. S.; Vyatkin, V. S.; Kiuchi, M.; Matsushita, T.; Hamabe, M.; Yamaguchi, S.; Inada, R.

    As a method of largely reducing the transmission loss in the electric power grid, superconducting direct current (DC) power transmission cable has been investigated. Using superconducting DC power transmission cables, large amounts of current and energy can be transferred compared to conventional copper cables. In this case, an alternating current (AC) is converted to DC and superposed AC which is known as ripple current, and the energy loss by the ripple current is generated. Therefore it is desired to estimate the energy loss density for the case of DC current and superposed AC current for a design of DC transmission cable system. In this study, the hysteresis loss for DC current of 2 kA rectified from 60 Hz alternating current is calculated using the Bean model, and coupling loss was also estimated. The diameter of the cable was 40 mm. The ripple currents generated by multi-pulse rectifiers, 6-pulse, 12-pulse, and 24-pulse were considered. It is found that the total AC loss including the hysteresis loss and the coupling loss is considerably smaller than the supposed heat loss of 0.5 W/m which is obtained with a newly developed cable.

  6. The effects of theta transcranial alternating current stimulation (tACS) on fluid intelligence.

    Science.gov (United States)

    Pahor, Anja; Jaušovec, Norbert

    2014-09-01

    The objective of the study was to explore the influence of transcranial alternating current stimulation (tACS) on resting brain activity and on measures of fluid intelligence. Theta tACS was applied to the left parietal and left frontal brain areas of healthy participants after which resting electroencephalogram (EEG) data was recorded. Following sham/active stimulation, the participants solved two tests of fluid intelligence while their EEG was recorded. The results showed that active theta tACS affected spectral power in theta and alpha frequency bands. In addition, active theta tACS improved performance on tests of fluid intelligence. This influence was more pronounced in the group of participants that received stimulation to the left parietal area than in the group of participants that received stimulation to the left frontal area. Left parietal tACS increased performance on the difficult test items of both tests (RAPM and PF&C) whereas left frontal tACS increased performance only on the easy test items of one test (RAPM). The observed behavioral tACS influences were also accompanied by changes in neuroelectric activity. The behavioral and neuroelectric data tentatively support the P-FIT neurobiological model of intelligence.

  7. Transcranial Alternating Current Stimulation (tACS) Enhances Mental Rotation Performance during and after Stimulation

    Science.gov (United States)

    Kasten, Florian H.; Herrmann, Christoph S.

    2017-01-01

    Transcranial alternating current stimulation (tACS) has been repeatedly demonstrated to modulate endogenous brain oscillations in a frequency specific manner. Thus, it is a promising tool to uncover causal relationships between brain oscillations and behavior or perception. While tACS has been shown to elicit a physiological aftereffect for up to 70 min, it remains unclear whether the effect can still be elicited if subjects perform a complex task interacting with the stimulated frequency band. In addition, it has not yet been investigated whether the aftereffect is behaviorally relevant. In the current experiment, participants performed a Shepard-like mental rotation task for 80 min. After 10 min of baseline measurement, participants received either 20 min of tACS at their individual alpha frequency (IAF) or sham stimulation (30 s tACS in the beginning of the stimulation period). Afterwards another 50 min of post-stimulation EEG were recorded. Task performance and EEG were acquired during the whole experiment. While there were no effects of tACS on reaction times or event-related-potentials (ERPs), results revealed an increase in mental rotation performance in the stimulation group as compared to sham both during and after stimulation. This was accompanied by increased ongoing alpha power and coherence as well as event-related-desynchronization (ERD) in the alpha band in the stimulation group. The current study demonstrates a behavioral and physiological aftereffect of tACS in parallel. This indicates that it is possible to elicit aftereffects of tACS during tasks interacting with the alpha band. Therefore, the tACS aftereffect is suitable to achieve an experimental manipulation. PMID:28197084

  8. BOLD signal effects of transcranial alternating current stimulation (tACS) in the alpha range: A concurrent tACS-fMRI study.

    Science.gov (United States)

    Vosskuhl, Johannes; Huster, René J; Herrmann, Christoph S

    2016-10-15

    Many studies have proven transcranial alternating current stimulation (tACS) to manipulate brain activity. Until now it is not known, however, how these manipulations in brain activity are represented in brain metabolism or how spatially specific these changes are. Alpha-tACS has been shown to enhance the amplitude of the individual alpha frequency (IAF) and a negative correlation between alpha amplitude and occipital BOLD signal was reported in numerous EEG/fMRI experiments. Thus, alpha-tACS was chosen to test the effects of tACS on the BOLD signal. A reduction thereof was expected during alpha-tACS which shows the spatial extent of tACS effects beyond modeling studies. Three groups of subjects were measured in an MRI scanner, receiving tACS at either their IAF (N=11), 1Hz (control; N=12) or sham (i.e., no stimulation - a second control; N=11) while responding to a visual vigilance task. Stimulation was administered in an interleaved pattern of tACS-on runs and tACS-free baseline periods. The BOLD signal was analyzed in response to tACS-onset during resting state and in response to seldom target stimuli. Alpha-tACS at 1.0mA reduced the task-related BOLD response to visual targets in the occipital cortex as compared to tACS-free baseline periods. The deactivation was strongest in an area where the BOLD signal was shown to correlate negatively with alpha amplitude. A direct effect of tACS on resting state BOLD signal levels could not be shown. Our findings suggest that tACS-related changes in BOLD activity occur only as a modulation of an existing BOLD response.

  9. Modeling AC ripple currents in HTS coated conductors by integral equations

    Science.gov (United States)

    Grilli, Francesco; Xu, Zhihan

    2016-12-01

    In several HTS applications, the superconducting tapes experience the simultaneous presence of DC and AC excitations. For example in high-current DC cables, where the transport current is not perfectly constant, but it exhibits some ripples at different frequencies introduced by the rectification process (AC-DC conversion). These ripples give rise to dissipation, whose magnitude and possible influence on the device's cooling requirements need to be evaluated. Here we report a study of the AC losses in a HTS coated conductor subjected to DC currents and AC ripples simultaneously. The modeling approach is based on an integral equation method for thin superconductors: the superconducting tape is modeled as a 1-D object with a non-linear resistivity, which includes the dependence of the critical current density Jc on the magnetic field. The model, implemented in a commercial finite-element program, runs very fast (the simulation of one AC cycle typically takes a few seconds on standard desktop workstation): this allows simulating a large number of cycles and estimating when the AC ripple losses stabilize to a constant value. The model is used to study the influence of the flux creep power index n on the stabilization speed and on the AC loss values, as well as the effect of using a field-dependent Jc instead of a constant one. The simulations confirm that the dissipation level should not be a practical concern in HTS DC cables. At the same time, however, they reveal a strong dependence of the results upon the power index n and the form of Jc , which spurs the question whether the power-law is the most suitable description of the superconductor's electrical behavior for this kind of analysis.

  10. AC losses in HTS coils for high-frequency and non-sinusoidal currents

    Science.gov (United States)

    de Bruyn, B. J. H.; Jansen, J. W.; Lomonova, E. A.

    2017-09-01

    AC losses in racetrack coils that are wound of YBCO tapes are measured for sinusoidal and non-sinusoidal transport currents with fundamental frequencies up to 1 kHz. An electrical method to measure losses for non-sinusoidal currents is developed for this purpose. The measured losses are compared to the losses calculated by 2D finite element models with power-law material models. The frequency and waveform-dependency of the measured losses are shown and compared to the results of the models over a wide range of frequencies and waveforms. Finally, it is shown that the finite element models can accurately predict AC losses resulting from non-sinusoidal transport currents as are present in highly dynamic motors with AC armature coils.

  11. AC LED的研究现状与发展%Current research and development of AC LED

    Institute of Scientific and Technical Information of China (English)

    满瑞; 李秋俊

    2012-01-01

    介绍了AC LED的特征及其工作原理,分析了AC LED相比于DC LED的优缺点,概述了AC LED在国内外的研究进展及其应用现状,讨论了AC LED技术发展过程中面临的挑战,并展望了其发展趋势.%The characteristics and operation principles of AC LED were presented.The advantages and disadvantages of AC LED compared with the DC LED were analyzed.The development and the latest application of AC LED were described.The challenges of the competition with the traditional light source were discussed,as well as the development trend of AC LED.

  12. ac current generation in chiral magnetic insulators and Skyrmion motion induced by the spin Seebeck effect.

    Science.gov (United States)

    Lin, Shi-Zeng; Batista, Cristian D; Reichhardt, Charles; Saxena, Avadh

    2014-05-09

    We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications.

  13. Passive and iontophoretic transport enhancement of insulin through porcine epidermis by depilatories: Permeability and fourier transform infrared spectroscopy studies

    OpenAIRE

    Rastogi, Sumeet K.; Singh, Jagdish

    2003-01-01

    The effect of thioglycolate-based depilatory lotions was studied on the in vitro passive and iontophoretic permeability of insulin through porcine epidermis and biophysical changes in the stratum corneum (SC) lipids and proteins. The porcine epidermis and Franz diffusion cells modified for iontophoresis were used for the in vitro transport studies. Cathodal iontophoresis was performed at 0.2 mA/cm2 current density. Resistance of the control- and depilatory-lotion-treated epidermis was determi...

  14. Investigation of the ex vivo and in vivo iontophoretic delivery of aceclofenac from topical gels in Albino rats

    OpenAIRE

    Bhatt, Bhavik; Koland, Marina; Shama, K Prasanna

    2013-01-01

    Introduction: Iontophoresis was used to enhance the delivery of aceclofenac (ACF) from topical gels formulated with various polymers for the purpose of relieving pain and inflammation. Materials and Methods Gels were formulated from hydroxypropyl methyl cellulose (HPMC), carbopol 934P, and sodium carboxymethyl cellulose (NaCMC). The formulations were evaluated for cathodal iontophoretic delivery of ACF through excised rat abdominal skin at three levels of current density of 0.5, 0.6 and 0.7 m...

  15. Compensation methods applied in current control schemes for large AC drive systems

    DEFF Research Database (Denmark)

    Rus, D. C.; Preda, N. S.; Teodorescu, Remus;

    2012-01-01

    The paper deals with modified PI current control structures for large AC drive systems which use surface mounted permanent magnet synchronous machines or squirrel-cage induction motors supplied with voltage source inverters. In order to reduce the power losses caused by high frequency switching...

  16. Calculation of AC loss in two-layer superconducting cable with equal currents in the layers

    Science.gov (United States)

    Erdogan, Muzaffer

    2016-12-01

    A new method for calculating AC loss of two-layer SC power transmission cables using the commercial software Comsol Multiphysics, relying on the approach of the equal partition of current between the layers is proposed. Applying the method to calculate the AC-loss in a cable composed of two coaxial cylindrical SC tubes, the results are in good agreement with the analytical ones of duoblock model. Applying the method to calculate the AC-losses of a cable composed of a cylindrical copper former, surrounded by two coaxial cylindrical layers of superconducting tapes embedded in an insulating medium with tape-on-tape and tape-on-gap configurations are compared. A good agreement between the duoblock model and the numerical results for the tape-on-gap cable is observed.

  17. The effects of bending strain on the critical current and AC loss of BSCCO/Ag tapes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guo Min [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Schwartz, Justin [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Sastry, P V P S S [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Lin Liangzhen [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080 (China); Xiao Liye [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080 (China); Yu Yunjia [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080 (China)

    2004-08-01

    When a coil or a winding is made, the superconducting tapes must be bent to different curvatures. Bending of high temperature superconducting (HTS) tapes can result in degradation of the critical current density and thus increase the AC losses of the tapes. Therefore, the effects of bending strain on the critical current and AC loss should be considered in the design of high temperature superconducting apparatus. In this paper, the dependence of critical current and AC loss on the bending diameter of the superconductor tape was experimentally investigated. The diameters of the curved tape were varied from 110 to 36 mm. AC loss measurements were taken at 77 K, 50 Hz. Analysis of the bending strain effects on the critical current and AC loss are presented. An expression describing the dependence of AC losses on bending strain is proposed by modifying Norris' formula. The experimental results are presented and compared with the calculated values.

  18. Effects of electrophoresis and electroosmosis during alternating current iontophoresis across human epidermal membrane.

    Science.gov (United States)

    Yan, Guang; Peck, Kendall D; Zhu, Honggang; Higuchi, William I; Li, S Kevin

    2005-03-01

    Previous studies in our laboratory have demonstrated that skin electrical resistance can be controlled by an alternating current (AC) electric field. By maintaining constant skin resistance, AC iontophoresis has been shown to reduce the iontophoretic flux variability of neutral permeants. Recently, it was found that symmetric square-wave AC could enhance iontophoretic transport of both neutral and ionic permeants by means of electrophoresis and/or electroosmosis in a synthetic membrane system, and a model was presented to describe the experimental results. The objective of the present study was to assess the effects of AC voltage and frequency and direct current (DC) offset on the flux of neutral and ionic model permeants with human epidermal membrane (HEM). Experiments were conducted under two different conditions: constant AC voltage iontophoresis and iontophoresis using constant HEM resistance with DC offset voltage. The following are the main findings in these experiments. In the constant AC voltage study, when the permeability data were compared at the same HEM electrical resistance, it was demonstrated that AC even at high frequency (approximately 1 kHz) could enhance the transport of the ionic permeant (tetraethylammonium ion) across HEM, but no enhancement was observed for the neutral permeant (arabinose). For the ionic permeant flux enhancement, the higher the applied AC voltage, the greater the flux enhancement. There was little or no AC frequency dependence of the flux enhancement in the frequency range of 50-1000 Hz. In the constant HEM resistance study of AC with DC offset, approximately linear relationships were observed between flux enhancement and the DC offset voltage for both the neutral and ionic permeants, and these results were found to be consistent with predictions of the modified Nernst-Planck model for conventional constant voltage DC iontophoresis. When the DC offset voltage was increased, the AC component of the flux enhancement for the

  19. Statistical evaluation of telephone noise interference caused by AC power line harmonic currents

    Energy Technology Data Exchange (ETDEWEB)

    Kuussaari, M. (Imatran Voima Oy, Vantaa (Finland))

    1993-04-01

    A statistical approach is applied for the evaluation of the limits for harmonic currents in AC power lines, the goal being to prevent excessive telephone noise interference voltages in subscriber cables in rural areas. The analysis is based on Monte-Carlo simulation which takes into account the effect of the experiental probability distributions of the relevant parameters. In the Finnish conditions, the properties of communication cables permit equivalent disturbing phase currents of 8 to 10 A. The digital exchanges permit approximately the same currents. Some new telephone types that have a low balance may make it necessary to limit the currents to a level that is somewhat lower.

  20. Modelling and analysis of current-programmed ac/dc converters

    Science.gov (United States)

    Tymerski, R. P. E.; Daly, K. C.

    1985-03-01

    Current-programmed dc/dc converters operating at a fixed switching frequency are analyzed using state-space averaged modeling. For converters operating in the continuous conduction mode, general closed form expressions that describe the dynamic ac small signal characteristics of the converter are obtained. A reduced order model is used to derive the control current input-to-output voltage, audio susceptibility and output impedance small signal ac transfer functions for the ideal buck, boost, and buck-boost converters operating in the continuous conduction model. It is shown that state-space averaging can correctly predict instability on the buck converter. Current-programmed converters operating in the discontinuous conduction mode are addressed, showing that the transfer functions are represented by a finite pole and a zero at infinity. Instability is predicted for the buck converter when an external ramp is omitted and the output-to-input voltage ratio is greater than or equal to two-thirds.

  1. DSP Based Control Implementation of an AC/DC Converter with Improved Input Current Distortion

    Directory of Open Access Journals (Sweden)

    WISUTMETHEEKORN, P.

    2011-05-01

    Full Text Available This paper presents a digital signal processor based control of an AC/DC converter with nearly unity power factor. Normally, the output voltage of a single-phase AC/DC converter comprises a voltage ripple with twice line-frequency. This affects the voltage control loop and leads to the converter input current distortion. The purposed method is designed to avoid the effect of the output voltage ripple. To verify the proposed control method, MATLAB/Simulink is used for system simulation. A hardware prototype is setup. A low cost digital signal processing chip dsPIC30F4011 is employed as a digital controller to control a CUK AC/DC converter. The converter specifications are 48V output voltage and 250W output power. From the simulation and the experimental results shown that the input current distortion of the purposed system is reduced and lower than the AC/DC converter that controlled by the conventional proportional-integral controller.

  2. Critical current density measurement of thin films by AC susceptibility based on the penetration parameter h

    Energy Technology Data Exchange (ETDEWEB)

    Li Xiaofen, E-mail: xiaofenli@gmail.com [Materials Research Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Grivel, Jean-Claude; Abrahamsen, Asger B.; Andersen, Niels H. [Materials Research Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)

    2012-07-15

    We have numerically proved that the dependence of AC susceptibility {chi} of a E(J) power law superconducting thin disc on many parameters can be reduced to one penetration parameter h, with E the electric field and J the current density. Based on this result, we propose a way of measuring the critical current density J{sub c} of superconducting thin films by AC susceptibility. Compared with the normally used method based on the peak of the imaginary part, our method uses a much larger range of the AC susceptibility curve, thus allowing determination of the temperature (T) dependence of J{sub c} from a normally applied {chi}(T) measurement. A fitting equation J{sub c} = 1.9H{sub a} Divides {chi} Prime Divides {sup 0.69}/d, -0.4 < {chi} Prime < -0.001 derived from the critical state case (Bean model) can be used in most situations, where H{sub a} is the amplitude of the applied AC field, {chi} Prime is the real part of the normalized susceptibility and d is the thickness of the film. The method is valid for the cases where the film is fully penetrated. We also discuss how the finite London penetration depth affects the susceptibility when the film is screened. Measurements with varying T, H{sub a} and DC background field H{sub dc} are performed to support the arguments.

  3. Critical current density measurement of thin films by AC susceptibility based on the penetration parameter h

    Science.gov (United States)

    Li, Xiao-Fen; Grivel, Jean-Claude; Abrahamsen, Asger B.; Andersen, Niels H.

    2012-07-01

    We have numerically proved that the dependence of AC susceptibility χ of a E(J) power law superconducting thin disc on many parameters can be reduced to one penetration parameter h, with E the electric field and J the current density. Based on this result, we propose a way of measuring the critical current density Jc of superconducting thin films by AC susceptibility. Compared with the normally used method based on the peak of the imaginary part, our method uses a much larger range of the AC susceptibility curve, thus allowing determination of the temperature (T) dependence of Jc from a normally applied χ(T) measurement. A fitting equation Jc = 1.9Ha∣χ‧∣0.69/d, -0.4 Bean model) can be used in most situations, where Ha is the amplitude of the applied AC field, χ‧ is the real part of the normalized susceptibility and d is the thickness of the film. The method is valid for the cases where the film is fully penetrated. We also discuss how the finite London penetration depth affects the susceptibility when the film is screened. Measurements with varying T, Ha and DC background field Hdc are performed to support the arguments.

  4. Controlled iontophoretic delivery of pramipexole: electrotransport kinetics in vitro and in vivo.

    Science.gov (United States)

    Kalaria, Dhaval R; Patel, Pratikkumar; Merino, Virginia; Patravale, Vandana B; Kalia, Yogeshvar N

    2014-09-01

    The objective of the study was to investigate the anodal iontophoretic delivery of pramipexole (PRAM), a dopamine agonist used for the treatment of Parkinson's disease, in order to determine whether therapeutic amounts of the drug could be delivered across the skin. Preliminary iontophoretic experiments were performed in vitro using porcine ear and human abdominal skin. These were followed by a pharmacokinetic study in male Wistar rats to determine the drug input rate in vivo. Stability studies revealed that after current application (0.5 mA/cm(2) for 6h), the solution concentration of PRAM was only 60.2 ± 5.3% of its initial value. However, inclusion of sodium metabisulfite (0.5%), an antioxidant, increased this to 97.2 ± 3.1%. Iontophoretic transport of PRAM across porcine skin in vitro was studied as a function of current density (0.15, 0.3, 0.5 mA/cm(2)) and concentration (10, 20, 40 mM). Increasing the current density from 0.15 to 0.3 and 0.5 mA/cm(2), resulted in 2.5- and 4-fold increases in cumulative permeation, from 309.5 ± 80.2 to 748.8 ± 148.1 and 1229.1 ± 138.6 μg/cm(2), respectively. Increasing the PRAM concentration in solution from 10 to 20 and 40 mM resulted in a 2-fold increase in cumulative permeation (816.4 ± 123.3, 1229.1 ± 138.6 and 1643.6 ± 201.3 μg/cm(2), respectively). Good linearity was observed between PRAM flux and both the applied current density (r(2)=0.98) and drug concentration in the formulation (r(2)=0.99). Co-iontophoresis of acetaminophen showed that electromigration was the dominant electrotransport mechanism (accounting for >80% of delivery) and that there was no inhibition of electroosmotic flow at any current density. Cumulative iontophoretic permeation across human and porcine skin (after 6h at 0.5 mA/cm(2)) was also shown to be statistically equivalent (1229.1 ± 138.6 and 1184.8 ± 236.4 μg/cm(2), respectively). High transport and delivery efficiencies were achieved for PRAM (up to 7% and 58%, respectively). The

  5. The effect of 10 Hz transcranial alternating current stimulation (tACS on corticomuscular coherence

    Directory of Open Access Journals (Sweden)

    Claudia eWach

    2013-08-01

    Full Text Available Synchronous oscillatory activity at alpha (8-12 Hz, beta (13-30 Hz, and gamma (30-90 Hz fre-quencies is assumed to play a key role for motor control. Corticomuscular coherence (CMC represents an established measure of the pyramidal system’s integrity. Transcranial alternating current stimulation (tACS offers the possibility to modulate ongoing oscillatory activity. Behaviourally, 20 Hz tACS in healthy subjects has been shown to result in movement slowing. However, the neurophysiological changes underlying these effects are not entirely understood yet. The present study aimed at ascertaining the effects of tACS at 10 and 20 Hz in healthy subjects on CMC and local power of the primary sensorimotor cortex. Neuromagnetic activity was recorded during isometric contraction before and at two time points (2-10 min and 30-38 min after tACS of the left primary motor cortex (M1, using a 306 channel whole head magnetoencephalo-graphy (MEG system. Additionally, electromyography (EMG of the right extensor digitorum communis (EDC muscle was measured. TACS was applied at 10 and 20 Hz, respectively, for 10 min at 1 mA. Sham stimulation served as control condition. The data suggest that 10 Hz tACS significantly reduced low gamma band CMC during isometric contraction. This implies that tACS does not necessarily cause effects at stimulation frequency. Rather, the findings suggest cross-frequency interplay between alpha and low gamma band activity modulating functional interaction between motor cortex and muscle.

  6. Effect of arc current on droplet ejection from tungsten-based electrode in multiphase AC arc

    Science.gov (United States)

    Hashizume, Taro; Tanaka, Manabu; Watanabe, Takayuki

    2017-05-01

    The dynamic behavior of droplet ejection from a tungsten electrode was successfully visualized using a high-speed camera and an appropriate band-pass filter. The effect of arc current on droplet ejection was investigated to understand the electrode erosion mechanism in the multiphase AC arc. The rate of erosion by droplet ejection increased with increasing current. This result was examined on the basis of the time variation in forces on a pending droplet at the electrode tip during the AC cycle. The relationship among electromagnetic force, surface tension, and ion pressure on the molten tip during the cathodic period is crucial for controling droplet ejection. The molten tip becomes hemispherical forming the pending droplet with an increase in the instantaneous value of arc current during the AC cycle. The pending droplet detaches from the electrode surface when electromagnetic force becomes the dominant force. Consequently, a higher rate of erosion by droplet ejection with a higher arc current resulted from a stronger electromagnetic force.

  7. 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 Finite-Element-Method (FEM) was used for the simulations of the effect of a changing current distribution during AC impedance spectrum recording on electroceramic point contact and thin film model electrodes. For pure electronic conducting point contact electrodes the transition from the prim......The Finite-Element-Method (FEM) was used for the simulations of the effect of a changing current distribution during AC impedance spectrum recording on electroceramic point contact and thin film model electrodes. For pure electronic conducting point contact electrodes the transition from...... 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...

  8. An Annotated Bibliography of High-Voltage Direct-Current Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993.

    Energy Technology Data Exchange (ETDEWEB)

    Litzenberger, Wayne; Lava, Val

    1994-08-01

    References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS).

  9. Mapping entrained brain oscillations during transcranial alternating current stimulation (tACS).

    Science.gov (United States)

    Witkowski, Matthias; Garcia-Cossio, Eliana; Chander, Bankim S; Braun, Christoph; Birbaumer, Niels; Robinson, Stephen E; Soekadar, Surjo R

    2016-10-15

    Transcranial alternating current stimulation (tACS), a non-invasive and well-tolerated form of electric brain stimulation, can influence perception, memory, as well as motor and cognitive function. While the exact underlying neurophysiological mechanisms are unknown, the effects of tACS are mainly attributed to frequency-specific entrainment of endogenous brain oscillations in brain areas close to the stimulation electrodes, and modulation of spike timing dependent plasticity reflected in gamma band oscillatory responses. tACS-related electromagnetic stimulator artifacts, however, impede investigation of these neurophysiological mechanisms. Here we introduce a novel approach combining amplitude-modulated tACS during whole-head magnetoencephalography (MEG) allowing for artifact-free source reconstruction and precise mapping of entrained brain oscillations underneath the stimulator electrodes. Using this approach, we show that reliable reconstruction of neuromagnetic low- and high-frequency oscillations including high gamma band activity in stimulated cortical areas is feasible opening a new window to unveil the mechanisms underlying the effects of stimulation protocols that entrain brain oscillatory activity.

  10. Modified technique of iontophoretic anesthesia for myringotomy in children.

    Science.gov (United States)

    Epley, J M

    1977-06-01

    A modified technique is described for iontophoretic anesthesia in children who require myringotomy and insertion of a tube (tympanostomy). Principal modifications include the following procedures: (1) preoperative parenteral sedation; (2) relatively painless injection of lidocaine hydrochloride-epinephrine hydrochloride solution into the external auditory canal skin after iontophoresis alone to eliminate the extreme bony canal wall tenderness; (3) injection of lidocaine-epinephrine solution into an atelectatic middle ear to anesthetize the promontory for painless tube insertion; (4) substitution of a disposable ECG electrode for a metal plate electrode to eliminate the possibility of electrical burn from metal-to-skin contact. These modifications enhance the effectiveness and the safety of iontophoretic anesthesia, minimize the need for general anesthesia, and liberalize the indications for tympanostomy.

  11. Iontophoretically enhanced ciclopirox delivery into and across human nail plate.

    Science.gov (United States)

    Hao, Jinsong; Smith, Kelly A; Li, S Kevin

    2009-10-01

    Transungual delivery of antifungal drugs is hindered by the low permeability of human nail plates, and as such, repeated dosing over a long period of time is necessary for effective treatment. The objectives of this study were to explore the possibilities of (a) enhancing the delivery of ciclopirox (CIC) across human nail plates and (b) sustaining CIC delivery from the larger resultant drug depot in the nail plates with constant voltage iontophoresis. In vitro passive and 9 V cathodal iontophoretic transport experiments of CIC across human nails were performed. Transungual CIC delivery with Penlac was the control. The amounts of CIC released from and deposited in the nails were determined in drug release and extraction experiments, respectively. Iontophoresis increased the flux of CIC permeated across the nail approximately 10 times compared to passive delivery from the same formulation or from Penlac. A significant amount of CIC was loaded into and released from the nails; the CIC concentrations were estimated to be above the minimum inhibitory concentrations of CIC for dermatophytic molds. The apparent transport lag time decreased in iontophoretic transport. The results demonstrate that iontophoresis was able to deliver an effective amount of CIC into and across the nails, and this suggests the feasibility of a constant voltage battery-powered transungual iontophoretic device.

  12. Analysis of the ac SQUID with low inductance and low critical current

    DEFF Research Database (Denmark)

    Sørensen, O. H.

    1976-01-01

    The properties of the ac SQUID magnetometer has been analyzed. The results are valid in the low-inductance low-critical-current regime, where the Lri0 producted is belowthe value at which the relation between the enclosed and externally applied magnetic dc flux becomes reentrant. The effects...... of the screening current circulating in the SQUID ring as well as of the SQUID-ring time constant, tau-Lr/R9 are taken into account. Here LR IS THE SQUID-ring inductance, and R is the shunt resistance in the shunted junction model assumed to describe the weak link. It is shown that for finite values of omegatau...

  13. Approach for Wide Use of Diagnostic Method for XLPE Cables Using Harmonics in AC Loss Current

    Science.gov (United States)

    Tsujimoto, Tomiyuki; Nakade, Masahiko; Yagi, Yukihiro; Ishii, Noboru

    Water tree is one of the degradation aspects of XLPE cables used for under-ground distribution or transmission lines. We have developed the loss current method using 3rd harmonic in AC loss current for cable diagnosis. Harmonic components in loss current arise as a result of the non-linear voltage-current characteristics of water trees. We confirmed that the 3rd harmonic in AC loss current had good correlation with water tree growth and break down strength. After that, we have applied this method to the actual 66kV XLPE cable lines. Up to now, the number of the application results is more than 130 lines. In case of cable lines terminated at gas-insulated switchgear (GIS), we have to remove the lightning arrestor (LA) and the potential transformer (PT) out of the test circuit. The reason is that we are afraid that each of LA and PT disturbs the degradation signal from cable lines. It takes extra time (1 or 2 days) and costs more to remove LA and PT in GIS out of a circuit. In order to achieve easy and reasonable diagnosis, we have developed a new method for cable lines terminated at GIS, by utilizing a technique, which enables to reduce signal of LA and PT from disturbed signal of cable lines. We confirmed the effect of the new method by experiments with actual cables.

  14. Experimental Study on the Influence of AC Stray Current on the Cathodic Protection of Buried Pipe

    Directory of Open Access Journals (Sweden)

    Qingmiao Ding

    2016-01-01

    Full Text Available The size of the damaged area of the coating and its position on the pipeline impacted the cathodic protection potential, and there was a damaged area of the greatest impact value. When damaged area was 300 mm2, the IR drop was the largest, and this situation could easily lead to inadequate protection; when the parallel spacing between pipeline and interference source was unchanged, the measured value curves of cathodic protection potential presented “U” shaped trend with the increasing stray current interference intensity. Under certain parallel spacing between pipeline and interference source, high alternating stray current intensity would cause serious negative offsets, so that the overprotection of the pipeline occurred, and make the coating crack; there was a parallel threshold length. When less than the threshold, the pipe-ground potential increases rapidly with the parallel length increasing. In order to judge whether a pipeline was interference by AC stray current and the risk of stray current corrosion, we should make a comprehensive analysis of the cathodic protection energizing potential, the switch-off potential, AC pipe-soil potential, IR drops, and so on.

  15. Mechanistic Studies of the Transdermal Iontophoretic Delivery of 5-OH-DPAT In Vitro

    NARCIS (Netherlands)

    Ackaert, Oliver W.; Van Smeden, Jeroen; De Graan, Jeroen; Dijkstra, Durk; Danhof, Meindert; Bouwstra, Joke A.

    2010-01-01

    A characterization and optimization of the in vitro transdermal iontophoretic transport of 5-hydroxy-2-(N,N,-di-n-propylamino)tetralin (5-OH-DPAT) is presented. The utility of acetaminophen as a marker of electroosmotic flow was studied as well. The following parameters of iontophoretic transport of

  16. Transdermal iontophoretic delivery of a novel series of dopamine agonists in vitro : physicochemical considerations

    NARCIS (Netherlands)

    Ackaert, Oliver W.; De Graan, Jeroen; Capancioni, Romano; Dijkstra, Durk; Danhof, Meindert; Bouwstra, Joke A.

    2010-01-01

    Objectives The transdermal iontophoretic delivery of a novel series of 2- aminotetralins and chromanamine-based dopamine agonists was investigated in corn. Methods Systematic structural modifications allowed us to investigate their effect on solubility in the donor phase and iontophoretic delivery a

  17. ac electrokinetic micropumps: The effect of geometrical confinement, Faradaic current injection, and nonlinear surface capacitance

    DEFF Research Database (Denmark)

    Olesen, Laurits Højgaard; Bruus, Henrik; Ajdari, A.

    2006-01-01

    Recent experiments have demonstrated that ac electrokinetic micropumps permit integrable, local, and fast pumping (velocities similar to mm/s) with low driving voltage of a few volts only. However, they also displayed many quantitative and qualitative discrepancies with existing theories. We...... therefore extend the latter theories to account for three experimentally relevant effects: (i) vertical confinement of the pumping channel, (ii) Faradaic currents from electrochemical reactions at the electrodes, and (iii) nonlinear surface capacitance of the Debye layer. We report here that these effects...... indeed affect the pump performance in a way that we can rationalize by physical arguments....

  18. Prediction of Pollution Flashover Voltage Based on Leakage Current Under AC Operating Voltage

    Institute of Scientific and Technical Information of China (English)

    MEI Hongwei; WANG Liming; GUAN Zhicheng; MAO Yingke

    2012-01-01

    This paper presented a model to predict the AC flashover voltage of contaminated suspension insulators.The prediction method is based on the maximum leakage current under AC operating voltage.Three kinds of widely used suspension insulators were tested in various contamination states such as pollution layers with different equivalent salt deposit density(ESDD),different composition of the conductive components,different non-soluble deposit density(NSDD) and different pollution distribution states to simulate the contamination states in nature.The effective ESDD was proposed and calculated.Influences of contamination states to maximum leakage current and flashover voltage were studied.Then,the relationships between flashover voltage and leakage current in these states were presented.Finally,considering the difference of insulator profiles,a new parameter is defined and a model to estimate the flashover voltage based on this parameter is developed.The model could be used in all kinds of suspension insulators in different contamination states and was validated by the test results.

  19. Critical current densities estimated from AC susceptibilities in proximity-induced superconducting matrix of multifilamentary wire

    Science.gov (United States)

    Akune, Tadahiro; Sakamoto, Nobuyoshi

    2009-03-01

    In a multifilamentary wire proximity-currents between filaments show a close resemblance with the inter-grain current in a high-Tc superconductor. The critical current densities of the proximity-induced superconducting matrix Jcm can be estimated from measured twist-pitch dependence of magnetization and have been shown to follow the well-known scaling law of the pinning strength. The grained Bean model is applied on the multifilamentary wire to obtain Jcm, where the filaments are immersed in the proximity-induced superconducting matrix. Difference of the superconducting characteristics of the filament, the matrix and the filament content factor give a variety of deformation on the AC susceptibility curves. The computed AC susceptibility curves of multifilamentary wires using the grained Bean model are favorably compared with the experimental results. The values of Jcm estimated from the susceptibilities using the grained Bean model are comparable to those estimated from measured twist-pitch dependence of magnetization. The applicability of the grained Bean model on the multifilamentary wire is discussed in detail.

  20. Critical current densities estimated from AC susceptibilities in proximity-induced superconducting matrix of multifilamentary wire

    Energy Technology Data Exchange (ETDEWEB)

    Akune, Tadahiro; Sakamoto, Nobuyoshi, E-mail: akune@te.kyusan-u.ac.j [Department of Electrical Engineering and Information Technology, Kyushu Sangyo University, 2-3-1 Matsukadai, Fukuoka 813-8503 (Japan)

    2009-03-01

    In a multifilamentary wire proximity-currents between filaments show a close resemblance with the inter-grain current in a high-T{sub c} superconductor. The critical current densities of the proximity-induced superconducting matrix J{sub cm} can be estimated from measured twist-pitch dependence of magnetization and have been shown to follow the well-known scaling law of the pinning strength. The grained Bean model is applied on the multifilamentary wire to obtain J{sub cm}, where the filaments are immersed in the proximity-induced superconducting matrix. Difference of the superconducting characteristics of the filament, the matrix and the filament content factor give a variety of deformation on the AC susceptibility curves. The computed AC susceptibility curves of multifilamentary wires using the grained Bean model are favorably compared with the experimental results. The values of J{sub cm} estimated from the susceptibilities using the grained Bean model are comparable to those estimated from measured twist-pitch dependence of magnetization. The applicability of the grained Bean model on the multifilamentary wire is discussed in detail.

  1. Measuring ac losses in superconducting cables using a resonant circuit:Resonant current experiment (RESCUE)

    DEFF Research Database (Denmark)

    Däumling, Manfred; Olsen, Søren Krüger; Rasmussen, Carsten;

    1998-01-01

    be recorded using, for example, a digital oscilloscope. The amplitude decay of the periodic voltage or current accurately reflects the power loss in the system. It consists of two components-an ohmic purely exponential one (from leads, contacts, etc.), and a nonexponential component originating from......A simple way to obtain true ac losses with a resonant circuit containing a superconductor, using the decay of the circuit current, is described. For the measurement a capacitor is short circuited with a superconducting cable. Energy in the circuit is provided by either charging up the capacitors...... with a certain voltage, or letting a de flow in the superconductor. When the oscillations are started-either by opening a switch in case a de is flowing or by closing a switch to connect the charged capacitors with the superconductor-the current (via a Rogowski coil) or the voltage on the capacitor can...

  2. Iontophoretic delivery of lisinopril: Optimization of process variables by Box-Behnken statistical design.

    Science.gov (United States)

    Gannu, Ramesh; Yamsani, Vamshi Vishnu; Palem, Chinna Reddy; Yamsani, Shravan Kumar; Yamsani, Madhusudan Rao

    2010-01-01

    The objective of the investigation was to optimize the iontophoresis process parameters of lisinopril (LSP) by 3 x 3 factorial design, Box-Behnken statistical design. LSP is an ideal candidate for iontophoretic delivery to avoid the incomplete absorption problem associated after its oral administration. Independent variables selected were current (X(1)), salt (sodium chloride) concentration (X(2)) and medium/pH (X(3)). The dependent variables studied were amount of LSP permeated in 4 h (Y(1): Q(4)), 24 h (Y(2): Q(24)) and lag time (Y(3)). Mathematical equations and response surface plots were used to relate the dependent and independent variables. The regression equation generated for the iontophoretic permeation was Y(1) = 1.98 + 1.23X(1) - 0.49X(2) + 0.025X(3) - 0.49X(1)X(2) + 0.040X(1)X(3) - 0.010X(2)X(3) + 0.58X(1)(2) - 0.17X(2)(2) - 0.18X(3)(2); Y(2) = 7.28 + 3.32X(1) - 1.52X(2) + 0.22X(3) - 1.30X(1)X(2) + 0.49X(1)X(3) - 0.090X(2)X(3) + 0.79X(1)(2) - 0.62X(2)(2) - 0.33X(3)(2) and Y(3) = 0.60 + 0.0038X(1) + 0.12X(2) - 0.011X(3) + 0.005X(1)X(2) - 0.018X(1)X(3) - 0.015X(2)X(3) - 0.00075X(1)(2) + 0.017X(2)(2) - 0.11X(3)(2). The statistical validity of the polynomials was established and optimized process parameters were selected by feasibility and grid search. Validation of the optimization study with 8 confirmatory runs indicated high degree of prognostic ability of response surface methodology. The use of Box-Behnken design approach helped in identifying the critical process parameters in the iontophoretic delivery of lisinopril.

  3. Effect of the combined action of Faradaic currents and mobility differences in ac electro-osmosis

    Science.gov (United States)

    González, A.; Ramos, A.; García-Sánchez, P.; Castellanos, A.

    2010-01-01

    In this work, we extend previous analyses of ac electro-osmosis to account for the combined action of two experimentally relevant effects: (i) Faradaic currents from electrochemical reactions at the electrodes and (ii) differences in ion mobilities of the electrolyte. In previous works, the ac electro-osmotic motion has been analyzed theoretically under the assumption that only forces in the diffuse (Debye) layer are relevant. Here, we first show that if the ion mobilities of a 1-1 aqueous solution are different, the charged zone expands from the Debye layer to include the diffusion layer. We later include the Faradaic currents and, as an attempt to explore both factors simultaneously, we perform a thin-layer, low-frequency, linear analysis of the system. Finally, the model is applied to the case of an electrolyte actuated by a traveling-wave signal. A steady liquid motion in opposite direction to the applied signal is predicted for some ranges of the parameters. This could serve as a partial explanation for the observed flow reversal in some experiments.

  4. Fractional Modeling of the AC Large-Signal Frequency Response in Magnetoresistive Current Sensors

    Directory of Open Access Journals (Sweden)

    Sergio Iván Ravelo Arias

    2013-12-01

    Full Text Available Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function  is obtained considering it as the relationship between sensor output voltage and input sensing current,[PLEASE CHECK FORMULA IN THE PDF]. The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR, giant magnetoresistance (GMR, spin-valve (GMR-SV and tunnel magnetoresistance (TMR. The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications.

  5. The AC (Alternating Current) Electrical Behavior of Multi-layered Thermoelectric Devices

    Science.gov (United States)

    Alim, Mohammad A.; Budak, Satilmis; Bhattacharjee, Sudip

    2016-11-01

    In this study the ac (alternating current) small-signal electrical data in the frequency range 5 Hz ≤ f ≤ 13 MHz are obtained for the multi-layered thermoelectric (TE) devices to extract underlying operative mechanisms via an equivalent circuit model. This model is developed from the complex plane plots in conjunction with the Bode plot. It is observed that the inductive behavior is prevalent for both unbombarded and bombarded TE devices regardless of the doses as both types are observed as somewhat weak in thermoelectric properties. The bombarded multi-layered devices followed a systematic pattern in ac behavior via semicircular relaxation both in the impedance and admittance planes for the same measured data. This pattern is attributed to the transition from one lumped behavior to two distinct mechanisms. It is observed that the conductive nature of the equivalent circuit model via non-blocking (non-capacitive) elements, attributed to the underlying operative electrical paths between the two opposite electrodes across the multi-layered device exists, satisfying direct current conditions of the equivalent circuit model. The inductive behavior at high frequencies originates from the conductive aspect of the lumped response of the device in addition to the contribution of the electrode leads. Thus, the proposed equivalent circuit model contains external inductance that verifies a meaningful representation of the multi-layered TE device, though weak in thermoelectric properties.

  6. Hysteresis Current Control Based Shunt Active Power Filter for Six Pulse Ac/Dc Converter

    Directory of Open Access Journals (Sweden)

    Rakesh Kumar Pandey

    2017-02-01

    Full Text Available In this paper the simulation of Shunt Active power Filter using P-Q theory and PI controller has been presented. This SAPF compensates the harmonic currents drawn by three phase six pulse AC/DC converter. The process of compensation is done by calculating the instantaneous reactive power losses using p-q theory and the PI controller to reduce the ripple voltage of the dc capacitor of the PWM-VSI. This approach is different from conventional approach and provides very effective solution. In this simulation we use hysteresis band current controller (HCC for switching the VSI inverter. The simulation has been done for both steady state and transient conditions

  7. Determination of the in vivo bioavailability of iontophoretically delivered diclofenac using a methyl nicotinate skin inflammation assay.

    Science.gov (United States)

    Lambrecht, Renzo; Clarys, Peter; Clijsen, Ron; Barel, André O

    2006-08-01

    In this study, we investigated the bioavailability of iontophoretically delivered diclofenac with the methylnicotinate (MN) test. The inhibition of an erythema provoked by MN is proportional to the bioavailability of diclofenac in the skin. It was our aim to use this procedure in the determination of the contribution of, respectively, passive diffusion, occlusion and electrically assisted delivery during an iontophoretic procedure as used in physiotherapy. A total of six application sites were marked on the volar forearms of each volunteer (n=12), for the following treatment and/or control modes: A=cathodal iontophoresis of 12 mg/cm(2) Voltaren Emulgel (diethylammonii diclofenac 1%) for 20 min; B=passive diffusion under a contact sponge; C=passive diffusion without any covering; D=current alone; E=standard MN response; and F=blanco site. Tristimulus surface colorimetry and Laser Doppler flowmetry were used to measure, respectively, the skin color and the perfusion of the microcirculation. Bioavailability was assessed by quantification of an MN-induced erythema under the different conditions. A significant reduction of the MN-induced erythema was observed with the Chromameter and Laser Doppler measurements for the following treatment modalities: (1) electrically assisted delivery: respectively, 65% and 100%, (2) application under a contact sponge: 66% and 97% and (3) passive diffusion without any covering: 32% and 65%. A significant reduction was equally observed for the site treated with the current alone: 19% and 42%. There was no significant difference between the response after iontophoretic-delivered diclofenac (mode A) and application of diclofenac under a contact sponge (mode B). The procedure used enabled us to evaluate the bioavailability of a non-steroidal anti-inflammatory drug in the skin. Under the conditions used, we did not find an increased bioavailability after electrically assisted delivery of diclofenac compared with the passive percutaneous

  8. Effect of microporation on passive and iontophoretic delivery of diclofenac sodium.

    Science.gov (United States)

    Patel, Hiren; Joshi, Abhay; Joshi, Amit; Stagni, Grazia

    2015-01-01

    Skin pretreatment with a microneedle roller (microporation (MP)) appears a simple and inexpensive technique to increase transdermal delivery of topically applied drug products. This study investigates the effect of MP on the passive and iontophoretic delivery of diclofenac (DCF) by quantifying dermis and plasma levels of DCF in a rabbit model. New Zealand albino female rabbits received either: (i) a topical application of 4 g of Voltaren® 1% gel with or without pretreatment with a microroller (0.5 mm needle length; density 23 microneedles per cm(2) area) or (ii) a DCF solution (40 mg/2.5 mL) via iontophoresis (IOMED transQ(E) medium size patch), with or without microroller pretreatment. A 300 µA/cm(2) cathodic current was applied for 20 min for a total of 80 mA. DCF concentrations were monitored in dermis with microdialysis sampling every 20 min for 5 h. Plasma samples were collected over the same period. In the passive delivery studies, microroller pretreatment increased Cmax by 1.5- and 2.0-fold in skin and plasma, respectively, and AUC by 1.5- and 2.4-fold in skin and plasma, respectively. In the iontophoresis delivery studies, microporation increased Cmax by 2.0-fold both in skin and in plasma, and AUC by 1.1- and 1.8-fold in skin and plasma, respectively. In conclusion, microneedle pretreatment increased significantly the systemic exposure of DCF from either passive or iontophoretic delivery, whereas the effect in skin was less pronounced.

  9. Experimental Investigations on PV Powered SVM-DTC Induction Motor without AC Phase Current Sensors

    Directory of Open Access Journals (Sweden)

    T. Muthamizhan

    2014-05-01

    Full Text Available The paper presents a low-cost, phase-current reconstruction algorithm for space vector modulated direct torque controlled induction motor using the information obtained from only one shunt resistor which is in series with low side switches in a conventional three-phase inverter. The aim is to develop a low-cost high - performance induction motor drive. It uses the dc-link voltage and dc current to reconstruct the stator currents needed to estimate the motor flux and the electromagnetic torque. Photovoltaic arrays convert solar power to dc electric power; uses chopper and dc-ac inverter to fed three phase Induction Motor. The chopper used here is current fed full bridge boost dc-dc converter, which is preferred and extensively used in high voltage applications and advantageous over voltage fed converters. The inverter switches are controlled by PWM techniques obtained from SVM-DTC of IM. The experimental investigations are given to prove the ability of the proposed scheme of reproducing the performances of a SVM- DTC IM drive.

  10. AC transport current loss in a coated superconductor in the Bean model

    Energy Technology Data Exchange (ETDEWEB)

    Carr, W.J. [LEI, 700 Technology Drive, Pittsburgh, PA 15219 (United States)]. E-mail: wjamescarrjr@att.net

    2004-10-15

    A new and straightforward calculation is made of the loss in a very thin superconducting strip of rectangular cross-section (e.g. the coating on a coated superconductor) carrying ac transport current in zero applied magnetic field, with a similar strip acting as the return path. The computation is made assuming only that the strip is composed of uniform material which obeys Maxwell's equations and the Bean model. An important consequence of the Bean model is the existence of a field-free region about the middle of the superconductor cross-section. The present loss calculation is novel in two respects: (1) It uses for the first time an actual computation of the shape of the field-free region rather than using qualitative assumptions, and (2) it uses a new approach for making the loss calculation, based on a rigorous solution of Maxwell's equations for this problem. The rigorous solution correctly treats the problem as three-dimensional, having a time-dependent charge on the surface of the superconductor, and having the electric field described by both a vector and a scalar potential. Loss computations are made for the ratio of peak current to critical current in the approximate range of one-half to one, where within this range the loss decreases by about two powers of 10. The most important result coming out of the present calculation (made for the case of a distant return path large compared with the conductor cross-section dimensions but small compared with the length of the conductor), is a confirmation of Norris's previously estimated loss expression which he obtained in a different way.

  11. DC current and AC impedance measurements on boron-doped single crystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Haitao; Gaudin, O.; Jackman, R.B. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Muret, P.; Gheeraert, E. [Laboratoire d' Etudes des Proprietes Electroniques des Solides, BP166, 38042 Grenoble Cedex 9 (France)

    2003-09-01

    In this paper, we report the first measurement of impedance on boron-doped single crystalline diamond films from 0.1 Hz to 10 MHz with the temperature ranging from -100 C up to 300 C. The Cole-Cole (Z' via Z{sup ''}) plots are well fitted to a RC parallel circuit model and the equivalent Resistance and Capacitance for the diamond films have been estimated using the Zview curve fitting. The results show only one single semicircle response at each temperature measured. It was found that the resistance decreases from 70 G{omega} at -100 C to 5 k{omega} at 300 C. The linear curve fitting from -100 C to 150 C shows the sample has an activation energy of 0.37 eV, which is consistent with the theoretical value published of this kind of material. The equivalent capacitance is maintained at the level of pF up to 300 C suggesting that no grain boundaries are being involved, as expected from a single crystal diamond. The activation energy from the dc current-temperature curves is 0.36 eV, which is consistent with the value from ac impedance. The potential of this under-used technique for diamond film analysis will be discussed. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Transdermal iontophoretic delivery of tacrine hydrochloride: Correlation between in vitro permeation and in vivo performance in rats.

    Science.gov (United States)

    Patel, Niketkumar; Jain, Shashank; Lin, Senshang

    2016-11-20

    The aim of present investigation is to evaluate the feasibility of transdermal iontophoretic delivery of tacrine hydrochloride in Sprague Dawley (SD) rats using anodal iontophoretic patches and to correlate plasma tacrine concentration profiles to in vitro tacrine permeation flux. In vitro skin permeation studies were carried out across artificial membrane CELGRAD(®) 2400, freshly excised SD rat abdominal skin, freshly excised hairless rat abdominal skin, and frozen pig skin to examine the role of permeation membranes. Furthermore, plasma profiles with an application of 0.1-0.3mA current strength and tacrine concentration loading of 5-20mg/ml were obtained in SD rats. The tacrine plasma profiles were fitted to one-compartmental model using WinNonlin and in vivo transdermal absorption rates were then correlated to in vitro permeation profiles using various approaches. Tacrine permeation across membranes revealed current dependent interspecies differences at lower current strength application which diminished at higher current strength application, whereas, no significant difference in tacrine permeation was observed across fresh and frozen SD rat skin under 0.2mA current application. In vivo studies confirmed current and concentration dependent tacrine plasma profiles with possible tacrine depot formation under the skin in-line with earlier in vitro results. Correlation of in vivo transdermal absorption rates to in vitro permeation profiles revealed higher in vitro permeation fluxes compare to in vivo transdermal absorption rates at varied combination of current strength and concentrations. Present in vivo studies support the earlier published in vitro findings and tacrine plasma profiles show a potential to reach therapeutic effective concentration of tacrine hydrochloride to provide a platform for pre-programmed tacrine delivery. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Synergistic iontophoretic drug delivery of risedronate sodium in combination with electroporation and chemical penetration enhancer: In-vitro and in-vivo evaluation

    Directory of Open Access Journals (Sweden)

    Swaroop R Lahoti

    2015-01-01

    Full Text Available In the present investigation iontophoretic permeation of risedronate sodium (RS through optimized gel based formulation was evaluated with respect to various electrical parameters like Current density and type of current. The study also involved enhancement the iontophoretic permeation of RS in combination with electroporation and chemical penetration enhancers with its in-vivo Pharmacokinetic evaluation. The permeation studies were carried through the human cadaver skin by using modified Franz diffusion cell and microcontroller based devices for iontophoresis and electroporation developed in the laboratory. In-vivo Pharmacokinetic studies were carried out in hairless rats. One way ANOVA followed by Tukey-Kramer test for multiple comparisons. The permeation of RS was significantly increased with iontophoresis at 0.5 mA/Cm 2 current density. The iontophoretic permeation was found depend on current density and ON:OFF ratio. The pulsatile current resulted in high permeation than continuous current. Maximum permeation was obtained at 0.5 mA/cm 2 with 1:1 pulsed current. When iontophoresis was coupled with chemical penetration enhancers and electroporation for 100 ms at 220V, synergistic enhancement in permeation was observed with shortened lag time and high flux. The required flux was achieved with area of application 1.55 cm 2 . In-vivo studies in hairless rats revealed high C max, low t max and increased area under the curve with electroporation, followed by iontophoresis indicated increased bioavailability. Relative bio-availability was 4.6 when calculated in comparison to passive studies.

  14. Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

    Science.gov (United States)

    Gallegos-Lopez, Gabriel; Nagashima, James M.; Perisic, Milun; Hiti, Silva

    2012-02-14

    A system is provided for controlling two AC machines. The system comprises a DC input voltage source that provides a DC input voltage, a voltage boost command control module (VBCCM), a five-phase PWM inverter module coupled to the two AC machines, and a boost converter coupled to the inverter module and the DC input voltage source. The boost converter is designed to supply a new DC input voltage to the inverter module having a value that is greater than or equal to a value of the DC input voltage. The VBCCM generates a boost command signal (BCS) based on modulation indexes from the two AC machines. The BCS controls the boost converter such that the boost converter generates the new DC input voltage in response to the BCS. When the two AC machines require additional voltage that exceeds the DC input voltage required to meet a combined target mechanical power required by the two AC machines, the BCS controls the boost converter to drive the new DC input voltage generated by the boost converter to a value greater than the DC input voltage.

  15. In vivo iontophoretic delivery of salmon calcitonin across microporated skin.

    Science.gov (United States)

    Vemulapalli, Viswatej; Bai, Yun; Kalluri, Haripriya; Herwadkar, Anushree; Kim, Hyun; Davis, Shawn P; Friden, Phil M; Banga, Ajay K

    2012-08-01

    The purpose of this study was to determine the effect of microneedle (MN) technology and its combination with iontophoresis (ITP) on the in vivo transdermal delivery of salmon calcitonin (sCT). Maltose MNs (500 µm) were used to porate skin prior to application of the drug, with or without ITP. Micropores created by maltose MNs were characterized by histological sectioning and calcein imaging studies, which indicated uniformity of the created micropores. In vivo studies were performed in hairless rats to assess the degree of enhancement achieved by ITP (0.2 mA/cm² for 1 h), MNs (81 MNs), and their combination. In vivo studies indicate a serum maximal concentration of 0.61 ± 0.42 ng/mL, 1.79 ± 0.72 ng/mL, and 5.51 ± 0.32 ng/mL for ITP, MNs, and combination treatment, respectively. MN treatment alone increased serum concentration 2.5-fold and the combination treatment increased the concentration ninefold as compared with iontophoretic treatment alone. Combination treatment of ITP and MNs resulted in the highest delivery of sCT and therapeutic levels were achieved within 5 min of administration.

  16. Fentanyl Iontophoretic Transdermal System: A Review in Acute Postoperative Pain.

    Science.gov (United States)

    Scott, Lesley J

    2016-04-01

    Fentanyl iontophoretic transdermal system (ITS) [Ionsys(®)] is indicated for the management of acute postoperative pain in adults requiring opioid analgesia in the hospital setting. This article reviews the clinical use of fentanyl ITS for postoperative pain management, and summarizes the pharmacology of fentanyl and the characteristics of the two-component fentanyl ITS (Ionsys(®)) device. In well-designed, multicentre clinical trials, fentanyl ITS was an effective and generally well tolerated method for managing acute postoperative pain in inpatients who had undergone major abdominal, thoracic or orthopaedic surgery. Overall, fentanyl ITS provided equivalent analgesic efficacy to that with morphine patient-controlled intravenous analgesia (PCIA), but was perceived to be more convenient/easier to use than morphine PCIA by patients, nurses and physical therapists. Patients receiving fentanyl ITS also had a greater ability to mobilize after surgery than patients receiving morphine PCIA. In addition, relative to morphine PCIA, fentanyl ITS offers advantages in terms of the noninvasive administrative route (i.e. transdermal needle-free administration), pre-programmed delivery (no risk of programming errors/incorrect dosing) and improved tolerability with regard to the overall incidence of opioid-related adverse events (ORAEs) and some individual ORAEs. Hence, fentanyl ITS is a useful option for the management of acute postoperative pain in adults requiring opioid analgesia in the hospital setting.

  17. Quasienergy spectrum and tunneling current in ac-driven triple quantum dot shuttles

    Energy Technology Data Exchange (ETDEWEB)

    Villavicencio, J [Facultad de Ciencias, Universidad Autonoma de Baja California, Ensenada (Mexico); Maldonado, I [Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (Mexico); Cota, E [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico, Ensenada (Mexico); Platero, G, E-mail: villavics@uabc.edu.mx [Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid (Spain)

    2011-02-15

    The dynamics of electrons in ac-driven double quantum dots have been extensively analyzed by means of Floquet theory. In these systems, coherent destruction of tunneling has been shown to occur for certain ac field parameters. In this work we analyze, by means of Floquet theory, the electron dynamics of a triple quantum dot in series attached to electric contacts, where the central dot position oscillates. In particular, we analyze the quasienergy spectrum of this ac-driven nanoelectromechanical system as a function of the intensity and frequency of the ac field and of external dc voltages. For strong driving fields, we derive, by means of perturbation theory, analytical expressions for the quasienergies of the driven oscillator system. From this analysis, we discuss the conditions for coherent destruction of tunneling (CDT) to occur as a function of detuning and field parameters. For zero detuning, and from the invariance of the Floquet Hamiltonian under a generalized parity transformation, we find analytical expressions describing the symmetry properties of the Fourier components of the Floquet states under such a transformation. By using these expressions, we show that in the vicinity of the CDT condition, the quasienergy spectrum exhibits exact crossings which can be characterized by the parity properties of the corresponding eigenvectors.

  18. Development of Harmonic-Noise Reduction Technology in Diagnostic Method using AC Loss Current for Water Treed XLPE Cable

    Science.gov (United States)

    Tsujimoto, Tomiyuki; Nakade, Masahiko; Yagi, Yukihiro; Ishii, Noboru

    Water tree is one of the degradation aspects of XLPE cables used for under-ground distribution or transmission lines. We have developed the loss current method using 3rd harmonic in AC loss current for cable diagnosis. Harmonic components in loss current arise as a result of the non-linear voltage-current characteristics of water trees. We confirmed that the 3rd harmonic in AC loss current had good correlation with water tree growth and break down strength. After that, we have applied this method to the actual 66kV XLPE cable lines. Up to now, the number of the application results is more than 120 lines. In this method, it is sometimes said that the degradation signal (3rd harmonic in loss current) is affected by the 3rd harmonic in the test voltage. To indicate and solve this problem, we investigated the extent of influence by 3rd harmonic in the test voltage, and found the rule of the influence. As a result, we developed a new technique of harmonic-noise reduction in loss current method that enabled a more highly accurate diagnosis and confirmed the effectiveness of this new technique by simulations and experiments with actual cables.

  19. Current distribution mapping in insulated (Gd,Y)BCO based stabilizer-free coated conductor after AC over-current test for R-SFCL application

    Science.gov (United States)

    Kar, Soumen; Li, Xiao-Fen; Selvamanickam, Venkat; Rao, V. V.

    2017-02-01

    Uniformity of critical current (Ic ) over long lengths of (GdY)-Ba-Cu-O ((Gd,Y)BCO)-based high temperature superconducting (HTS) tapes after long periods of AC current excitation is an important criterion in their selection for resistive type superconducting fault current limiter (R-SFCL). The present work describes such critical current (Ic ) uniformity measurements performed over 1m long, stabilizer-free (SF), 12 mm wide, 2nd generation (2G) (Gd,Y)BCO based HTS tape. A non-destructive method using a static hall probe (Tapestar®) with moving HTS tape configuration was employed for estimation of Ic uniformity. Scanning Hall probe microscopy (SHPM) was then used to examine the weak superconducting regions (i.e. less Ic ) with a static HTS tape. Remanent field distribution on the HTS tape was measured to yield the critical current density distribution. Except for small degradation of Ic at some locations, these studies confirmed near-uniform critical current distribution over meter-long (Gd,Y)BCO tapes, both in virgin state and after exposure to AC over current.

  20. Investigation of the effects of transcranial alternating current stimulation (tACS) on self-paced rhythmic movements.

    Science.gov (United States)

    Varlet, Manuel; Wade, Alanna; Novembre, Giacomo; Keller, Peter E

    2017-03-18

    Human rhythmic movements spontaneously entrain to external rhythmic stimuli. Such sensory-motor entrainment can attract movements to different tempi and enhance their efficiency, with potential clinical applications for motor rehabilitation. Here we investigate whether entrainment of self-paced rhythmic movements can be induced via transcranial alternating current stimulation (tACS), which uses alternating currents to entrain spontaneous brain oscillations at specific frequencies. Participants swung a handheld pendulum at their preferred tempo with the right hand while tACS was applied over their left or right primary motor cortex at frequencies equal to their preferred tempo (Experiment 1) or in the alpha (10Hz) and beta (20Hz) ranges (Experiment 2). Given that entrainment generally occurs only if the frequency difference between two rhythms is small, stimulations were delivered at frequencies equal to participants' preferred movement tempo (≈1Hz) and ±12.5% in Experiment 1, and at 10Hz and 20Hz, and ±12.5% in Experiment 2. The comparison of participants' movement frequency, amplitude, variability, and phase synchrony with and without tACS failed to reveal entrainment or movement modifications across the two experiments. However, significant differences in stimulation-related side effects reported by participants were found between the two experiments, with phosphenes and burning sensations principally occurring in Experiment 2, and metallic tastes reported marginally more often in Experiment 1. Although other stimulation protocols may be effective, our results suggest that rhythmic movements such as pendulum swinging or locomotion that are low in goal-directedness and/or strongly driven by peripheral and mechanical constraints may not be susceptible to modulation by tACS.

  1. Transdermal Iontophoretic Delivery of Atenolol in Combination with Penetration Enhancers: Optimization and Evaluation on Solution and Gels

    Directory of Open Access Journals (Sweden)

    Nandy B. C.

    2009-07-01

    Full Text Available In the present investigation, we prepared Atenolol (1.5 % w/w solution and various polymer formulations by incorporating the tween-20 or L-menthol, as a penetration enhancers and its effect on permeation of the drug through the excised abdominal rat skin were used to examined by using the vertical Franz-type diffusion cell. The physicochemical interactions between Atenolol and various polymers were investigated by performing the assay, ultra violet absorption maxima, Fourier transform infrared spectroscopy and it was further confirmed by thin layer chromatography studies, from which drug did not show any evidence of interaction with the polymers. We found that, L-menthol was superior than tween-20 to iontophoresis [current density applied 0.5 mA/cm2 and 90:10 (on: off ratio], in enhancing the transdermal permeation of Atenolol; it enhanced the flux of Atenolol by more than 2-folds, comparison to the preparations without penetration enhancer via passive diffusion, and 3 folds increased using iontophoresis alone with a shorter lag time. Atenolol also showed good stability in gel formulations. The basic parameters like % loading dose released at the end of the study, permeation coefficient and steady state flux (Jss were calculated and showed statistically significant difference (p<0.05. The results indicated that suitable iontophoretic delivery with desired permeability could be appeared and the cumulative amount-time curves were suitable to fit by a zero order equations which indicated a steady state permeation rate or sustained effect could be achieved from hydrogel; when it is combined with penetration enhancer, L-menthol. The results demonstrate that the semisolid gel formulations are more applicable than solution as a transdermal iontophoretic delivery system to administer clinically. Electrically assisted transdermal delivery of Atenolol significantly increased transport compared to passive delivery. Also, rapid and modulated delivery was

  2. Directed Current Induced by an Symmetrically ac Force Coexisting with a Time-Delayed Feedback

    Institute of Scientific and Technical Information of China (English)

    易述婷; 宋晖; 欧志娥; 艾保全; 熊建文

    2012-01-01

    We study the transport of overdamped Brownian particles in a symmetricaJly periodic potential in the presence of an asymmetrically ac driving force and a time-delayed feedback. It is found that for low frequencies, the average velocity can be negative by changing the driving amplitude, for high frequencies, there exists an optimized driving amplitude at which the average velocity takes its maximum value. Additionally, there is a threshold value of driving amplitude below which no directed transport can be obtained for high frequencies. For the large value of the delay time, the average velocity is independent of the delay time.

  3. Finite element model predicts current density distribution for clinical applications of tDCS and tACS

    Directory of Open Access Journals (Sweden)

    Toralf eNeuling

    2012-09-01

    Full Text Available Transcranial direct current stimulation (tDCS has been applied in numerous scientific studies over the past decade. However, the possibility to apply tDCS in therapy of neuropsychiatric disorders is still debated. While transcranial magnetic stimulation (TMS has been approved for treatment of major depression in the United States by the Food and Drug Administration (FDA, tDCS is not as widely accepted. One of the criticisms against tDCS is the lack of spatial specificity. Focality is limited by the electrode size (35 cm2 are commonly used and the bipolar arrangement. However, a current flow through the head directly from anode to cathode is an outdated view. Finite element (FE models have recently been used to predict the exact current flow during tDCS. These simulations have demonstrated that the current flow depends on tissue shape and conductivity. Toface the challenge to predict the location, magnitude and direction of the current flow induced by tDCS and transcranial alternating current stimulation (tACS, we used a refined realistic FE modeling approach. With respect to the literature on clinical tDCS and tACS, we analyzed two common setups for the location of the stimulation electrodes which target the frontal lobe and the occipital lobe, respectively. We compared lateral and medial electrode configuration with regard to theirusability. We were able to demonstrate that the lateral configurations yielded more focused stimulation areas as well as higher current intensities in the target areas. The high resolution of our simulation allows one to combine the modeled current flow with the knowledge of neuronal orientation to predict the consequences of tDCS and tACS. Our results not only offer a basis for a deeper understanding of the stimulation sites currently in use for clinical applications but also offer a better interpretation of observed effects.

  4. Transdermal iontophoretic delivery of apomorphine in patients improved by surfactant formulation pretreatment

    NARCIS (Netherlands)

    Li, GL; de Vries, Joeke; van Steeg, TJ; van den Busche, H; Maas, HJ; Reeuwijk, HJEM; Danhof, M; Bouwstra, JA; van Laar, T

    2005-01-01

    The objective of the present study is to evaluate the efficacy and the safety of transdermal iontophoretic delivery of Rapomorphine, a potent dopamine agonist, in combination with surfactant pretreatment in patients with advanced Parkinson's disease. Iontophoresis patches were applied in 16 patients

  5. AC current driven dynamic vortex state in YBa{sub 2}Cu{sub 3}O{sub 7-x}

    Energy Technology Data Exchange (ETDEWEB)

    Lucarelli, A.; Frey, A.; Yang, R.; Luepke, G. [The College of William and Mary, Department of Applied Science, Williamsburg, VA (United States); Grilli, F. [Los Alamos National Laboratory, Superconductivity Technology Center, Los Alamos, NM (United States); Haugan, T.; Levin, G.; Barnes, P. [Air Force Research Laboratory, Wright-Patterson AFB, OH (United States)

    2007-09-15

    Time-resolved magneto-optical imaging measurements show that an ac current enables the vortex matter in YBa{sub 2}Cu{sub 3}O{sub 7-x} thin films to reorganize into two coexisting steady states of driven vortex motion with different characteristics: a quasi-static disordered glassy state in the sample interior and a dynamic state of plastic motion near the edges. Finite-element calculations consistent with the critical state model show good agreement with the measured field profiles in the quasi-static state but predict a larger hysteretic behavior in the dynamic state. (orig.)

  6. Progress in research of iontophoretic delivery systems%离子电渗给药技术的研究进展

    Institute of Scientific and Technical Information of China (English)

    李丁; 程志红; 吴闻哲

    2011-01-01

    Iontophoresis as a non-invasive technique has been investigated for many years. Significant achievements have been made in the understanding of mechanisms underlying iontophoresis, which have contributed to the rational development of iontophoretic delivery systems. The application of a small electric current has enhanced the transport of charged, polar, and neutral compounds across the body. The principal distinguishing feature is the control afforded by iontophoresis and the ability to individualize therapies. This may become significant impact on interindividual variations in protein expression, and may be beneficial to drug metabolism and improvement of drug efficacy. This review focused on the progress in research of iontophoretic delivery systems, factors influencing iontophoretic process, new administration routes and conjunction with other enhancing technologies.%离子电渗技术作为一种非侵袭性给药方法已经研究了很多年,其作用机制已经广为人们所熟知并以此推动离子电渗给药系统的发展.该技术利用微量电流帮助解离、极性和中性药物分子透过机体屏障.它能够根据患者的自身情况调整治疗方案,这可以减少治疗时蛋白类药物的个体差异,影响药物代谢,进而提高治疗效果.本文综述了近年来离子电渗给药技术的研究进展、影响因素、新的给药途径以及与其他促渗技术的联合应用.

  7. Topical iontophoretic delivery of ionizable, biolabile aciclovir prodrugs: A rational approach to improve cutaneous bioavailability.

    Science.gov (United States)

    Chen, Yong; Alberti, Ingo; Kalia, Yogeshvar N

    2016-02-01

    The objective was to investigate the topical iontophoretic delivery of a series of amino acid ester prodrugs of aciclovir (ACV-X, where ACV=aciclovir and X=Arg, Gly, Ile, Phe, Trp and Val) as a means to enhance cutaneous delivery of ACV. The newly synthesized prodrugs were characterized by (1)H NMR and high resolution mass spectrometry. Analytical methods using HPLC-UV were developed for their quantification and each method was validated. Investigation of solution stability as a function of pH showed that all ACV-X prodrugs were relatively stable in acid conditions at pH 2.0 and pH 5.5 for up to 8h but susceptible to extensive hydrolysis at pH 7.4 and under alkaline conditions (pH 10). No ACV-X hydrolysis was observed after contact for 2h with the external surface of porcine stratum corneum. However, there was significant hydrolysis following contact with the dermal surface of dermatomed porcine skin, in particular, for ACV-Arg. Passive transport of ACV and ACV-X prodrugs from aqueous solution after 2h was below the limit of detection. Iontophoresis of ACV at 0.5 mA/cm(2) for 2h led to modest ACV skin deposition (QDEP,ACV) of 4.6 ± 0.3 nmol/cm(2). In contrast, iontophoresis of ACV-X prodrugs under the same conditions produced order of magnitude increases in cutaneous deposition of ACV species, that is, QDEP,TOTAL=QDEP,ACV+QDEP,ACV-X. QDEP,TOTAL for ACV-Gly, ACV-Val, ACV-Ile, ACV-Phe, ACV-Trp and ACV-Arg was 412.8 ± 44.0, 358.8 ± 66.8, 434.1 ± 68.2, 249.8 ± 81.4, 156.1 ± 76.3, 785.9 ± 78.1 nmol/cm(2), respectively. The extent of bioconversion of ACV-X to ACV in the skin was high and the proportion of ACV present ranged from 81% to 100%. The skin retention ratio, a measure of the selectivity of ACV species for deposition over permeation after iontophoretic delivery of ACV-X prodrugs, was dependent on both the rate of transport and the susceptibility to hydrolysis of the prodrugs. Skin deposition of ACV and its six prodrugs were investigated further as a

  8. The Space Charge Effect on the Discharge Current in Cross-Linked Polyethylene under High AC Voltages

    Science.gov (United States)

    Kwon, Yoon-Hyeok; Hwangbo, Seung; Lee, June-Ho; Yi, Dong-Young; Han, Min-Koo

    2003-12-01

    The space charge distributions in solid dielectrics have been usually investigated by means of the pulsed electroacoustic (PEA) method. However, most previous studies have been limited to the phenomenological analysis under DC voltages. In our study, the space charge distribution in cross-linked polyethylene (XLPE) has been measured using AC voltages by means of the modified PEA method. Simultaneously, the streamer discharges in an air gap have been measured in order to investigate the relationship between space charge and discharge current, and the relationship has been adapted to the case of dielectric barrier discharge. At high AC voltages, discharge current increases to the critical point, but no further increase is exhibited over the critical voltage and the discharge pattern is resolved by the space charge. This result indicates that the frequency effect and space charge characteristics of dielectric materials are preferred to the voltage effect in the adaptation to dielectric barrier discharge. The results well explain the space charge effect on partial discharge and the dielectric barrier discharge phenomenon.

  9. MEMS electrostatic inductive transformer using potassium ion electrets for up- or down-conversion of AC current

    Science.gov (United States)

    Suzuki, Masato; Moriyama, Takashi; Toshiyoshi, Hiroshi; Hashiguchi, Gen

    2016-10-01

    In this paper, we report on a novel MEMS electrostatic inductive transformer using potassium ion electrets on mechanically movable silicon microelectrodes. The device consists of a pair of electrostatic comb drive actuators that share a common mass in the middle part of a spring-mass-spring system. When an excitation AC voltage is applied to the electrode of the input-port comb drive at its mechanical resonant frequency, the mass in the middle oscillates to generate electrostatic inductive charges on the electrodes of the output-port comb drive, which could be read out as an output current. By appropriately designing the ratio of force factors of input- and output-port comb drives, the device operates as a transformer to amplify the current at a high efficiency over of 90% under the optimal load condition.

  10. Quench behavior of Sr0.6K0.4Fe2As2/Ag tapes with AC and DC transport currents at different temperature

    Science.gov (United States)

    Liu, Qi; Zhang, Guomin; Yang, Hua; Li, Zhenming; Liu, Wei; Jing, Liwei; Yu, Hui; Liu, Guole

    2016-09-01

    In applications, superconducting wires may carry AC or DC transport current. Thus, it is important to understand the behavior of normal zone propagation in conductors and magnets under different current conditions in order to develop an effective quench protection system. In this paper, quench behavior of Ag sheathed Sr0.6K0.4Fe2As2 (Sr-122 in the family of iron-based superconductor) tapes with AC and DC transport current is reported. The measurements are performed as a function of different temperature (20 K-30 K), varying transport current and operating frequency (50 Hz-250 Hz). The focus of the research is the minimum quench energy (MQE), the normal zone propagation velocity (NZPV) and the comparison of the related results with AC and DC transport current.

  11. Characterization of plasma electrolytic oxidation coatings on Zircaloy-4 formed in different electrolytes with AC current regime

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Yingliang, E-mail: chengyingliang@hnu.edu.cn [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Matykina, Enzhe [Dpt. Ciencia de los Materiales e Ingenieria Metalurgica, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, Madrid 28040 (Spain); Skeldon, Peter; Thompson, George [Corrosion and Protection Centre, School of Materials, University of Manchester, Sackville Street, Manchester M13 9PL (United Kingdom)

    2011-10-01

    Highlights: > ZrO{sub 2} coatings are grown on Zircaloy-4 by AC plasma electrolytic oxidation. > Tetragonal and monoclinic ZrO{sub 2} are formed using silicate electrolyte. > Pyrophosphate electrolyte results in flawed coatings of monoclinic ZrO{sub 2}. > Silicate favours formation of tetragonal ZrO{sub 2}, with coating hardness {approx}8 GPa. > Microstructures are related to temperature gradients and solidification rates. - Abstract: Plasma electrolytic oxidation was undertaken on Zircaloy-4 in alkaline silicate and pyrophosphate electrolytes, with a square waveform AC current regime. The resultant coatings were examined using scanning electron spectroscopy, X-ray diffraction and nanoindentation. The coatings formed in silicate electrolyte comprised mainly a porous inner layer and a more compact outer layer, with characteristic solidification structures being evident following prolonged treatment. The coatings contained monoclinic and tetragonal ZrO{sub 2}, the latter being mainly present in the outer layer, which was of hardness up to {approx}8 GPa. In contrast, extensively cracked coatings resulted from use of pyrophosphate electrolyte; the coating integrity was improved by the addition of silicate to the pyrophosphate electrolyte. The different morphologies of the coatings appeared to be related to the differing nature of the microdischarges and to the incorporation of silicon species that enhanced the formation of t-ZrO{sub 2}.

  12. Comparative study between an alternating current (AC) and a direct current (DC) electrification of an urban railway

    OpenAIRE

    Garriga Turu, Jordi

    2015-01-01

    This study will evaluate technically, energetic and economically the traction electrification network of the line Barcelona – Vallès operated by Ferrocarrils de la Generalitat de Catalunya (FGC) in the existing voltage system (1500 Vdc) and a new electrification under alternative current (25 kVac) will be proposed to be as well studied. The results obtained will be compared in order to obtain decision factors on which system best fits.

  13. Complex state variable- and disturbance observer-based current controllers for AC drives

    DEFF Research Database (Denmark)

    Dal, Mehmet; Teodorescu, Remus; Blaabjerg, Frede

    2013-01-01

    , extracted by a disturbance observer and then injected into the current controller. In this study, a revised version of a disturbance observer-based controller and a well known complex variable model-based design with a single set of complex pole are compared in terms of design aspects and performance...... of the parameter and the cross-coupling effect. Moreover, it provides a better performance, smooth and low noisy operation with respect to the complex variable controller....... of the stator current. In order to improve the current control performance an alternative current control strategy was proposed previously aiming to avoid the undesired cross-coupling and non-linearities between the state variables. These effects are assumed as disturbances arisen in the closed-loop path...

  14. Virtual Impedance Based Fault Current Limiters for Inverter Dominated AC Microgrids

    DEFF Research Database (Denmark)

    Lu, Xiaonan; Wang, Jianhui; Guerrero, Josep M.

    2017-01-01

    In this paper, a virtual impedance based fault current limiter (VI-FCL) is proposed for islanded microgrids comprised of multiple inverter interfaced distributed generators (DGs). Considering the increased fault current capability induced by high penetration of renewable energy sources (RESs), FC......, and the stability analysis in consideration of VI-FCLs is thereby studied. MATLAB/Simulink model comprised of three inverter-interfaced DGs is implemented to verify the feasibility of the proposed method....

  15. AC over-current characteristics of YBCO coated conductor with copper stabilizer layer considering insulation layer

    Science.gov (United States)

    Du, H.-I.; Kim, M.-J.; Kim, Y.-J.; Lee, D.-H.; Han, B.-S.; Song, S.-S.

    2010-11-01

    Compared with the first-generation BSCCO wire, the YBCO thin-film wire boasts low material costs and high Jc and superior magnetic-field properties, among other strengths. Meanwhile, the previous BSCCO wire material for superconducting cables has been researched on considerably with regard to its post-wire quenching characteristics during the application of an alternating over-current. In this regard, the promising YBCO thin-film wire has yet to be further researched on. Moreover, still lacking is research on the YBCO thin-film wire with insulating layers, which is essential in the manufacture of superconducting cables, along with the testing of the application of an alternating over-current to the wire. In this study, YBCO thin-film wires with copper-stabilizing layers were used in testing alternating over-current application according to the presence or absence of insulating layers and to the thickness of such layers, to examine the post-quenching wire resistance increase and quenching trends. The YBCO thin-film wire with copper-stabilizing layers has a critical temperature of 90 K and a critical current of 85 A rms. Moreover, its current application cycle is 5.5 cycles, and its applied currents are 354, 517, 712, and 915 A peak. These figures enabled the YBCO thin-film wires with copper-stabilizing layers to reach 90, 180, 250, and 300 K, respectively, in this study. These temperatures serve as a relative reference to examine the post-quenching wire properties following the application of an alternating over-current.

  16. A nontrivial factor in determining current distribution in an ac HTS cable-proximity effect

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A superconductor has zero resistance at the superconducting state. This unique property creates many exceptional phenomena, of which some are known and the others are not. Our experiments with multilayer high temperature superconductor (HTS) cable samples revealed a new phenomenon that alternating current had a tendency to flow in the inner and outer layers of the cables. We attribute the cause of this phenomenon to the electromagnetic interaction in an infinite electrical conductivity medium and term it "super-proximity-effect". This effect will greatly affect the performance of a multilayer superconducting cable and other superconducting devices which are involved with alternating current transportation.

  17. Online fault location on AC cables in underground transmission systems using screen currents

    DEFF Research Database (Denmark)

    Jensen, Christian Flytkjær; Nanayakkara, O.M.K.K; Rajapakse, Athula

    This paper studies online travelling wave methods for fault location on a crossbonded cable system using screen currents. During the construction of the electrical connection to the 400 MW off shore wind farm Anholt, it was possible to perform measurements on a 38.4 km crossbonded cable system...... coils if the screen currents contain the necessary information for accurate fault location. In this paper, this is examined by analysis of field measurements and through a study of simulations. The wavelet transform and visual inspection methods are used and the accuracy is compared. Field measurements...... and simulations are compared for testing the reliability of using simulations for studying fault location methods....

  18. Hysteresis losses in MgB2 superconductors exposed to combinations of low AC and high DC magnetic fields and transport currents

    DEFF Research Database (Denmark)

    Magnusson, N.; Abrahamsen, Asger Bech; Liu, Dawei

    2014-01-01

    a simplified theoretical treatment of the hysteresis losses based on available models in the literature with the aim of setting the basis for estimation of the allowable magnetic fields and current ripples in superconducting generator coils intended for large wind turbine direct drive generators. The resulting...... equations use the DC in-field critical current, the geometry of the superconductor and the magnitude of the AC magnetic field component as parameters. This simplified approach can be valuable in the design of MgB2 DC coils in the 1–4T range with low AC magnetic field and current ripples....

  19. Angular dependence of direct current decay in a closed YBCO double-pancake coil under external AC magnetic field and reduction by magnetic shielding

    Science.gov (United States)

    Geng, J.; Zhang, H.; Li, C.; Zhang, X.; Shen, B.; Coombs, T. A.

    2017-03-01

    High T c superconducting (HTS) coils are ideal candidates in the use of high field magnets. HTS coils carrying a direct current, however, suffer a non-negligible loss when they are exposed to an external AC magnetic field. Although this phenomenon is well known, no study concerning AC magnetic field angular dependence of direct current decay has ever been shown. In this work, we experimentally investigate the direct current decay characteristics in a closed double pancake coil made of a YBCO coated conductor under external AC field. AC field of different angles with respect to the coil plane is applied. Results show that the current decay rate presents a strong angular dependence. The fastest decay occurs when the field is parallel to the coil plane, in which case the surface of the tape in the outermost layer experiences most flux variation. To reduce the decay rate, we propose wrapping superconducting tapes around the outermost layer of the coil to shield external AC field. This method significantly reduces direct current decay rate under parallel field, without affecting the perpendicular self-field of the coil.

  20. Online Fault Location on AC Cables in Underground Transmission Systems using Sheath Currents

    DEFF Research Database (Denmark)

    Jensen, Christian Flytkjær; Nanayakkarab, Kasun; Rajapakse, Athula

    2014-01-01

    This paper studies online travelling wave methods for fault location on a crossbonded cable system using sheath currents. During the construction of the electrical connection to the 400 MW off shore wind farm Anholt, it was possible to perform measurements on a 38.4 km crossbonded cable system. A...

  1. Online fault location on AC cables in underground transmission systems using screen currents

    DEFF Research Database (Denmark)

    Jensen, Christian Flytkjær; Nanayakkara, O.M.K.K; Rajapakse, Athula

    This paper studies online travelling wave methods for fault location on a crossbonded cable system using screen currents. During the construction of the electrical connection to the 400 MW off shore wind farm Anholt, it was possible to perform measurements on a 38.4 km crossbonded cable system. A...

  2. 直接AC/AC变换器输出电压及电流纹波分析%Analysis of Output Voltage and Current Ripple for Direct AC/AC Converter

    Institute of Scientific and Technical Information of China (English)

    文锋; 赵冉; 刘菁

    2009-01-01

    为解决直接AC/AC交换器的输出纹波计算问题,本文建立了以DC/DC变换器结构为基础的六种AC/AC变换器的理想模型.利用这些理想模型,DC/DC变换器的一般分析方法可方便地引入到AC/AC变换器的分析中,然后,论文以Buck型AC/AC变换器为例,给出其电路输出纹波系数的计算公式.为了证明理论分析的正确性,搭建了实验电路,实验结果与理论计算得到了很好的吻合.

  3. Cutaneous metabolism, tissue binding, lipophilicity and electroosmosis : relevance for iontophoretic enhancement

    OpenAIRE

    Altenbach, Melanie Pamela

    2005-01-01

    In this work passive and iontophoretic transport of a dipeptide, Tyrosine-Phenylalanine (TyrPhe), a protected amino acid, Tyrosine-β-Naphthylamide (Tyrβ-NA), and a glucose derivative, Benzyl-2-Acetamido-2-deoxy-α-D-glucopyranoside (BAd-α-Glc), was investigated across heat-separated human epidermis in vitro. The modified Nernst-Planck Equation was used to theoretically describe permeation of these compounds. Permeation experiments were carried out with custom-made glass diffusion cells connect...

  4. Superconducting-magnetic heterostructures: a method of decreasing AC losses and improving critical current density in multifilamentary conductors.

    Science.gov (United States)

    Glowacki, B A; Majoros, M

    2009-06-24

    Magnetic materials can help to improve the performance of practical superconductors on the macroscale/microscale as magnetic diverters and also on the nanoscale as effective pinning centres. It has been established by numerical modelling that magnetic shielding of the filaments reduces AC losses in self-field conditions due to decoupling of the filaments and, at the same time, it increases the critical current of the composite. This effect is especially beneficial for coated conductors, in which the anisotropic properties of the superconductor are amplified by the conductor architecture. However, ferromagnetic coatings are often chemically incompatible with YBa(2)Cu(3)O(7) and (Pb,Bi)(2)Sr(2)Ca(2)Cu(3)O(9) conductors, and buffer layers have to be used. In contrast, in MgB(2) conductors an iron matrix may remain in direct contact with the superconducting core. The application of superconducting-magnetic heterostructures requires consideration of the thermal and electromagnetic stability of the superconducting materials used. On one hand, magnetic materials reduce the critical current gradient across the individual filaments but, on the other hand, they often reduce the thermal conductivity between the superconducting core and the cryogen, which may cause destruction of the conductor in the event of thermal instability. A possible nanoscale method of improving the critical current density of superconducting conductors is the introduction of sub-micron magnetic pinning centres. However, the volumetric density and chemical compatibility of magnetic inclusions has to be controlled to avoid suppression of the superconducting properties.

  5. Effects of ionic strength on passive and iontophoretic transport of cationic permeant across human nail.

    Science.gov (United States)

    Smith, Kelly A; Hao, Jinsong; Li, S Kevin

    2009-06-01

    Transport across the human nail under hydration can be modeled as hindered transport across aqueous pore pathways. As such, nail permselectivity to charged species can be manipulated by changing the ionic strength of the system in transungual delivery to treat nail diseases. The present study investigated the effects of ionic strength upon transungual passive and iontophoretic transport. Transungual passive and anodal iontophoretic transport experiments of tetraethylammonium ion (TEA) were conducted under symmetric conditions in which the donor and receiver had the same ionic strength in vitro. Experiments under asymmetric conditions were performed to mimic the in vivo conditions. Prior to the transport studies, TEA uptake studies were performed to assess the partitioning of TEA into the nail. Permselectivity towards TEA was inversely related to ionic strength in both passive and iontophoretic transport. The permeability and transference number of TEA were higher at lower ionic strengths under the symmetric conditions due to increased partitioning of TEA into the nail. Transference numbers were smaller under the asymmetric conditions compared with their symmetric counterparts. The results demonstrate significant ionic strength effects upon the partitioning and transport of a cationic permeant in transungual transport, which may be instrumental in the development of transungual delivery systems.

  6. Influence of pH on transungual passive and iontophoretic transport.

    Science.gov (United States)

    Smith, Kelly A; Hao, Jinsong; Li, S Kevin

    2010-04-01

    The present study investigated the effects of pH on nail permeability and the transport of ions such as sodium (Na) and chloride (Cl) ions endogenous to nail and hydronium and hydroxide ions present at low and high pH, which might compete with drug transport across hydrated nail plate during iontophoresis. Nail hydration and passive transport of water across the nail at pH 1-13 were assessed. Subsequently, passive and iontophoretic transport experiments were conducted using (22)Na and (36)Cl ions under various pH conditions. Nail hydration was independent of pH under moderate pH conditions and increased significantly under extreme pH conditions (pH >11). Likewise, nail permeability for water was pH independent at pH 1-10 and an order of magnitude higher at pH 13. The results of passive and iontophoretic transport of Na and Cl ions are consistent with the permselective property of nail. Interestingly, extremely acidic conditions (e.g., pH 1) altered nail permselectivity with the effect lasting several days at the higher pH conditions. Hydronium and hydroxide ion competition in iontophoretic transport was generally negligible at pH 3-11 was significant at the extreme pH conditions studied. 2009 Wiley-Liss, Inc. and the American Pharmacists Association

  7. Effective variable switching point predictive current control for ac low-voltage drives

    Science.gov (United States)

    Stolze, Peter; Karamanakos, Petros; Kennel, Ralph; Manias, Stefanos; Endisch, Christian

    2015-07-01

    This paper presents an effective model predictive current control scheme for induction machines driven by a three-level neutral point clamped inverter, called variable switching point predictive current control. Despite the fact that direct, enumeration-based model predictive control (MPC) strategies are very popular in the field of power electronics due to their numerous advantages such as design simplicity and straightforward implementation procedure, they carry two major drawbacks. These are the increased computational effort and the high ripples on the controlled variables, resulting in a limited applicability of such methods. The high ripples occur because in direct MPC algorithms the actuating variable can only be changed at the beginning of a sampling interval. A possible remedy for this would be to change the applied control input within the sampling interval, and thus to apply it for a shorter time than one sample. However, since such a solution would lead to an additional overhead which is crucial especially for multilevel inverters, a heuristic preselection of the optimal control action is adopted to keep the computational complexity at bay. Experimental results are provided to verify the potential advantages of the proposed strategy.

  8. Time-Resolved Magneto-Optical Imaging of Y1Ba2Cu3O7-delta Thin Films in High-Frequency AC Current Regime (Postprint)

    Science.gov (United States)

    2012-02-01

    ΘF=αB laser pulseAC time φ Figure 1. Schematic diagram of the time-resolved MO imaging setup. time-resolved imaging, we use a Q- switched Nd:YLF diode...controlled power source in order to obtain time-resolved MO images of the current flow in the sample. We use a 6 µm thick epitaxial grown ferrite ...the AC current. Ultimately the time resolution achievable with this method will be limited to sub-nanoseconds by the magnetization switching time of the

  9. AC Voltage Control of DC/DC Converters Based on Modular Multilevel Converters in Multi-Terminal High-Voltage Direct Current Transmission Systems

    Directory of Open Access Journals (Sweden)

    Rui Li

    2016-12-01

    Full Text Available The AC voltage control of a DC/DC converter based on the modular multilevel converter (MMC is considered under normal operation and during a local DC fault. By actively setting the AC voltage according to the two DC voltages of the DC/DC converter, the modulation index can be near unity, and the DC voltage is effectively utilized to output higher AC voltage. This significantly decreases submodule (SM capacitance and conduction losses of the DC/DC converter, yielding reduced capital cost, volume, and higher efficiency. Additionally, the AC voltage is limited in the controllable range of both the MMCs in the DC/DC converter; thus, over-modulation and uncontrolled currents are actively avoided. The AC voltage control of the DC/DC converter during local DC faults, i.e., standby operation, is also proposed, where only the MMC connected on the faulty cable is blocked, while the other MMC remains operational with zero AC voltage output. Thus, the capacitor voltages can be regulated at the rated value and the decrease of the SM capacitor voltages after the blocking of the DC/DC converter is avoided. Moreover, the fault can still be isolated as quickly as the conventional approach, where both MMCs are blocked and the DC/DC converter is not exposed to the risk of overcurrent. The proposed AC voltage control strategy is assessed in a three-terminal high-voltage direct current (HVDC system incorporating a DC/DC converter, and the simulation results confirm its feasibility.

  10. Hysteresis losses in MgB{sub 2} superconductors exposed to combinations of low AC and high DC magnetic fields and transport currents

    Energy Technology Data Exchange (ETDEWEB)

    Magnusson, N., E-mail: niklas.magnusson@sintef.no [SINTEF Energy Research, NO-7465 Trondheim (Norway); Abrahamsen, A.B. [DTU Wind Energy, Technical University of Denmark, DK-4000 Roskilde (Denmark); Liu, D. [Electrical Power Processing Group, TU Delft, Mekelweg 4, NL-2628 CD Delft (Netherlands); Runde, M. [SINTEF Energy Research, NO-7465 Trondheim (Norway); Polinder, H. [Electrical Power Processing Group, TU Delft, Mekelweg 4, NL-2628 CD Delft (Netherlands)

    2014-11-15

    Highlights: • A method for calculating hysteresis losses in the low AC – high DC magnetic field and transport current range has been shown. • The method can be used in the design of wind turbine generators for calculating the losses in the generator DC rotor. • First estimates indicate tolerable current ripple in the 0.1% range for a 4 T DC MgB{sub 2} generator rotor coil. - Abstract: MgB{sub 2} superconductors are considered for generator field coils for direct drive wind turbine generators. In such coils, the losses generated by AC magnetic fields may generate excessive local heating and add to the thermal load, which must be removed by the cooling system. These losses must be evaluated in the design of the generator to ensure a sufficient overall efficiency. A major loss component is the hysteresis losses in the superconductor itself. In the high DC – low AC current and magnetic field region experimental results still lack for MgB{sub 2} conductors. In this article we reason towards a simplified theoretical treatment of the hysteresis losses based on available models in the literature with the aim of setting the basis for estimation of the allowable magnetic fields and current ripples in superconducting generator coils intended for large wind turbine direct drive generators. The resulting equations use the DC in-field critical current, the geometry of the superconductor and the magnitude of the AC magnetic field component as parameters. This simplified approach can be valuable in the design of MgB{sub 2} DC coils in the 1–4 T range with low AC magnetic field and current ripples.

  11. Intrawire resistance, AC loss and strain dependence of critical current in MgB2 wires with and without cold high-pressure densification

    NARCIS (Netherlands)

    Zhou, C.; Gao, P.; Krooshoop, H.J.G.; Dhallé, M.M.J.; Sumption, M.D.; Rindfleisch, M.; Tomsic, M.; Küllich, M.; Senatore, C.; Nijhuis, A.

    2014-01-01

    The intrawire resistance and alternating current (AC) loss of two MgB2 wires with filaments surrounded by Nb barriers have been measured and analyzed. Relatively high values of filament-to-matrix contact resistivity are found in the MgB2 wires; the values are two or three orders higher than those co

  12. Critical-current density of melt-grown single-grain Y-Ba-Cu-O disks determined by ac susceptibility measurements

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D-X [ICREA and Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Sanchez, A; Navau, C [Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Shi, Y-H; Cardwell, D A [Engineering Department, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

    2008-08-15

    The field amplitude and frequency dependent complex ac susceptibility {chi}(H{sub m},f) of three Y-Ba-Cu-O disks made by a top-seeded melt growth technique has been measured at 77 K with the ac field applied along the c-axis of the samples (parallel to their thickness). A procedure based on the Bean model has been developed to calculate the critical-current density J{sub c} near the surface of the sample from the measured {chi}(H{sub m}) for the case where the maximum imaginary component {chi}{sup ''} is not reached.

  13. 基于DDS技术的交流恒流源设计%Design of AC constant current source based on DDS

    Institute of Scientific and Technical Information of China (English)

    黄怡然; 李娜

    2011-01-01

    The design and the implement method of AC constant current source with the ML2035 sine signal generator based on DOS was introduced in this paper, the AC constant current source was a closed-loop control system, and current negative feedback loop circuit. The testing results show the output current is between 100-200 mA.%介绍了运用直接数字合成技术( DDS )研制的ML2035正弦信号发生器来实现交流恒流源的设计思想和实现方法.该恒流源是一闭环控制系统、电流负反馈电路,测试结果表明,输出电流在100~ 200 mA范围内.

  14. Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

    Science.gov (United States)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

  15. Influence of pH on Transungual Passive and Iontophoretic Transport

    OpenAIRE

    Smith, Kelly A.; HAO, JINSONG; Li, S. Kevin

    2010-01-01

    The present study investigated the effects of pH on nail permeability and the transport of ions such as sodium (Na) and chloride (Cl) ions endogenous to nail and hydronium and hydroxide ions present at low and high pH, which might compete with drug transport across hydrated nail plate during iontophoresis. Nail hydration and passive transport of water across the nail at pH 1–13 were assessed. Subsequently, passive and iontophoretic transport experiments were conducted using 22Na and 36Cl ions...

  16. Influence of pH on Transungual Passive and Iontophoretic Transport

    OpenAIRE

    Smith, Kelly A; Hao, Jinsong; Li, S. Kevin

    2010-01-01

    The present study investigated the effects of pH on nail permeability and the transport of ions such as sodium (Na) and chloride (Cl) ions endogenous to nail and hydronium and hydroxide ions present at low and high pH, which might compete with drug transport across hydrated nail plate during iontophoresis. Nail hydration and passive transport of water across the nail at pH 1–13 were assessed. Subsequently, passive and iontophoretic transport experiments were conducted using 22Na and 36Cl ions...

  17. Role of transdermal potential difference during iontophoretic drug delivery.

    Science.gov (United States)

    Bandrivskyy, Andriy; Bernjak, Alan; McClintock, Peter V E; Stefanovska, Aneta

    2004-09-01

    Potential differences have been measured during transdermal iontophoresis in order to establish the effect of voltage, as opposed to current, on cutaneous blood flow. It is known that, even in the absence of drugs, the iontophoresis current can sometimes produce increased blood flow. The role of voltage in this process is studied through single-ended measurements (between electrode and body) of the potential difference during iontophoresis with 100-microA, 20-s current pulses through deionized water, saturated 20.4% NaCl solution, 1% acetylcholine, and 1% sodium nitroprusside. It is found that the voltage needed to deliver the current varied by orders of magnitudes less than the differences in the conductance of these different electrolytes, and it is concluded that, at least for the present current protocol, the voltage as such is not an important factor in increasing the blood flow.

  18. Beta band transcranial alternating (tACS and direct current stimulation (tDCS applied after initial learning facilitate retrieval of a motor sequence

    Directory of Open Access Journals (Sweden)

    Vanessa eKrause

    2016-01-01

    Full Text Available The primary motor cortex (M1 contributes to the acquisition and early consolidation of a motor sequence. Although the relevance of M1 excitability for motor learning has been supported, the significance of M1 oscillations remains an open issue. This study aims at investigating to what extent retrieval of a newly learned motor sequence can be differentially affected by motor-cortical transcranial alternating (tACS and direct current stimulation (tDCS. Alpha (10 Hz, beta (20 Hz or sham tACS was applied in 36 right-handers. Anodal or cathodal tDCS was applied in 30 right-handers. Participants learned an eight-digit serial reaction time task (SRTT; sequential vs. random with the right hand. Stimulation was applied to the left M1 after SRTT acquisition at rest for ten minutes. Reaction times were analyzed at baseline, end of acquisition, retrieval immediately after stimulation and reacquisition after eight further sequence repetitions.Reaction times during retrieval were significantly faster following 20 Hz tACS as compared to 10 Hz and sham tACS indicating a facilitation of early consolidation. TDCS yielded faster reaction times, too, independent of polarity. No significant differences between 20 Hz tACS and tDCS effects on retrieval were found suggesting that 20 Hz effects might be associated with altered motor-cortical excitability. Based on the behavioural modulation yielded by tACS and tDCS one might speculate that altered motor-cortical beta oscillations support early motor consolidation possibly associated with neuroplastic reorganization.

  19. Liquid helium boil-off measurements of heat leakage from sinter-forged BSCCO current leads under DC and AC conditions

    Science.gov (United States)

    Cha, Y. S.; Niemann, R. C.; Hull, J. R.; Youngdahl, C. A.; Lanagan, M. T.; Nakade, M.; Hara, T.

    1995-06-01

    Liquid helium boil-off experiments are conducted to determine the heat leakage rate of a pair of BSCCO 2223 high-temperature superconductor current leads made by sinter forging. The experiments are carried out in both DC and AC conditions and with and without an intermediate heat intercept. Current ranges are from 0-500 A for DC tests and 0-1,000 A(sub rms) for AC tests. The leads are self-cooled. Results show that magnetic hysteresis (AC) losses for both the BSCCO leads and the low-temperature superconductor current jumper are small for the current range. It is shown that significant reduction in heat leakage rate (liquid helium boil-off rate) is realized by using the BSCCO superconductor leads. At 100 A, the heat leakage rate of the BSCCO/copper binary lead is approximately 29% of that of the conventional copper lead. Further reduction in liquid helium boil-off rate can be achieved by using an intermediate heat intercept. For example, at 500 K, the heat leakage rate of the BSCCO/copper binary lead is only 7% of that of the conventional copper lead when an intermediate heat intercept is used.

  20. Patient considerations in the use of transdermal iontophoretic fentanyl for acute postoperative pain

    Directory of Open Access Journals (Sweden)

    Hartrick CT

    2016-04-01

    Full Text Available Craig T Hartrick,1 Cecile R Pestano,1 Li Ding,2 Hassan Danesi,2 James B Jones,2 1Beaumont Health System, Troy, MI, 2The Medicines Company, Parsippany, NJ, USA Abstract: Opioids are commonly used in the management of moderate-to-severe postoperative pain. Patient-controlled analgesic techniques are recognized as preferred administration methods. Previously, research has focused on intravenously administered opioids via a programmable pump. More recently, an iontophoretic transdermal system (ITS, which is patient controlled, has been developed. The focus of this review is on pain management using the fentanyl ITS during the 24–72-hour time period immediately following surgery. Fentanyl ITS offers a needle-free alternative to traditional intravenous (IV patient-controlled analgesia (PCA system that is as effective and safe as IV PCA. This system is easy to use for both patients and nurses. The use of fentanyl ITS is generally associated with a better ease-of-care profile, including a greater ease of mobility, from a patients' perspective when compared with morphine IV PCA. Keywords: patient-controlled analgesia, fentanyl iontophoretic transdermal system, ease of care, mobility, patient perspective, review

  1. Iontophoretic delivery of lipophilic and hydrophilic drugs from lipid nanoparticles across human skin.

    Science.gov (United States)

    Charoenputtakun, Ponwanit; Li, S Kevin; Ngawhirunpat, Tanansait

    2015-11-10

    The combined effects of iontophoresis and lipid nanoparticles on drug delivery across human epidermal membrane (HEM) were investigated. The delivery of lipophilic and hydrophilic drugs, all trans-retinoic acid (ATRA), salicylate (SA), and acyclovir (ACV), across HEM from lipid nanoparticles, solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), was compared in passive and iontophoresis experiments in vitro. Iontophoresis experiments were also performed with synthetic Nuclepore membrane for comparison. Drug distribution in the skin after iontophoretic delivery with the lipid nanoparticles was examined using a model probe rhodamine B base (RhoB). The drug-loaded lipid nanoparticles had average sizes of ∼ 118-169 nm and a negative zeta potential. Iontophoresis did not enhance the delivery of ATRA across HEM from SLN and NLC. However, HEM distribution study of RhoB suggested that lipophilic drugs could be delivered into the deeper layer of the skin following iontophoretic delivery of the drugs from the lipid nanoparticles. Iontophoresis enhanced the delivery of hydrophilic drug SA with the lipid nanoparticles. Similarly, iontophoresis enhanced the delivery of ACV when it was loaded in SLN. These results suggest that lipid nanoparticles are a promising drug delivery method that can be combined with iontophoresis to improve skin delivery of hydrophilic drugs.

  2. The response of single melanophores to extracellular and intracellular iontophoretic injection of melanocyte-stimulating hormone.

    Science.gov (United States)

    Horowitz, J M; Mikuckis, G M; Longshore, M A

    1980-03-01

    The purpose of this study was to determine if MSH, a peptide hormone, injected within a frog skin melanophore could elicit a physiological response, melanosome dispersion. Multibarreled electrodes were used to iontophoretically inject alpha-MSH inside frog skin melanophores of Rana pipiens pipiens. In 46 cells, intracellular MSH was ineffective in producing melanosome dispersion as viewed through the microscope. Because the frog skin is a complex of closely spaced cells, at times the microelectrode may have impaled cells other than melanophores. Therefore, in order to verify that the electrode was in a melanophore and not some other cell type, cAMP, shown to produce melanosome dispersion, was iontophoretically injected to 17 cells, causing the melanosomes to disperse. In these 17 cells, prior injection of MSH caused no dispersion. The response was monitored by observing the target cell with surrounding cells serving as a control. As an additional control to determine if adequate amounts of MSH were released, the electrode was withdrawn from the cell and placed near a group of melanophores, and in all cases the cells close to the electrode tip showed melanosome dispersion after MSH injection. The results of this study remain consistent with the view that MSH receptors in frog skin melanophores are located on the external surface of the plasma membrane, and MSH injected into the cytoplasm of the cell has no short term effect.

  3. The in vitro and in vivo evaluation of new synthesized prodrugs of 5-OH-DPAT for iontophoretic delivery

    NARCIS (Netherlands)

    Ackaert, O. W.; De Graan, J.; Capancioni, R.; Della Pasqua, O. E.; Dijkstra, D.; Westerink, B. H.; Danhof, M.; Bouwstra, J. A.

    2010-01-01

    The feasibility of transdermal iontophoretic transport of 4 novel ester prodrugs of 5-OH-DPAT (glycine-, proline-, valine- and (beta-alanine-5-OH-DPAT) was investigated in vitro and in vivo. Based on the chemical stability of the prodrugs, the best candidates were selected for in vitro transport stu

  4. NEUROCHEMICAL LESIONING IN THE RAT-BRAIN WITH IONTOPHORETIC INJECTION OF THE 1-METHYL-4-PHENYLPYRIDINIUM ION (MPP+)

    NARCIS (Netherlands)

    TERHORST, GJ; KNIGGE, MF; VANDERWAL, A

    1992-01-01

    Iontophoretic injections of the 1-methyl-4-phenylpyridinium ion (MPP+) were made in the dopaminergic part of the substantia nigra to see whether this injection technique could be used for inducing localized neurochemical lesions in dopaminergic cell groups and to assess the effects of MPP+ on non-do

  5. Modulated iontophoretic delivery of small and large molecules through microchannels.

    Science.gov (United States)

    Kumar, Vijay; Banga, Ajay K

    2012-09-15

    The objective of this work was to modulate transdermal drug delivery by iontophoresis though skin microchannels created by microneedles. Calcein and human growth hormone were used as a model small and large molecule, respectively. In vitro permeation studies were performed on porcine ear skin under three different settings: (a) modulated iontophoresis alone, (b) pretreatment with microneedles and (c) combination of microneedles pretreatment and modulated iontophoresis. For modulated iontophoresis, 0.5 mA/cm(2) current was applied for 1h each at 2nd and 6th hour of the study. Methylene blue staining, calcein imaging and pore permeability index suggested maltose microneedles created uniform microchannels in skin. Application of iontophoresis provided two peaks in flux of 1.04 μg/(cm(2)h) at 4th hour and 2.09 μg/(cm(2)h) at 8th hour of study for calcein. These peaks in flux were significant higher when skin was pretreated with microneedles (piontophoresis. This combination also provided significant increase in cumulative amount of calcein and human growth hormone delivered as compared to microneedles or iontophoresis alone (piontophoresis can be used to modulate drug delivery across skin microchannels created by microneedles.

  6. Large A.C. machines theory and investigation methods of currents and losses in stator and rotor meshes including operation with nonlinear loads

    CERN Document Server

    Boguslawsky, Iliya; Hayakawa, Masashi

    2017-01-01

    In this monograph the authors solve the modern scientific problems connected with A.C. motors and generators, based first on the detailed consideration of their physical phenomena. The authors describe the theory and investigative methods they developed and applied in practice, which are considered to be of essential interest for specialists in the field of the electrical engineering industry in European countries, the USA, Argentina, and Brazil, as well as in such countries as India, China, and Iran. This book will be of interest to engineers specialized in the field of the manufacture, operation, and repair of A.C. machines (motors and generators) as well as electric drives; to professors, lecturers, and post-graduate students of technical universities, who are specializing in the field of electric machine engineering and electric drives; and to students who are engaged in the field of high current techniques, electric drives, and electric machine engineering.

  7. Technology of Zero-Current Breaking of Intelligent AC Contactor%智能交流接触器零电流分断技术

    Institute of Scientific and Technical Information of China (English)

    鲍光海; 张培铭

    2012-01-01

    Zero-current breaking technology is an important content in the research of intelligent AC contactor, In this paper, the optimization calculation aimed to breaking quickly of the electromagnetic mechanism of the intelligent AC contactor is conducted, by using the ANSYS electromagnetic software and the artificial fish swarm optimization algorithm based on genetic algorithm. This method not only ensures the reliable contact process of the intelligent AC contactor, but also realizes a quick release of the executive mechanism, thus greatly reduces the influence to the stability and accuracy of the three-phase contactors, especially the first opening phase when zero-current breaking, which improves the reliability of zero-current breaking and increases the technology research level of the intelligent AC contactor. A prototype is made based on the results of the optimization designation. The testing results show that the breaking time of the intelligent AC contactor is shortened greatly, and the stability of the breaking time is improved significantly too, so the reliability of the zero-current breaking increases significantly.%零电流分断技术是交流接触器智能化研究的重要内容。本文采用Ansys电磁场软件和基于遗传算法的人工鱼群优化算法对智能交流接触器电磁动作机构进行以快速分断为目标的优化计算,不仅保证智能交流接触器可靠与优化的接通过程,而且实现了动作机构快速释放,从而大幅度减小机构分散性对三相触头特别是首开相触头零电流分断准确性与稳定性影响,提高零电流分断的可靠性,从而提高了交流接触器智能化技术的研究水平。根据优化设计结果加工了样机,对样机测试与试验的结果表明,智能交流接触器的分断时间大幅缩短,三相触头分断时间稳定性也得到明显改善,因此零电流分断的可靠性显著提高。

  8. In vivo determination of the diclofenac skin reservoir: comparison between passive, occlusive, and iontophoretic application.

    Science.gov (United States)

    Clijsen, Ron; Baeyens, Jean Pierre; Barel, André Odilon; Clarys, Peter

    2015-01-01

    There is scarce information concerning the pharmacodynamic behavior of topical substances used in the physiotherapy setting. The aim of the present study was to estimate the formation and emptying of the diclofenac (DF) skin reservoir after passive, semiocclusive, and electrically assisted applications of DF. Five different groups of healthy volunteers (ntotal=60, 23 male and 37 female), participated in this study. A 1% DF (Voltaren Emulgel) formulation (12 mg) was applied on the volar forearms on randomized defined circular skin areas of 7 cm(2). DF was applied for 20 minutes under three different conditions at the same time. The presence of DF in the skin results in a reduction of the methyl nicotinate (MN) response. To estimate the bioavailability of DF in the skin, MN responses at different times following initial DF application (1.5, 6, 24, 32, 48, 72, 96, and 120 hours) were analyzed. At 1.5 hours after the initial DF application, a significant decrease in MN response was detected for the occluded and iontophoretic delivery. Passive application resulted in a decrease of the MN response from 6 hours post-DF application. The inhibition remained up to 32 hours post-DF application for the iontophoretic delivery, 48 hours for the occluded application, and 72 hours for the passive delivery. At 96 and 120 hours post-DF application none of the MN responses was inhibited. The formation and emptying of a DF skin reservoir was found to be dependent on the DF-application mode. Penetration-enhanced delivery resulted in a faster emptying of the reservoir.

  9. In vivo determination of the diclofenac skin reservoir: comparison between passive, occlusive, and iontophoretic application

    Directory of Open Access Journals (Sweden)

    Clijsen R

    2015-02-01

    Full Text Available Ron Clijsen,1,2 Jean Pierre Baeyens,2 André Odilon Barel,2 Peter Clarys2 1Department of Health Sciences, University of Applied Sciences and Arts of Southern Switzerland, Landquart, Switzerland; 2Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium Aim: There is scarce information concerning the pharmacodynamic behavior of topical substances used in the physiotherapy setting. The aim of the present study was to estimate the formation and emptying of the diclofenac (DF skin reservoir after passive, semiocclusive, and electrically assisted applications of DF.Subjects and methods: Five different groups of healthy volunteers (ntotal=60, 23 male and 37 female, participated in this study. A 1% DF (Voltaren Emulgel formulation (12 mg was applied on the volar forearms on randomized defined circular skin areas of 7 cm2. DF was applied for 20 minutes under three different conditions at the same time. The presence of DF in the skin results in a reduction of the methyl nicotinate (MN response. To estimate the bioavailability of DF in the skin, MN responses at different times following initial DF application (1.5, 6, 24, 32, 48, 72, 96, and 120 hours were analyzed.Results: At 1.5 hours after the initial DF application, a significant decrease in MN response was detected for the occluded and iontophoretic delivery. Passive application resulted in a decrease of the MN response from 6 hours post-DF application. The inhibition remained up to 32 hours post-DF application for the iontophoretic delivery, 48 hours for the occluded application, and 72 hours for the passive delivery. At 96 and 120 hours post-DF application none of the MN responses was inhibited.Conclusion: The formation and emptying of a DF skin reservoir was found to be dependent on the DF-application mode. Penetration-enhanced delivery resulted in a faster emptying of the reservoir. Keywords: transdermal drug delivery, passive diffusion, occlusion

  10. An Improvement on Current Sharing Characteristics of Poloidal Field (PF)-AC-DC Converters%An Improvement on Current Sharing Characteristics of Poloidal Field (PF)-AC-DC Converters

    Institute of Scientific and Technical Information of China (English)

    陈鹏; 傅鹏; 宋执权

    2011-01-01

    In response to the current imbalance phenomenon and its harmfulness, a current sharing circuit model is built up, which reveals the underlying causes for the current imbalance through a quantitative analysis. Then, a feasible approach of improvement, namely enlargement of the length of connection busbars, is proposed. After the amendment, it can be seen that the current sharing coefficient is ahnost unity under rated or fault current conditions.

  11. Influence of metallic trays on the ac resistance and ampacity of low-voltage cables under non-sinusoidal currents

    Energy Technology Data Exchange (ETDEWEB)

    Demoulias, Charis; Labridis, Dimitris P.; Dokopoulos, Petros; Gouramanis, Kostas [Aristotle University of Thessaloniki, Department of Electrical and Computer Engineering, Thessaloniki (Greece)

    2008-05-15

    This paper investigates the influence of metallic trays on the ac resistance of PVC insulated, low-voltage (0.6/1.0 kV) cables made according to CENELEC standard HD603. The investigation is made with a validated finite element model for the fundamental and higher harmonic frequencies. It is shown that the cable's effective resistance is affected significantly by the relative magnetic permeability and specific conductivity of the tray, while the tray's dimensions do not affect it. The orientation of the cable with respect to the tray also influences the ac resistance of the phase and neutral conductors. An ampacity derating factor is defined and calculated for various cable cross-sections and harmonic loads. The presence of a metallic tray is shown to cause an additional derating of cable's ampacity which is relatively significant at large cable cross-sections. Working examples demonstrate the application of the results in calculating the ampacity of low-voltage cables and in assessing the energy savings that will result from the use of active harmonic filters. (author)

  12. A Circulating-Current Suppression Method for Parallel Connected Voltage Source Inverters (VSI) with Common DC and AC Buses

    DEFF Research Database (Denmark)

    Wei, Baoze; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2017-01-01

    applications. The basic concept of the proposed circulating-current suppression method is to modify the original current references by using the current difference among the parallel inverters. In the proposed approach, both of cross circulating-current and zero-sequence circulating-current are considered...... on the virtual impedance. Further, a circulating-current control loop is added to improve the average current-sharing performance among parallel VSIs. Experimental results are presented to show the effectiveness of the proposed control method to suppress both of the cross and zero-sequence circulating-currents....

  13. Measurement of AC transport current losses in YBCO coated conductor%高温超导YBCO带材的交流传输电流损耗测量

    Institute of Scientific and Technical Information of China (English)

    李晓群; 何清; 金涛; 周世平; 李敬东; 任丽; 唐跃进

    2012-01-01

    In this paper, the AC transport current losses of YBCO coated conductor was studied under different currents and different frequencies respectively. The YBCO tape used in this experiment was SCS4050 produced by Superpower Inc. , which was measured in liquid nitrogen (77 K) by a sensitive electrical method with a lock -in amplifier. The measured AC transport current losses results were compared with the Norris formula calculative results when the power frequency equaled to 50 Hz. The measured results in different frequencies which varied from 15Hz to 300Hz were also provided.%文中对不同频率不同幅值的交变电流下高温超导体YBCO带材的交流传输损耗进行了实验研究.实验在77K下,对Superpower公司生产的SCS4050型号带材采用电测法通过锁相放大器进行了交流损耗值的测量,并将其工作电流为50Hz时的测量结果与Norris矩形模型估算值进行了对比,同时也给出了15Hz到300Hz不同频率下交流损耗测量结果的比较分析.

  14. A Circulating Current Suppression Method for Parallel Connected Voltage-Source-Inverters (VSI) with Common DC and AC Buses

    DEFF Research Database (Denmark)

    Wei, Baoze; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2016-01-01

    on circulating current control loops used to modify the reference currents by compensating the error currents among parallel inverters. Both of the cross and zero-sequence circulating currents are considered. The proposed method is coordinated together with droop and virtual impedance control. In this paper...... loop is added to acquire a better average current sharing performance among parallel VSIs, which can effectively suppress both of the cross and zero-sequence circulating currents. Experimental results are presented in order to verify the effectiveness of the proposed control strategy....

  15. Evaluation of levels of defect sites present in highly ordered pyrolytic graphite electrodes using capacitive and faradaic current components derived simultaneously from large-amplitude Fourier transformed ac voltammetric experiments.

    Science.gov (United States)

    Lee, Chong-Yong; Bond, Alan M

    2009-01-15

    The level of edge plane defect sites present in highly ordered pyrolytic graphite (HOPG) electrodes has been evaluated via analysis of dc, ac fundamental, and higher-order ac harmonics available from a single large-amplitude Fourier transformed (FT) ac voltammetric experiment. Deliberate introduction of a low level of edge plane defect was achieved by polishing, with a higher level being introduced via electrochemical pretreatment. Kinetics regimes associated with fast electron transfer on the edge plane defect sites and slow electron transfer on the basal plane surface are resolved under ac conditions when using the surface-sensitive [Fe(CN)(6)](3-/4-) redox probe. However, because of their insensitivity to slow electron transfer, higher-order ac faradaic harmonics almost exclusively detect only the much faster processes that emanate from edge plane defect sites. Thus, detection of fourth- and higher-order ac Faradaic harmonic components that are devoid of background capacitive current is possible at freshly cleaved HOPG in the region near the reversible potential for the [Fe(CN)(6)](3-/4-) process. Under these circumstances, dc cyclic voltammograms exhibit only reduction and oxidation peaks separated by more than 1 V. The fundamental ac harmonic provides detailed information on the capacitive current, which increases with the level of edge plane defect sites. Apparent charge transfer rate constants also can be derived from peak-to-peak separations obtained from the dc aperiodic component. Estimates of the percentage of edge plane defect sites based on ac higher harmonics, capacitance, and dc aperiodic component that are available from a single experiment have been compared. The edge plane defect levels deduced from capacitance (fundamental harmonic ac component) and higher harmonic Faradaic currents are considered to be more reliable than estimations based on apparent rate constants derived from the dc aperiodic component or conventional dc cyclic voltammogram.

  16. Currents, magnetization and AC-losses of YBa 2Cu 3O 7 superconductors in rapidly changing magnetic fields

    Science.gov (United States)

    Kwasnitza, K.; Plotzner, V.; Waldmann, M.; Widmer, E.

    1988-06-01

    In YBa 2Cu 3O 7 samples of different shape time dependent magnetization currents were induced at 4.2K by the application of rapid magnetic field changes. This contactless method allows the study of the intergrain and intragrain currents in the resistive flux flow state.

  17. HVDC交流滤波器合闸的涌流研究%Simulation of Inrush Current at HVDC AC Filter Switching on

    Institute of Scientific and Technical Information of China (English)

    丛宝丰; 夏成军; 席亮

    2013-01-01

    HVDC系统交流滤波器的投入会产生较大涌流,会造成滤波器损坏,保护误动作,威胁系统安全.针对上述问题,采用了基于蒙特卡洛算法与自定义建模的仿真研究,对逆变侧滤波器涌流与表征三相电流不平衡性的零序电流进行了详细的计算,基于计算结果,提出加装POW装置与临时闭锁不平衡保护等抑制涌流影响的方法.%In HVDC system,the AC filter will produce larger inrush current during switching, which will cause damage to the filters, protection misoperation and threat to DC system security. To solve the problem, a simulation based on Monte Carlo algorithm and PSCAD user-definition model has been come up with. Make a lot of simulations about inrush current and the zero sequence current which stands for three-phase unbalanced inrush current at the inverter side. Based on these results, some methods which solve the effect of inrush current has been come up with, like erecting POW, locking the unbalanced protection temporarily.

  18. Pulse pattern modulated strategy for harmonic current components reduction in three-phase AC-DC converters

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2015-01-01

    Generated harmonic current as a consequence of employing power electronics converter is known as an important power quality issue in distribution networks. From industry point of view complying with international standards is mandatory, however cost and efficiency are two other important features......, which need to be considered in order to be competitive in the market. Therefore, having a flexibility to meet various requirements imposed by the standard recommendations or costumer needs is at most desirable. This makes the generated harmonic current mitigation a challenging task especially with three......-phase diode bridge rectifier, which still is preferred in many power electronic systems. This paper addresses a novel current modulation strategy using a single-switch boost three-phase diode bridge rectifier. The proposed method can selectively mitigate current harmonics, which makes it suitable...

  19. Iontophoretic Delivery of Riboflavin into the Rabbit Cornea:a Primary Study

    Institute of Scientific and Technical Information of China (English)

    Na Li; Xiujun Peng; Zhengjun Fan; Yu Xia

    2014-01-01

    Purpose:.To determine the penetrability of riboflavin into the corneal stroma by iontophoresis and to compare the perme-ability effects of different solvents. Methods:.Twenty rabbits were randomly divided into four groups:.a group that received 0.1% riboflavin-balanced salt solution (BSS) by iontophoresis, a group that received 0.1%riboflavin-saline solution by iontophoresis,.a group that re-ceived 0.1% riboflavin-distilled water solution by iontophore-sis, and a control group that received classical riboflavin in-stillation after corneal de-epithelialization..The degree of yel-lowing of the de-epithelialized corneal stromal button from each rabbit was compared. Results:.The yellow color scores for the corneal stromal but-tons in the three iontophoresis groups were compared with those of control group..Iontophoretic delivery of a 0.1% ri-boflavin-distilled water solution yielded similar yellow changes in the corneal stromal button when compared with classical ri-boflavin instillation after de-epithelialization..However,.the other two solvents did not sufficiently enhance the permeabili-ty of riboflavin. Conclusion:.Riboflavin can effectively penetrate into the corneal stroma to saturation levels by iontophoresis..Using distilled water as the solvent can promote penetrability.. (Eye Science 2014; 29:30-35).

  20. NO Exchange for a Water Molecule Favorably Changes Iontophoretic Release of Ruthenium Complexes to the Skin

    Directory of Open Access Journals (Sweden)

    Danielle C. A. S. de Santana

    2017-01-01

    Full Text Available Ruthenium (Ru complexes have been studied as promising anticancer agents. Ru nitrosyl complex (Ru-NO is one which acts as a pro-drug for the release of nitric oxide (NO. The Ru-aqueous complex formed by the exchange of NO for a water molecule after NO release could also possess therapeutic effects. This study evaluates the influence of iontophoresis on enhancing the skin penetration of Ru-NO and Ru-aqueous and assesses its applicability as a tool in treating diverse skin diseases. Passive and iontophoretic (0.5 mA·cm−2 skin permeation of the complexes were performed for 4 h. The amount of Ru and NO in the stratum corneum (SC, viable epidermis (VE, and receptor solution was quantified while the influence of iontophoresis and irradiation on NO release from Ru-NO complex was also evaluated. Iontophoresis increased the amount of Ru-NO and Ru-aqueous recovered from the receptor solution by 15 and 400 times, respectively, as compared to passive permeation. Iontophoresis produced a higher accumulation of Ru-aqueous in the skin layers as compared to Ru-NO. At least 50% of Ru-NO penetrated the SC was stable after 4 h. The presence of Ru-NO in this skin layer suggests that further controlled release of NO can be achieved by photo-stimulation after iontophoresis.

  1. Dynamic modelling and robust current control of wind-turbine driven DFIG during external AC voltage dip

    Institute of Scientific and Technical Information of China (English)

    HU Jia-bing; HE Yi-kang

    2006-01-01

    Doubly-FedInduction Generator (DFIG), with vector control applied, is widely used in Variable-Speed ConstantFrequency (VSCF) windenergy generation system and shows good performance in maximum wind energy capture. But in two traditional vector control schemes, the equivalent stator magnetizing current is considered invariant in order to simplify the rotor current inner-loop controller. The two schemes can perform very well when the grid is in normal condition. However, when grid disturbance such as grid voltage dip or swell fault occurs, the control performance worsens, the rotor over current occurs and the Fault Ride-Through (FRT) capability of the DFIG wind energy generation system gets seriously deteriorated. An accurate DFIG model was used to deeply investigate the deficiency of the traditional vector control. The improved control schemes of two typical traditional vector control schemes used in DFIG were proposed, and simulation study of the proposed and traditional control schemes, with robust rotor current control using Internal Model Control (IMC) method, was carried out. The validity of the proposed modified schemes to control the rotor current and to improve the FRT capability of the DFIG wind energy generation system was proved by the comparison study.

  2. Time-resolved magneto-optical imaging of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films in high-frequency AC current regime

    Energy Technology Data Exchange (ETDEWEB)

    Lucarelli, A [Department of Applied Science, College of William and Mary, Williamsburg, VA 23187-8795 (United States); Luepke, G [Department of Applied Science, College of William and Mary, Williamsburg, VA 23187-8795 (United States); Haugan, T J [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433-7919 (United States); Levin, G A [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433-7919 (United States); Barnes, P N [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433-7919 (United States)

    2006-06-15

    We present a time-resolved magneto-optical (MO) imaging study of high-temperature superconductor (HTS) in a high-frequency alternating current (AC) regime. The evolution of the magnetic flux density distribution in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) thin film samples is studied as a function of the phase of the applied AC current. A quantitative analysis of the data shows that the maxima of the AC current density is shifted from the edges further inside the sample, which may be caused by the higher self-induced field in that region. This technique can be used to study magnetic flux evolution in HTS films and coated conductors in the high-frequency current regime.

  3. Software Development for DC Current Distribution in AC Power Grid%交流电网直流电流分布仿真软件的开发

    Institute of Scientific and Technical Information of China (English)

    汪发明; 张露; 全江涛; 谢齐家; 潘卓洪; 文习山

    2012-01-01

    为量化分析高压直流输电入地电流(简称直流电流)在交流电网内的分布,提出了直流分布的完整理论分析模型,实现了变电站地下网络的Thevenin等效;借助潮流计算数据取得交流电网的接线信息,开发了潮流计算接口,解决了现代大型交流电网接线运行方式的数据输入问题。运用随机模拟试验方法探讨交流电网直流分布的机理,分析了交流电网内的直流电流的分布规律:交流电网规模越大直流电流分布越广;杆塔-避雷线系统的存在会使交流电网直流电流分布密集;采用抑制措施后交流电网局部直流电流分布可能更加密集,但直流电流分布总量下降。仿真软件适用于大型交流电网直流电流分布的预测计算和抑制措施的仿真评估,可以为更好地分析、预报和抑制直流电流分布及其不良影响提供参考。%In order to analyze the HVDC transmission's earth-return current distribution in AC power grids,an improved theoretical model is set up realizing the Thevenin equivalence of underground networks.A power flow calculation interface is developed to load data of the connection of modern large-scale AC grid.Then the random test method was used to summarize the rules of DC current distribution.The results are gained as follows:the larger the AC grid,the more the DC current distribution is caused;the DC current distribution is increased by towers and overhead ground wires;though the local DC current distribution is increased,the total DC current distribution is suppressed by mitigation methods.The simulation software is suitable for DC current distribution computation and evaluating the mitigation methods,and it provides reference for analysis,forecast,mitigation,and adverse effects of DC current distributions.

  4. Effective Leadership and Management of an ACS Injury Prevention Program: Current Opinions and Perspectives From Where the Rubber Meets the Road.

    Science.gov (United States)

    Wolfe, Elizabeth S; Bryant, Elizabeth A

    The American College of Surgeons (ACS) mandates that each verified trauma center must have an injury prevention coordinator (IPC); however, Chapter 18 in the Resources for Optimal Care of the Injured Patient (2014) provides minimal information on how to effectively lead or manage an injury prevention (IP) program. This opinion article addresses 3 fundamental components of an effective IP program: (1) construction of an innovative vision of IP programming using current technology; (2) intentional investment and involvement; and (3) stakeholder leadership, engagement, and sustainability. This article also provides leadership and management methods from other professions both within and outside of the health care field that can be translated into sustainable IP program planning, implementation, and longevity.

  5. Critical current densities of Sr0.6K0.4Fe2As2 superconductors estimated from AC susceptibilities

    Science.gov (United States)

    Setoyama, Subaru; Kinoshita, Junichi; Akune, Tadahiro; Sakamoto, Nobuyoshi; Murakami, Kouji; Yoshida, Nobuyuki; Kiuchi, Masaru; Otabe, Edmund Soji; Matsushita, Teruo; Ge, Jun; Ni, Baorong; Wang, Lei; Qi, Yanpeng; Zhang, Xianping; Gao, Zhaoshun; Ma, Yanwei

    2013-01-01

    AC susceptibilities (real χ‧ and imaginary χ″) of Sr0.6K0.4Fe2As2 (122 type) polycrystalline with Ag addition are analysed by the grained Bean model. A variety of characteristics, double peak in χ″ and shoulder transition in χ‧, appear in the model simulation. Comparing the measured χ‧ and χ″ with the model allows more clear insight on the polycrystalline structure. Estimated critical current densities Jcg and Jcℓ of the grain and the link in the iron-based pnictides show that the addition of 20 wt.% Ag increases Jcℓ 9 times larger. Improvement of intergrain characteristics with Ag addition is clearly indicated.

  6. Fentanyl iontophoretic transdermal system in postoperative pain management%芬太尼离子渗透经皮给药系统在术后疼痛治疗中的应用

    Institute of Scientific and Technical Information of China (English)

    喻洁; 黄宇光

    2011-01-01

    背景 盐酸芬太尼离子渗透经皮给药系统(fentanyl Hcl iontophoretic transdermal system,fentanyl,ITS)是通过电离子渗透技术经体表的微弱电场由皮肤给予芬太尼,产生镇痛作用的给药装置.已在美国和欧洲批准上市,用于治疗中到重度的手术后疼痛.目的 主要回顾了在欧美针对该给药系统所进行的一系列临床试验.内容 安慰剂对照试验和阳性药物平行对照试验均证实,以离子渗透技术经皮给予芬太尼对多种手术后疼痛有良好的治疗作用.该给药系统具有与标准的吗啡患者自控镇痛(patient-controlled analgesia,PCA)相似的有效性和安全性.趋向 ITS具有无创,有效,安全,简单,易于为患者接受等优点,为临床提供了一种全新的PCA方式.%Background The fentanyl hydrochloride iontophoretic transdermal system(fentanyl ITS)is a needle-free,selfcontained drug-delivery system that uses iontophoretic technology to deliver fentanyl through the skin by application of a low-intensity electrical field.It has been approved in the USA and Europe for the management of acute,moderate-to-severe postoperative pain.Objective This review focus on several clinical trails of fentanyl ITS,which have been carried out in America and Europe.Content In three phase 3 placebo-controlled trials,fentanyl ITS was shown to be superior to placebo for the treatment of postoperative pain following major abdominal,orthopedic and thoracic surgery.The results of several active-comparator phase 3 trial demonstrated comparable safety and efficacy with a standard morphine intravenous patient-controlled analgesia(Ⅳ-PCA)dosing regimen,without significant difference in the side effect profile.Trend Fentanyl ITS is a novel patient-controlled analgesia(PCA)system allowing patients to self-administer pre-programmed doses of fentanyl.It represents a safe,easy to use,non-invasive and convenient alternative to current acute postoperative pain management modalities.

  7. Sumatriptan transdermal iontophoretic patch (NP101-Zelrix™: review of pharmacology, clinical efficacy, and safety in the acute treatment of migraine

    Directory of Open Access Journals (Sweden)

    Vikelis M

    2012-09-01

    Full Text Available Michail Vikelis,1 Dimos D Mitsikostas,2 Alan M Rapoport31Glyfada Headache Center, Glyfada, Greece; 2Neurology Department, Athens Naval Hospital, Athens, Greece; 3The David Geffen School of Medicine at UCLA, Los Angeles, CA, USAAbstract: Migraine is a chronic, painful, and often disabling primary headache disorder, typically presenting with recurrent attacks that may be accompanied by a variety of neurological, gastrointestinal, and autonomic symptoms. Gastrointestinal symptoms in association with migraine including, nausea, vomiting, and gastroparesis, affect a large proportion of migraine sufferers. These symptoms may result in delays or inconsistencies in the absorption of oral treatments. Hence, the necessity for an innovative, non-invasive, parenteral delivery formulation for quick and effective treatment of migraine attacks is evident. Iontophoresis utilizes minimal amounts of electrical potential to support the fast transfer of ionized medication transdermally and into the general circulation. Two pharmacokinetic clinical trials have shown that iontophoretic delivery of sumatriptan through the skin produces quick and reproducible therapeutic plasma concentrations. A randomized, double-blind, multicenter, phase III study demonstrated superior efficacy versus placebo and excellent tolerability, with no triptan-related adverse events. The proportion of patients that were pain-free at 2 h post-treatment was 18% for the sumatriptan patch vs 9% for placebo (P = 0.0092; number needed to treat = 11.1. Upon approval from the Food and Drug Administration and other regulatory authorities, the iontophoretic transdermal delivery of sumatriptan will be a good choice for patients experiencing poor absorption of oral medication often associated with migraine and/or for those with intolerable triptan-related adverse events.Keywords: iontophoretic patch, migraine, migraine treatment, sumatriptan, transdermal patch

  8. Topical gene silencing by iontophoretic delivery of an antisense oligonucleotide-dendrimer nanocomplex: the proof of concept in a skin cancer mouse model

    Science.gov (United States)

    Venuganti, , Venkata Vamsi K.; Saraswathy, Manju; Dwivedi, Chandradhar; Kaushik, Radhey S.; Perumal, Omathanu P.

    2015-02-01

    The study was aimed at investigating the feasibility of using a poly (amidoamine) (PAMAM) dendrimer as a carrier for topical iontophoretic delivery of an antisense oligonucleotide (ASO). Bcl-2, an anti-apoptotic protein implicated in skin cancer, was used as the model target protein to demonstrate the topical gene silencing approach. Confocal laser scanning microscopy studies demonstrated that the iontophoretically delivered ASO-dendrimer complex can reach the viable epidermis in porcine skin. In contrast, passively delivered free or dendrimer complexed ASO was mainly localized to the stratum corneum. The cell uptake of ASO was significantly enhanced by the dendrimer complex and the complex suppressed Bcl-2 levels in the cell. In the skin cancer mouse model, the iontophoretically delivered ASO-dendrimer complex reduced the tumor volume by 45% and was consistent with the reduction in Bcl-2 protein levels. The iontophoretically delivered ASO-dendrimer complex caused significant apoptosis in skin tumor. Overall, the findings from this study demonstrate that dendrimers are promising nanocarriers for developing topical gene silencing approaches for skin diseases.The study was aimed at investigating the feasibility of using a poly (amidoamine) (PAMAM) dendrimer as a carrier for topical iontophoretic delivery of an antisense oligonucleotide (ASO). Bcl-2, an anti-apoptotic protein implicated in skin cancer, was used as the model target protein to demonstrate the topical gene silencing approach. Confocal laser scanning microscopy studies demonstrated that the iontophoretically delivered ASO-dendrimer complex can reach the viable epidermis in porcine skin. In contrast, passively delivered free or dendrimer complexed ASO was mainly localized to the stratum corneum. The cell uptake of ASO was significantly enhanced by the dendrimer complex and the complex suppressed Bcl-2 levels in the cell. In the skin cancer mouse model, the iontophoretically delivered ASO-dendrimer complex

  9. 交流电机离散时间电流调节器的设计%Discrete-time Current Regulator Design for AC Machine

    Institute of Scientific and Technical Information of China (English)

    杨立永; 田安民

    2011-01-01

    分析了运行在较高基频与采样频率的比值下异步电机的离散时间电流调节器的特点,该情况普遍应用在高速列车驱动和大型牵引驱动上.若电流调节器的设计不能很好地满足控制系统离散特性,在较高的基频与采样频率比值下,系统会发生严重的振荡或者不稳定响应.通过一个含SVPWM延迟的离散时域交流电机模型,设计离散时域复矢量电流调节器.仿真和实验结果证明该调节器具有非常优越的稳定性和鲁棒性,充分满足了控制系统的离散特性.%The behaviors of discrete-time current regulators for AC machines operating at high ratios of fundamental-tosampling frequencies are analyzed, a situation common for high speed automotive drives and large traction drives. When the current regulator design does not properly incorporate the effects of the discrete nature of the controller, the highly oscillatory,or unstable response can occur,at high ratios of fundamental-to-sampling frequencies. As a part of this investigation,a discrete-time domain AC machine model is developed that includes the delays associated with SVPWM. This model is used to design a discrete-time domain version of the complex vector current regulator that demonstrates improved response compared with the other regulators studied. Simulation and the experimental results prove that the complex vector peoformance indice has very superior stability and robustness, fully meets the discrete control system.

  10. High critical current of Ti-sheathed MgB{sub 2} wires for AC and weight-critical applications

    Energy Technology Data Exchange (ETDEWEB)

    Alessandrini, M; Fang, H; Hanna, M; Putman, P; Zhou, Y X; Salama, K [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-4006 (United States)

    2006-01-15

    The peculiar features of magnesium diboride make it suitable for many potential applications. In the last four years of investigation of MgB{sub 2}, the scientific community's research was mainly motivated by features such as low cost, compatibility with straightforward processing methods, relatively high critical temperature, and absence of weak links between grains. Other applications suggest the accentuation of other MgB{sub 2} properties. In particular its very low mass density makes it attractive for space activities, where the cost per kilogram for orbiting is still a huge obstacle, e.g. the cost of transport to low Earth orbit can reach 15 k$ kg{sup -1}. In order to promote the use of this compound for space activities, we tested titanium as a sheath material. Titanium is non-magnetic and its alloys are almost half the weight of steel but with yield stresses up to three times higher. We fabricated Ti-sheathed MgB{sub 2} through the powder-in-tube process. These wires show similar results to those sheathed with Fe. At 4 K the critical current density J{sub c} is well above 7 x 10{sup 5} A cm{sup -2}. The interface between the superconducting intermetallic compound and the lightweight sheath does not show any evidence of reaction and diffusion up to 900 deg. C. An analysis was carried out using x-ray diffraction, scanning electron microscopy with an energy dispersive spectrometer, and electron microprobe analysis.

  11. Surface magnetic properties of Co{sub 69}Fe{sub 4}Si{sub 15}B{sub 12} when DC and AC currents flow through the ribbon

    Energy Technology Data Exchange (ETDEWEB)

    Fal-Miyar, Vanessa [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s.n., 33007, Oviedo (Spain); Kurlyandskaya, Galina V. [Universidad del Pais Vasco UPV-EHU, Dpto. Electricidad y Electronica, Apdo. 644, 48080, Bilbao (Spain); Garcia, Jose A. [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s.n., 33007, Oviedo (Spain); Elbaile, Laura [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s.n., 33007, Oviedo (Spain)]. E-mail: elbaile@uniovi.es; Crespo, Rosario D. [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s.n., 33007, Oviedo (Spain); Tejedor, Marcos [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s.n., 33007, Oviedo (Spain)

    2006-09-15

    Surface magnetic properties of Co{sub 69}Fe{sub 4}Si{sub 15}B{sub 12} amorphous ribbons with longitudinal and transverse anisotropies when an electrical current flows through the ribbons has been studied. Observations were performed by the transverse magnetooptical Kerr effect. A DC electrical current caused a shift of the transverse hysteresis loop and AC current produced an increase of the coercive field.

  12. Single-Phase Direct AC-AC Boost Converter

    Directory of Open Access Journals (Sweden)

    LUCANU, M.

    2014-08-01

    Full Text Available The paper presents a single-phase direct AC-AC boost converter. The circuit of the converter is simple and it has good performances, irrespective of the load nature. The adequate functioning and high performance of the circuit (the efficiency and waveform of the absorbed input current were tested both by simulation and experimentally.

  13. Use of Fentanyl Iontophoretic Transdermal System (ITS) (IONSYS(®)) in the Management of Patients with Acute Postoperative Pain: A Case Series.

    Science.gov (United States)

    Poplawski, Steven; Johnson, Matthew; Philips, Philip; Eberhart, Leopold H J; Koch, Tilo; Itri, Loretta M

    2016-12-01

    Fentanyl iontophoretic transdermal system (ITS) [IONSYS(®), The Medicines Company, Parsippany, NJ, USA] is a needle-free, patient-controlled, postoperative opioid pain management treatment. It is indicated for the short-term management of acute postoperative pain in adults requiring opioid analgesia in the hospital. The safety and effectiveness of fentanyl ITS for acute postoperative pain management has been demonstrated in a range of surgery and patient types studied in seven phase 3 trials (three placebo-controlled trials and four active-comparator trials). The majority of the patients in the phase 3 trials had undergone either abdominal/pelvic, orthopedic, or thoracic surgery. Consistent with the prescribing information, physicians in clinical practice may treat patients with this system following any type of surgery including those that may not have been included in the phase 3 trials. The purpose of this case series is to illustrate how fentanyl ITS is being utilized for postoperative pain management in real-world clinical practice following a variety of surgeries and in current pain management protocols that may have evolved since the completion of the phase 3 program. There are seven cases from three clinical centers described within this case series, each using fentanyl ITS according to the prescribing information. The surgery types included are bariatric (N = 3), prostate (N = 2), colorectal (N = 1), and perirectal abscess drainage (N = 1). A systematic review of each patient chart was conducted via a standardized retrospective assessment by the clinicians who managed each patient. Additionally, each healthcare professional was interviewed regarding their overall experience and key learnings using fentanyl ITS. Overall, fentanyl ITS was effective and well tolerated in these case reports in current-day clinical practice settings. These case studies are informative about fentanyl ITS use shortly after product approval and set the stage for

  14. Enhanced Cancer Cell (HeLa Killing Efficacy of Mixed Αlpha and Gamma Iron Oxide Superparamagnetic Nanoparticles under Combined AC (Alternating Current Magnetic-Field and Photoexcitation

    Directory of Open Access Journals (Sweden)

    Md. Shariful Islam, Yoshihumi Kusumoto, Md. Abdulla Al-Mamun and Yuji Horie

    2011-12-01

    Full Text Available We synthesized mixed α and γ-Fe2O3 nanoparticles and investigated their toxic effects against HeLa cells under induced AC (alternating current magnetic-fields and photoexcited conditions at room temperature. The findings revealed that the cell-killing percentage was increased with increasing dose for all types of treatments. Finally, 99% cancer cells were destructed at 1.2 mL dose when exposed to combined AC magnetic-field and photoexcited conditions (T3 whereas 89 and 83 % of HeLa cells were killed under only AC magnetic-field induced (T1 or only photoexcited (T2 condition at the same dose.ABSTRAK: Campuran α dan zarah γ-Fe2O3 bersaiz nano disintesiskan dan kesan toksidnya terhadap sel HeLa dikaji dibawah aruhan medan magnet arus ulang-alik (alternating current (AC dan keadaan photoexcited (proses ransangan atom atau molekul suatu bahan dengan penyerapan tenaga sinaran pada suhu bilik. Penemuan mendedahkan bahawa peratusan sel yang musnah bertambah dengan pertambahan dos untuk semua jenis rawatan. Akhirnya, 99% sel kanser dimusnahkan pada kadar dos 1.2mL setelah didedahkan terhadap kombinasi medan magnet AC dan keadaan photoexcited (T3 dimana 89% dan 83% sel HeLa dimusnahkan dengan hanya di bawah aruhan medan magnet AC (T1 atau hanya pada keadaan photoexcited (T2 pada kadar dos yang sama.KEY WORDS : Cancer, Hyperthermia, Iron oxide nanoparticles, Heat dissipation,    Cytotoxicity, HeLa cell.

  15. Tevatron AC dipole system

    Energy Technology Data Exchange (ETDEWEB)

    Miyamoto, R.; Kopp, S.E.; /Texas U.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.

  16. Development of the fentanyl iontophoretic transdermal system (ITS) for patient-controlled analgesia of postoperative pain management.

    Science.gov (United States)

    Minkowitz, Harold S; Danesi, Hassan; Ding, Li; Jones, James B

    2015-09-01

    The fentanyl iontophoretic transdermal system (ITS) is a needle-free, patient-activated drug delivery system used for patient-controlled analgesia in adult hospitalized patients with postoperative pain. The system design has been updated to a separated system consisting of a Controller and a Drug Unit, and has had regulatory submissions in USA and Europe in 2014. Fentanyl ITS has been shown to be therapeutically equivalent to morphine intravenous (iv.) patient-controlled analgesia. One of the advantages of fentanyl ITS is that patients have better mobility as there is no need for an iv. pump, iv. lines and pole. The introduction of the updated fentanyl ITS will add a versatile tool to the postoperative pain management armamentarium.

  17. THE INFLUENCE OF CONDUCTOR LAYER CURRENT SHARING CHARACTERISTIC ON AC LOSSES OF COLD DIELECTRIC HTS CABLE%导电层分流特征对高温超导电缆交流损耗影响

    Institute of Scientific and Technical Information of China (English)

    夏占军; 诸嘉慧; 郭立杰; 马学良; 张晓颖; 赵瑞

    2012-01-01

    为了分析导电层分流特征对超导电缆交流损耗分布影响,建立了基于YBCO涂层导体的110kV/3kA冷绝缘高温超导电缆载流数学模型,计算了不同运行温度下超导电缆各导电层电流分布,并根据Monoblock模型及Bean模型计算了超导电缆交流损耗.计算结果表明77K下超导电缆层电流均匀分布时总交流损耗最小;69K时超导电缆总交流损耗最小时,电缆各导电层电流分布不均,超导电缆层电流均匀分布时总交流损耗最小这一观点并不具有普遍性.所提出的计算方法和结果为降低多导电层超导电缆交流损耗提供了新思路.%To analyze the influence of conductor layer current sharing characteristic on AC losses of the High Temperature Superconducting (HTS) cable,the mathematical model of 110kV/3kA cold dielectric (CD) HTS cable based on YBCO coated conductor is set up and also the layer current distribution is calculated. The AC losses of the HTS cable are calculated by Monoblock model and Bean model. Results Show that the uniform layer current distribution can lead to the minimum total AC losses of the HTS cable at 77K. But at 69k the minimum total AC losses were not obtained at the condition of uniform layer current distribution. So the view of the uniform layer current distribution gives the minimum total AC losses of the HTS cable does not have catholicity, this result provide a new idea for reducing AC losses of multilayer HTS cable.

  18. Evaluation of a Modified High-Definition Electrode Montage for Transcranial Alternating Current Stimulation (tACS) of Pre-Central Areas

    DEFF Research Database (Denmark)

    Heise, Kirstin Friederike; Kortzorg, Nick; Saturnino, Guilherme Bicalho;

    2016-01-01

    Objective: To evaluate a modified electrode montage with respect to its effect on tACS-dependent modulation of corticospinal excitability and discomfort caused by neurosensory side effects accompanying stimulation. Methods: In a double-blind cross-over design, the classical electrode montage...... random noise stimulation). Results: Corticospinal excitability increased significantly during and immediately after tACS with the centre-ring montage. This was not the case with the classical montage or tRNS stimulation. Level of discomfort was rated on average lower with the centre-ring montage....... Conclusions: In comparison to the classic montage, the M1 centre-ring montage enables a more focal stimulation of the target area and, at the same time, significantly reduces neurosensory side effects, essential for placebo-controlled study designs....

  19. A Phase I, Open-Label, Single-Dose Safety, Pharmacokinetic, and Tolerability Study of the Sumatriptan Iontophoretic Transdermal System in Adolescent Migraine Patients.

    Science.gov (United States)

    Gutman, Dikla; Hellriegel, Edward; Aycardi, Ernesto; Bigal, Marcelo E; Kunta, Jeevan; Chitra, Rohini; Kansagra, Sujay; Kidron, Orna Srur; Knebel, Helena; Linder, Steven; Ma, Yuju; Pierce, Mark; Winner, Paul K; Spiegelstein, Ofer

    2016-09-01

    To evaluate the safety, tolerability, and pharmacokinetics of sumatriptan delivered by the iontophoretic transdermal system (TDS) in adolescent patients. Since nausea can be a prominent and early symptom of migraine, nonoral treatment options are often required. Sumatriptan iontophoretic TDS is approved for the acute treatment of migraine in adults. The present study evaluates the pharmacokinetics of sumatriptan administered via the iontophoretic TDS in adolescents, contrasting the findings with historical data from adults. Patients aged 12-17 years (inclusive) with acute migraine were treated with sumatriptan iontophoretic TDS for 4 hours. Blood samples for pharmacokinetic profiling of sumatriptan were obtained prior to dosing and at predetermined time points covering the 12 hours postonset of treatment. Key pharmacokinetic endpoints included Cmax (peak plasma drug concentration), tmax (time to Cmax ), AUC0-∞ (area under the plasma concentration-time curve from time 0 to infinity), and t½ (terminal elimination half-life). Safety was evaluated by monitoring of adverse events in addition to laboratory and clinical assessments. The sample consisted of 37 patients, and 36 were included in the PK evaluable population. Cmax , tmax , AUC0-∞ , and t½ values were all similar between male and female patients and between younger (12-14 years) and older (15-17 years) adolescents. When compared with historical adult data, adolescent patients demonstrated similar systemic exposures to those observed in adults (mean Cmax 20.20 (±6.43) ng/mL in adolescents vs 21.89 (±6.15) ng/mL in adults; mean AUC0-∞ 98.1 (±28.1) ng·h/mL in adolescents vs 109.7 (±26.1) ng·h/mL in adults). All adverse events were mild or moderate, with application-site paresthesia being the most common (32%). No clinically relevant changes in laboratory values, vital signs, or electrocardiogram findings were observed. The iontophoretic TDS produced mean systemic exposures to sumatriptan in younger

  20. Water versus salty taste and Iontophoretic ANGII responses of septopreoptic neurons in dehydrated and euhydrated awake rats.

    Science.gov (United States)

    Mousseau, M C; Thornton, S N; Liénard, F; Martial, F P; Nicolaïdis, S

    1996-01-01

    Little is known of the influence of gustatory, particularly salt, input on neurons of the forebrain and if the same neurons are sensitive to hydromineral balance humoral stimuli. In awake, nonpremedicated rats we recorded the activity of spontaneously active neurons in the preoptic/anterior hypothalamic area of dehydrated and euhydrated rats while allowing them to ingest water or a hypertonic salt solution (1.6% NaCl) administered to the tongue. The hormones angiotensin and aldosterone, both implicated in hydromineral balance, were applied by iontophoresis to the same neurons. In the dehydrated rats, 27% (15/55) of the spontaneously active neurons responded to a liquid (either water or the NaCl) applied to the tongue; in the euhydrated rats 23% (18/78) responded to the same stimuli. In the dehydrated rats, however, 33% (5/15) of the responding neurons were inhibited when the NaCl solution was applied to the tongue compared with only 5% (1/18) in the euhydrated rats. Iontophoretic application of angiotensin increased the spontaneous activity in 21% of those neurons tested that responded to taste. These results suggest that the state of hydration of an animal is able to change the neuronal response to substances applied to the tongue. Furthermore, it appears that these gustatory-sensitive neurons may also be related to hydromineral balance regulation since they are able to respond to angiotensin.

  1. AC 410 AC410 AC410 Unit 7 Homework Assignment

    OpenAIRE

    Laynebaril1

    2017-01-01

    AC 410 AC410 AC410 Unit 7 Homework Assignment Click Link Below To Buy: http://hwcampus.com/shop/ac410-unit-7-homework-assignment/    Questions Requiring Analysis 14-30   Early in your first audit of Star Corporation, you notice that sales and year-end inventory are almost unchanged from the prior year. However, cost of goods sold is less than in the preceding year, and accounts payable also are down substantially. Gross profit has increased, but this increase has not c...

  2. AC Electrokinetics of Physiological Fluids for Biomedical Applications.

    Science.gov (United States)

    Lu, Yi; Liu, Tingting; Lamanda, Ariana C; Sin, Mandy L Y; Gau, Vincent; Liao, Joseph C; Wong, Pak Kin

    2015-12-01

    Alternating current (AC) electrokinetics is a collection of processes for manipulating bulk fluid mass and embedded objects with AC electric fields. The ability of AC electrokinetics to implement the major microfluidic operations, such as pumping, mixing, concentration, and separation, makes it possible to develop integrated systems for clinical diagnostics in nontraditional health care settings. The high conductivity of physiological fluids presents new challenges and opportunities for AC electrokinetics-based diagnostic systems. In this review, AC electrokinetic phenomena in conductive physiological fluids are described followed by a review of the basic microfluidic operations and the recent biomedical applications of AC electrokinetics. The future prospects of AC electrokinetics for clinical diagnostics are presented.

  3. Calculation and Analysis of DC Link Capacitor's Current for AC-DC-AC Inverter%AC—DC—AC变频器直流支撑电容电流计算及分析

    Institute of Scientific and Technical Information of China (English)

    刘海涛; 陈涛

    2012-01-01

    In order to guarantee the performance of converter, it needs to select the appropriate intermediate DC support capacitor. According to the analysis of the circuit topology and the switch modulation mode of converter and referring to the existing literature, it summerizes a method to calculate current of the capacitor. The theory and simulation results demonstrate that this method has good accuracy.%为了使变频器满足性能要求,需选择合适的中间直流支撑电容。根据对变频器电路拓扑与开关调制方式的分析,并借鉴已有文献资料,归纳出计算电容器电流的方法。理论与仿真证明,该方法有较好的准确性。

  4. Guiding Principles in Selecting AC To DC Converters For Power Factor Corrections in AC Transmission System

    Directory of Open Access Journals (Sweden)

    Ibekwe B.E

    2014-10-01

    Full Text Available The ac to dc converters’ power factors correction in ac transmission system were investigated. The studies include: phase-controlled converter; pulse width modulated (PWM converter and ac input current shaped converter. Using Fourier series, power factors of these converters were calculated and simulated using MATLAB. The resulting curves are displayed in the hard copies for practical guides in the choice of converters; and comparatively, current shaped type is the best.

  5. 基于垂直引线和调制电流的三线环形磁导引%Three wire toroidal magnetic guide based on the vertical leads and ac current mo dulation

    Institute of Scientific and Technical Information of China (English)

    程俊; 张敬芳; 许忻平; 蒋小军; 李晓林; 张海潮; 王育竹

    2016-01-01

    A new scheme to create a closed toroidal magnetic waveguide for deBroglie wave on a single layer atom chip is proposed and there is no zero magnetic field along the guide center. The guide is a two-dimensional magnetic trap for trapping weak-field seeking states of atoms with a magnetic dipole moment. The designed wire structure on the atom chip consists of three concentric and isometric ring wires, and six vertical current leads of the three ring wires. By using the through silicon via technology, the current leads can be made perpendicular to the atom chip surface instead of being generally arranged side by side on the chip surface. Compared with the general wiring way, the vertical lead way has two advantages. One is that each ring wire gap caused by the current leads is substantially smaller than the distance between the ring wires, which permits the generation of a closed toroidal magnetic guide near the atom chip surface when dc currents are supplied to the three ring wires. The other is that the distance between two leads of each ring wire is considerably reduced, resulting in the fact that the magnetic perturbation of the leads to the whole toroidal magnetic guide is negligible. We numerically calculate the magnetic field distribution generated by our wire layout when dc currents are applied, and it is shown that a closed and tight toroidal magnetic guide is formed near the atom chip surface. However, there are zero magnetic fields existing along the center of the toroidal guide, which leads to Majorana spin flips from trapped magnetic substate to an un-trapped magnetic sub-state. According to the time-orbiting-potential principle, we propose an ac current modulation method, which is simple and stable, to reduce the atom losses and suppress the atomic decoherence in the toroidal magnetic guide. We deduce the ac current expressions for the case of three isometric infinite straight wires and apply the ac modulation current expressions directly to our three

  6. AC Optimal Power Flow

    Energy Technology Data Exchange (ETDEWEB)

    2016-10-04

    In this work, we have implemented and developed the simulation software to implement the mathematical model of an AC Optimal Power Flow (OPF) problem. The objective function is to minimize the total cost of generation subject to constraints of node power balance (both real and reactive) and line power flow limits (MW, MVAr, and MVA). We have currently implemented the polar coordinate version of the problem. In the present work, we have used the optimization solver, Knitro (proprietary and not included in this software) to solve the problem and we have kept option for both the native numerical derivative evaluation (working satisfactorily now) as well as for analytical formulas corresponding to the derivatives being provided to Knitro (currently, in the debugging stage). Since the AC OPF is a highly non-convex optimization problem, we have also kept the option for a multistart solution. All of these can be decided by the user during run-time in an interactive manner. The software has been developed in C++ programming language, running with GCC compiler on a Linux machine. We have tested for satisfactory results against Matpower for the IEEE 14 bus system.

  7. La fermentation acétonobutylique. Synthèse bibliographique et orientations actuelles Butanol-Acetone Fermentation. Bibliographie Synthesis and Current Trends

    Directory of Open Access Journals (Sweden)

    Marchal R.

    2006-11-01

    Full Text Available Cet article présente une synthèse des connaissances sur la fermentation acétonobutylique tant d'un point de vue microbiologique que technologique. Divers aspects du métabolisme et de la régulation du microorganisme mis en oeuvre sont abordés. Les performances de la fermentation sur ses substrats traditionnels (farine de maïs ou mélasses sont comparées avec celles qui ont été récemment obtenues à partir du topinambour à l'Institut Français du Pétrole, dans le cadre d'un nouveau développement de cette fermentation pour la production de carburants. This article gives a synthesis of what is known about butylacetone fermentation from both the microbiological and technological standpoints. Different aspects of the metabolism of the microorganism used and of how it is regulated are considered. The performances of fermentation on traditional substrates (cornmeal or molasses are compared with those recently obtained using Jerusalem artichokes at Institut Français du Pétrole as part of a new project on this fermentation for the purpose of producing substitute fuel.

  8. A/C轴双摆角铣头发展现状与关键技术%Current situation and key technologies of A/C axes bi-rotary milling head

    Institute of Scientific and Technical Information of China (English)

    李焱; 高秀烽; 刘春时; 林剑峰; 徐吉存; 化春雷

    2011-01-01

    A/C axes bi-rotary milling head is one of the most important functional components of middle and large dimensional gantry type five-axis machining centers.Current situation of A/C axes bi-rotary milling head at home and abroad is analyzed,and the technology gap between the existing domestic level and the world's advanced level is pointed out,and key technologies of A/C axes bi-rotary milling head including direct drive technology,gap eliminating of mechanical transmission backlash technology, clamping and positioning technology as well as A axis automatic exchange technology,measurement and compensation of geometric errors technology are illustrated in detail, which will play an important role in research and design of A/C axes bi-rotary milling head in our country in the future.%A/C轴双摆角铣头是中、大规格龙门式五轴联动加工中心的关键功能部件.分析了国内外A/C轴双摆角铣头的发展现状,指出了国内现有水平与世界先进水平的技术差距,并详细阐述了该类产品的关键技术,主要包括直驱技术、机械传动消隙技术、旋转轴夹紧定位技术、A轴自动交换技术,几何误差检测与补偿技术,详细阐述了各个关键技术的技术特点以及在A/C轴双摆角铣头中的应用方法,对我国A/C轴双摆角铣头今后的研发工作起到了重要的推动作用与借鉴意义.

  9. Differential effects of petit mal anticonvulsants and convulsants on thalamic neurones: GABA current blockade.

    OpenAIRE

    COULTER, D. A.; Huguenard, J. R.; PRINCE, D. A.

    1990-01-01

    1. Currents evoked by applications of gamma-aminobutyric acid (GABA) to acutely dissociated thalamic neurones were analysed by voltage-clamp techniques, and the effects of the anticonvulsant succinimides ethosuximide (ES) and alpha-methyl-alpha-phenylsuccinimide (MPS) and the convulsants tetramethylsuccinimide (TMS), picrotoxin, pentylenetetrazol (PTZ), and bicuculline methiodide were assessed. 2. TMS (1 microM-10 microM) reduced responses to iontophoretically applied GABA, as did picrotoxin ...

  10. Peltier ac calorimeter

    OpenAIRE

    Jung, D. H.; Moon, I. K.; Jeong, Y. H.

    2001-01-01

    A new ac calorimeter, utilizing the Peltier effect of a thermocouple junction as an ac power source, is described. This Peltier ac calorimeter allows to measure the absolute value of heat capacity of small solid samples with sub-milligrams of mass. The calorimeter can also be used as a dynamic one with a dynamic range of several decades at low frequencies.

  11. SINGLE PHASE HIGH FREQUENCY AC CONVERTER FOR INDUCTION HEATING APPLICATION

    Directory of Open Access Journals (Sweden)

    M.A INAYATHULLAAH,

    2010-12-01

    Full Text Available The proposed topology reduces the total harmonic distortion (THD of a high frequency AC/AC Converter well below the acceptable limit. This paper deals with a novel single phase AC/DC/AC soft switching utility frequency AC to high frequency AC converter. In this paper a single phase full bridge inverter with Vienna rectifier as front end is used instead of conventional diode bridge rectifier to provide continuous sinusoidal input current with nearly unity power factor at the source side with extremely low distortion.. This power converter is more suitable and acceptable for cost effective high frequency (HF consumer induction heating applications.

  12. A chopper current-feedback instrumentation amplifier with a 1 mHz 1/f noise corner and an AC-coupled ripple reduction loop

    NARCIS (Netherlands)

    Wu, R.; Makinwa, K.A.A.; Huijsing, J.H.

    2009-01-01

    This paper presents a chopper instrumentation amplifier for interfacing precision thermistor bridges. For high CMRR and DC gain, the amplifier employs a three-stage current-feedback topology with nested-Miller compensation. By chopping both the input and intermediate stages of the amplifier, a 1 mHz

  13. RHIC spin flipper AC dipole controller

    Energy Technology Data Exchange (ETDEWEB)

    Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.

    2011-03-28

    The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.

  14. The Effect of the Feedback Controller on Superconducting Tokamak AC Losses + AC-CRPP user manual

    Energy Technology Data Exchange (ETDEWEB)

    Schaerz, B.; Bruzzone, P.; Favez, J.Y.; Lister, J.B.; Zapretilina, E

    2001-11-01

    Superconducting coils in a Tokamak are subject to AC losses when the field transverse to the coil current varies. A simple model to evaluate the AC losses has been derived and benchmarked against a complete model used in the ITER design procedure. The influence of the feedback control strategy on the AC losses is examined using this model. An improved controller is proposed, based on this study. (author)

  15. ACAC Converters for UPS

    Directory of Open Access Journals (Sweden)

    Rusalin Lucian R. Păun

    2008-05-01

    Full Text Available This paper propose a new control technique forsingle – phase ACAC converters used for a on-line UPSwith a good dynamic response, a reduced-partscomponents, a good output characteristic, a good powerfactorcorrection(PFC. This converter no needs anisolation transformer. A power factor correction rectifierand an inverter with the proposed control scheme has beendesigned and simulated using Caspoc2007, validating theconcept.

  16. Time Resolved Magneto-Optical Imaging in High Frequency AC Currents of YBa2Cu3O7-delta Thin Films (Postprint)

    Science.gov (United States)

    2012-02-01

    resolved imaging, we use a Q- switched Nd:YLF diode-pumped solid-state laser which provides 100-nsec short pulses at 527-nm wavelength. The pulse...We use a 6-µm thick epitaxial grown ferrite -garnet film (FGF) (Y,Bi,Pr,Lu)3.0(Fe,Ga)5.0O12.0 with an in-plane magnetization as the MO indicator...sub-nanoseconds by the magnetization switching time of the FGF as in ref. [11]. The power source provides up to 15 Amps of bipolar current in a

  17. Critical current density and ac harmonic voltage generation in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films by the screening technique

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lopez, Israel O., E-mail: iperez@mda.cinvestav.m [Applied Physics Department, Cinvestav Unidad Merida, Km 6 Ant., Carretera a Progreso, A.P. 73, C.P. 97310 Merida, Yucatan (Mexico); Gamboa, Fidel; Sosa, Victor [Applied Physics Department, Cinvestav Unidad Merida, Km 6 Ant., Carretera a Progreso, A.P. 73, C.P. 97310 Merida, Yucatan (Mexico)

    2010-12-15

    The temperature and field dependence of harmonics in voltage V{sub n}=V{sub n}{sup '}-iV{sub n}{sup ''} using the screening technique have been measured for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting thin films. Using the Sun model we obtained the curves for the temperature-dependent critical current density J{sub c}(T). In addition, we applied the criterion proposed by Acosta et al. to compute J{sub c}(T). Also, we made used of the empirical law J{sub c{proportional_to}}(1-T/T{sub c}){sup n} as an input in our calculations to reproduce experimental harmonic generation up to the fifth harmonic. We found that most models fit well the fundamental voltage but higher harmonics are poorly reproduced. Such behavior suggests the idea that higher harmonics contain information concerning complex processes like flux creep or thermally assisted flux flow.

  18. ACS: ALMA Common Software

    Science.gov (United States)

    Chiozzi, Gianluca; Šekoranja, Matej

    2013-02-01

    ALMA Common Software (ACS) provides a software infrastructure common to all ALMA partners and consists of a documented collection of common patterns and components which implement those patterns. The heart of ACS is based on a distributed Component-Container model, with ACS Components implemented as CORBA objects in any of the supported programming languages. ACS provides common CORBA-based services such as logging, error and alarm management, configuration database and lifecycle management. Although designed for ALMA, ACS can and is being used in other control systems and distributed software projects, since it implements proven design patterns using state of the art, reliable technology. It also allows, through the use of well-known standard constructs and components, that other team members whom are not authors of ACS easily understand the architecture of software modules, making maintenance affordable even on a very large project.

  19. Critical current densities of Sr{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2} superconductors estimated from AC susceptibilities

    Energy Technology Data Exchange (ETDEWEB)

    Setoyama, Subaru; Kinoshita, Junichi; Akune, Tadahiro [Department of Electrical Engineering and Information Technology, Kyushu Sangyo Univ., 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan); Sakamoto, Nobuyoshi, E-mail: saka@te.kyusan-u.ac.jp [Department of Electrical Engineering and Information Technology, Kyushu Sangyo Univ., 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan); Murakami, Kouji; Yoshida, Nobuyuki [Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka 820-8502 (Japan); Kiuchi, Masaru; Otabe, Edmund Soji [Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka 820-8502 (Japan); JST–TRIP, 5 Sanban, 102-0075 Tokyo (Japan); Matsushita, Teruo [Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka 820-8502 (Japan); Ge, Jun [Department of Life, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka 811-0295 (Japan); Ni, Baorong [Department of Life, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka 811-0295 (Japan); JST–TRIP, 5 Sanban, 102-0075 Tokyo (Japan); Wang, Lei; Qi, Yanpeng; Zhang, Xianping; Gao, Zhaoshun; Ma, Yanwei [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China)

    2013-01-15

    Highlights: ► Effect of Ag addition on SrKFeAs (122 type) superconductors are examined by the grained Bean model. ► Critical current densities and their temperature and field dependence in the grains J{sub cg} and the link J{sub cℓ} are estimated. ► The J{sub cℓ} ’s of Ag-added sample are field independent and 7–9 times larger. -- Abstract: AC susceptibilities (real χ′ and imaginary χ″) of Sr{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2} (122 type) polycrystalline with Ag addition are analysed by the grained Bean model. A variety of characteristics, double peak in χ″ and shoulder transition in χ′, appear in the model simulation. Comparing the measured χ′ and χ″ with the model allows more clear insight on the polycrystalline structure. Estimated critical current densities J{sub cg} and J{sub cℓ} of the grain and the link in the iron-based pnictides show that the addition of 20 wt.% Ag increases J{sub cℓ} 9 times larger. Improvement of intergrain characteristics with Ag addition is clearly indicated.

  20. AC Short-Circuit Current Calculation Scheme Based on Parameter Optimization%基于参数优化的交流系统短路电流计算方案

    Institute of Scientific and Technical Information of China (English)

    张帆; 赵勇; 苏寅生; 李智欢; 杨银国

    2015-01-01

    In view of unreasonable and even often optimistic assessment of power system short-circuit current, based on analysis of basic principles of AC short-circuit current calculation, from the perspective of result modification, a set of short-circuit current calcu-lation scheme is provided. Firstly, a linear modification formula to calculate the short-circuit current, including the coefficient of cur-rent correction K and the deviation of current ΔI is given;and then the optimization principles and the objective function for determi-ning the above two parameters based on actual short-circuit faults are proposed, which can promise the calculating results with high precision under the premise of not lower than measured values. Application of this scheme to actual short-circuit current evaluation of CSG reveals that, compared with existing schemes, the proposed scheme promises the results with conservation and precision, and can be regarded as an effective supplement for short-circuit current calculating tools.%针对目前电力系统短路电流水平评估不合理甚至经常偏乐观的情况, 基于对交流系统短路电流计算基本原理的分析, 从计算结果修正的角度提出了一套短路电流计算方案. 首先提出了包含电流修正系数K和电流偏差修正量ΔI的短路电流线性修正公式; 然后给出了基于电网实际故障确定这两个参数的寻优原则和目标函数, 保证短路电流计算值在不低于实测值的前提下仍具有较高的精度. 针对南方电网实际短路故障的应用结果表明, 相比于已有的短路电流计算方案, 所提出的计算方案合理有效, 在评估系统短路电流水平时能兼具保守性和准确性, 是对现有短路电流计算工具的有效补充.

  1. Operation of AC Adapters Visualized Using Light-Emitting Diodes

    Science.gov (United States)

    Regester, Jeffrey

    2016-01-01

    A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

  2. Temperature dependence of critical currents and ac transport losses in (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and YBa{sub 2}Cu{sub 3}O{sub y} tapes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guo Min [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Knoll, D C [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Nguyen, D N [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Sastry, P V P S S [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Schwartz, Justin [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States)

    2007-06-15

    The critical currents and self-field ac losses of YBa{sub 2}Cu{sub 3}O{sub y} coated conductors and (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} tapes were measured at several temperatures between 45 K and the respective critical temperature. The temperature dependence of ac losses was measured at 50 Hz using the lock-in method for a transport current. The frequency dependence of ac loss was measured at 55 K for transport current frequencies from 25 to 400 Hz. The results show that variation of ac transport loss as a function of normalized critical current is nearly the same at all temperatures in the measured temperature range for both YBa{sub 2}Cu{sub 3}O{sub y} and (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} tapes. The temperature dependence of the loss factor, however, is different for (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and YBa{sub 2}Cu{sub 3}O{sub y} tapes because of the ferromagnetic loss in the NiW-based coated conductor substrate. Similarities and differences in the temperature and frequency dependence of ac transport losses between (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and YBa{sub 2}Cu{sub 3}O{sub y} tapes are discussed.

  3. AcEST: DK950971 [AcEST

    Lifescience Database Archive (English)

    Full Text Available GN=... 37 0.66 tr|B1ACS4|B1ACS4_BALBO DMP1 (Fragment) OS=Balaenoptera borealis ... 37 0.66 tr|B1ACS3|B1ACS3...todon GN=DM... 37 1.1 tr|B1ACT4|B1ACT4_LISBO DMP1 (Fragment) OS=Lissodelphis borealis ... 37 1.1 tr|B1ACS2|B...SSSEEEIQSKNTEMESRRLTVDAY 160 >tr|B1ACS4|B1ACS4_BALBO DMP1 (Fragment) OS=Balaenoptera borealis GN=DMP1 PE=4 S

  4. Isolation of sequences flanking Ac insertion sites by Ac casting.

    Science.gov (United States)

    Wang, Dafang; Peterson, Thomas

    2013-01-01

    Localizing Ac insertions is a fundamental task in studying Ac-induced mutation and chromosomal rearrangements involving Ac elements. Researchers may sometimes be faced with the situation in which the sequence flanking one side of an Ac/Ds element is known, but the other flank is unknown. Or, a researcher may have a small sequence surrounding the Ac/Ds insertion site and needs to obtain additional flanking genomic sequences. One way to rapidly clone unknown Ac/Ds flanking sequences is via a PCR-based method termed Ac casting. This approach utilizes the somatic transposition activity of Ac during plant development, and provides an efficient means for short-range genome walking. Here we describe the principle of Ac casting, and show how it can be applied to isolate Ac macrotransposon insertion sites.

  5. Transcutaneous iontophoretic delivery of STAT3 siRNA using layer-by-layer chitosan coated gold nanoparticles to treat melanoma.

    Science.gov (United States)

    Labala, Suman; Jose, Anup; Venuganti, Venkata Vamsi Krishna

    2016-10-01

    Overexpression of signal transducer and activator of transcription 3 (STAT3) protein prevents apoptosis and enhances proliferation of melanocytes. The aim of this study was to investigate the feasibility of using layer-by-layer assembled gold nanoparticles (LbL-AuNP) as a carrier for iontophoretic delivery of STAT3 siRNA to treat melanoma. Chitosan coated AuNP (AuNP-CS) were prepared by direct reduction of HAuCl4 in the presence of chitosan. The AuNP-CS were then sequentially layered with siRNA and chitosan to form AuNP-CS/siRNA/CS. STAT3 siRNA replaced with scrambled siRNA or sodium alginate were used as controls. The average particle size and zeta-potential of the prepared LbL-AuNP were 150±10nm (PDI: 0.41±0.06) and 35±6mV, respectively. In vitro studies in B16F10 murine melanoma cells showed that AuNP-CS/siRNA/CS inhibited the cell growth by 49.0±0.6% and 66.0±0.2% at 0.25nM and 0.5nM STAT3 siRNA concentration, respectively. Fluorescence microscopy and flow cytometry studies showed a time dependent cell uptake of the LbL-AuNP up to 120min. Clathrin mediated endocytosis was found to be the predominant cell uptake mechanism for LbL-AuNP. STAT3 siRNA loaded LbL-AuNP reduced the STAT3 protein expression by 47.3% in B16F10 cells. Similarly, apoptosis assay showed 29% and 44% of early and late apoptotic events, respectively after treatment with STAT3 siRNA loaded LbL-AuNP. Confocal microscope and skin cryosections showed that application of 0.47mA/cm(2) of anodal iontophoresis enhanced the skin penetration of LbL-AuNP to reach viable epidermis. In conclusion, layer-by-layer chitosan coated AuNP can be developed as a carrier for iontophoretic delivery of STAT3 siRNA to treat melanoma.

  6. Transport AC Losses in Striated YBCO Coated Conductors (Postprint)

    Science.gov (United States)

    2012-02-01

    AFRL-RZ-WP-TP-2012-0124 TRANSPORT AC LOSSES IN STRIATED YBCO COATED CONDUCTORS (POSTPRINT) G.A. Levin and P.N. Barnes Mechanical Energy...TRANSPORT AC LOSSES IN STRIATED YBCO COATED CONDUCTORS (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...2006. 14. ABSTRACT DC current-voltage characteristics and transport ac losses of striated and non-striated Y1Ba2Cu3O7-δ ( YBCO ) coated conductors

  7. AC Losses of Prototype HTS Transmission Cables

    Energy Technology Data Exchange (ETDEWEB)

    Demko, J.A.; Dresner, L.; Hughey, R.L.; Lue, J.W.; Olsen, S.K.; Sinha, U.; Tolbert, J.C.

    1998-09-13

    Since 1995 Southwire Company and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested nine, l-m long, high temperature superconducting (HTS) transmission cable prototypes. This paper summarizes the AC loss measurements of five of the cables not reported elsewhere, and compares the losses with each other and with theory developed by Dresner. Losses were measured with both a calorimetric and an electrical technique. Because of the broad resistive transition of the HTS tapes, the cables can be operated stably beyond their critical currents. The AC losses were measured in this region as well as below critical currents. Dresner's theory takes into account the broad resistive transition of the HTS tapes and calculates the AC losses both below and above the critical current. The two sets of AC 10SS data agree with each other and with the theory quite welL In particular, at low currents of incomplete penetration, the loss data agree with the theoretical prediction of hysteresis loss based on only the outer two Iayers carrying the total current.

  8. AC-3 audio coder

    Science.gov (United States)

    Todd, Craig

    1995-12-01

    AC-3 is a system for coding up to 5.1 channels of audio into a low bit-rate data stream. High quality may be obtained with compression ratios approaching 12-1 for multichannel audio programs. The high compression ratio is achieved by methods which do not increase decoder memory, and thus cost. The methods employed include: the transmission of a high frequency resolution spectral envelope; and a novel forward/backward adaptive bit allocation algorithm. In order to satisfy practical requirements of an emissions coder, the AC-3 syntax includes a number of features useful to broadcasters and consumers. These features include: loudness uniformity between programs; dynamic range control; and broadcaster control of downmix coefficients. The AC-3 coder has been formally selected for inclusion of the U.S. HDTV broadcast standard, and has been informally selected for several additional applications.

  9. Cyclotron and linac production of Ac-225.

    Science.gov (United States)

    Melville, Graeme; Allen, Barry J

    2009-04-01

    Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. The reduction of radium by photonuclear transmutation by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) has been investigated. A linac dose of 2800 Gy produced about 2.4 MBq (64 microCi) of Ra-225, which decays to Ac-225 and can then be used for 'Targeted Alpha Therapy' (TAT) of cancer. This result, while consistent with theoretical calculations, is far too low to be of practical use unless much larger quantities of radium are irradiated. The increasing application of Ac-225 for cancer therapy indicates the potential need for its increased production and availability. This paper investigates the possibility of producing of Ac-225 in commercial quantities, which could potentially reduce obsolete radioactive material and displace the need for expensive importation of Ac-225 from the USA and Russia in the years ahead. Scaled up production of Ac-225 could theoretically be achieved by the use of a high current cyclotron or linac. Production specifications are determined for a linac in terms of current, pulse length and frequency, as well as an examination of other factors such as radiation issues and radionuclei separation. Yields are compared with those calculated for the Australian National Cyclotron in Sydney.

  10. System and method for determining stator winding resistance in an AC motor using motor drives

    Science.gov (United States)

    Lu, Bin; Habetler, Thomas G; Zhang, Pinjia

    2013-02-26

    A system and method for determining the stator winding resistance of AC motors is provided. The system includes an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, a pulse width modulation (PWM) converter having switches therein to control current flow and terminal voltages in the AC motor, and a control system connected to the PWM converter. The control system generates a command signal to cause the PWM converter to control an output of the AC motor drive corresponding to an input to the AC motor, selectively generates a modified command signal to cause the PWM converter to inject a DC signal into the output of the AC motor drive, and determines a stator winding resistance of the AC motor based on the DC signal of at least one of the voltage and current.

  11. Flexible AC transmission systems: the state of the art

    Energy Technology Data Exchange (ETDEWEB)

    Edris, Abdel-Aty [Electric Power Research Inst., Palo Alto, CA (United States). Electric Systems Division

    1994-12-31

    Flexible AC transmission systems (FACTS) is a concept promoting the use of power electronic controllers to enhance the controllability and usable capacity of AC transmission. This paper presents the state of the art of FACTS and the status of the current projects for the application of the FACTS controllers in transmission systems. (author) 8 refs., 8 figs.

  12. Protection of AC and DC Microgrids

    DEFF Research Database (Denmark)

    Beheshtaein, Siavash; Savaghebi, Mehdi; Quintero, Juan Carlos Vasquez

    2015-01-01

    In future, distributed energy resources (RESs) will be utilized at consumption points. As a consequence, power flow and fault current would be bidirectional and topologydependent; and hence the conventional protection strategies would be inefficient. This paper categorizes the main challenges in AC...

  13. AC/RF Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [JLAB

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  14. Digital model for harmonic interactions in AC/DC/AC systems

    Energy Technology Data Exchange (ETDEWEB)

    Guarini, A.P.; Rangel, R.D.; Pilotto, L.A.S.; Pinto, R.J.; Passos Junior, R. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil)

    1994-12-31

    The main purpose of this paper is to present a model for calculation of HVdc converter harmonics taking into account the influence of the harmonic interactions between the ac systems in dc link transmissions. The ideas and methodologies used in the model development take into account the dc current ripple and ac voltage distortion in the ac systems. The theory of switching functions is applied to contemplate for the frequency conversions between the ac and dc sides, in an iterative process. It is possible then to obtain, even in balanced situations, non-characteristic harmonics that are produced by frequencies originated in the other terminal, which can be significant in a strongly coupled system, such as back-to-back configuration. (author) 9 refs., 3 figs.

  15. Safe-commutation principle for direct single-phase AC-AC converters for use in audio power amplification

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2004-01-01

    This paper presents an alternative safe commutation principle for a single phase bidirectional bridge, for use in the new generation of direct single-stage AC-AC audio power amplifiers. As compared with the bridge commutation with load current or source voltage sensing, in this approach...

  16. Safe-commutation principle for direct single-phase AC-AC converters for use in audio power amplification

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2004-01-01

    This paper presents an alternative safe commutation principle for a single phase bidirectional bridge, for use in the new generation of direct single-stage AC-AC audio power amplifiers. As compared with the bridge commutation with load current or source voltage sensing, in this approach...

  17. The Effective AC Response of Nonlinear Composites

    Institute of Scientific and Technical Information of China (English)

    WEI En-Bo; GU Guo-Qing

    2001-01-01

    A perturbative approach is used to study the AC response of nonlinear composite media, which obey a current-field relation of the form J = σ E + χ|E|2 E with components having nonlinear response at finite frequencies. For a sinusoidal applied field, we extend the local potential in terms of sinusoidal components at fundamental frequency and high-order harmonic frequencies to treat the nonlinear composites. For nonlinear composite media vith a low concentrations of spherical inclusions, we give the formulae of the nonlinear effective AC susceptibility χ*3ω at the third harmonic frequency.

  18. Ac response of a coupled double quantum dot

    Institute of Scientific and Technical Information of China (English)

    Xu Jie; W.Z. Shangguan; Zhan Shi-Chang

    2005-01-01

    The effect of phase-breaking process on the ac response of a coupled double quantum dot is studied in this paper based on the nonequilibrium Green function formalism. A general expression is derived for the ac current in the presence of electron-phonon interaction. The ac conductance is numerically computed and the results are compared with those in [Anatram M P and Datts S 1995 Phys. Rev. B 51 7632]. Our results reveal that the inter-dot electron tunnelling interplays with that between dots and electron reservoirs, and contributes prominently to the ac current when inter-dot tunnelling coupling is much larger than the tunnelling coupling between dots and electron reservoirs. In addition, the phase-breaking process is found to have a significant effect on the ac transport through the coupled double dot.

  19. Comparison of excitatory currents activated by different transmitters on crustacean muscle. II. Glutamate-activated currents and comparison with acetylcholine currents present on the same muscle.

    Science.gov (United States)

    Lingle, C; Auerbach, A

    1983-04-01

    The properties of glutamate-activated excitatory currents on the gm6 muscle from the foregut of the spiny lobsters Panulirus argus and interruptus and the crab Cancer borealis were examined using either noise analysis, analysis of synaptic current decays, or slow iontophoretic currents. The properties of acetylcholine currents activated in nonjunctional regions of the gm6 muscle were also examined. At 12 degrees C and -80 mV, the predominant time constant of power spectra from glutamate-activated current noise was approximately 7 ms and the elementary conductance was approximately 34 pS. At 12 degrees C and -80 mV, the predominant time constant of acetylcholine-activated channels was approximately 11 ms with a conductance of approximately 12 pS. Focally recorded glutamatergic extracellular synaptic currents on the gm6 muscle decayed with time constants of approximately 7-8 ms at 12 degrees C and -80 mV. The decay time constant was prolonged e-fold about every 225-mV hyperpolarization in membrane potential. The Q10 of the time constant of the synaptic current decay was approximately 2.6. The voltage dependence of the steady-state conductance increase activated by iontophoretic application of glutamate has the opposite direction of the steady-state conductance activated by cholinergic agonists when compared on the gm6 muscles. The glutamate-activated conductance increase is diminished with hyperpolarization. The properties of the marine crustacean glutamate channels are discussed in relation to glutamate channels in other organisms and to the acetylcholine channels found on the gm6 muscle and the gm1 muscle of the decapod foregut (Lingle and Auerbach, 1983).

  20. Pediatric keratoconus and iontophoretic corneal crosslinking: refractive and topographic evidence in patients underwent general and topical anesthesia, 18 months of follow-up.

    Science.gov (United States)

    Magli, Adriano; Chiariello Vecchio, Elisabetta; Carelli, Roberta; Piozzi, Elena; Di Landro, Felicia; Troisi, Salvatore

    2016-08-01

    To evaluate the efficiency and safety of iontophoretic transepithelial corneal crosslinking in pediatric patients with progressive keratoconus underwent general or topical anesthesia in 18 months follow-up. 13 patients (13 eyes) diagnosed with progressive keratoconus underwent corneal CXL with iontophoresis (I-CXL). Riboflavin solution was administered by iontophoresis for 5 min, and then UV-A irradiation (10 mW/cm) was performed for 9 min. Preoperative and post-operative visits at 1, 6, 12, and 18 months assessed the following parameters: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, corneal topography, optical tomography, and pachymetry with Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany), endothelial biomicroscopy (Konan Specular Microscope; Konan Medical, Inc., Hyogo, Japan). The paired Student t test was used to compare data during the follow-up. 10 males and 3 females with a mean age of 15.4 ± 1.7 years (range 11-18 years) were included. The results showed a stabilization of the refractive UCVA and BCVA as early as the first post-operative month, with a slight improvement over time. The Kmax remained stable throughout follow-up (p = 0.04). Transepithelial collagen crosslinking by iontophoresis, unlike other transepithelial techniques seems to halt pediatric keratoconus progression over 18 months. This is the second study evaluating CXL with iontophoresis in pediatric patients with progressive keratoconus with 18 months of follow-up using two different ways of anesthesia.

  1. Effect of Modulated Alternating and Direct Current Iontophoresis on Transdermal Delivery of Lidocaine Hydrochloride

    OpenAIRE

    Gaurav Bhatia; Banga, Ajay K.

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determi...

  2. Scaling of ac susceptibility and the nonlinear response function of high-temperature superconductors

    Institute of Scientific and Technical Information of China (English)

    CHEN; Kaixuan; NING; Zhenhua; XU; Hengyi; QI; Zhi; LU; Guo

    2005-01-01

    The amplitude-dependent ac susceptibility of high-temperature superconductors is shown to obey some empirical scaling relations. We try to analyze this behavior by extending a dc nonlinear response function of mixed state to the ac cases. The derived equations for critical current and ac susceptibility x(T) agree with the scaling relations of experimental data.

  3. Investigation and comparison of AC losses on stabilizer-free and copper stabilizer HTS tapes

    Science.gov (United States)

    Shen, Boyang; Li, Jing; Geng, Jianzhao; Fu, Lin; Zhang, Xiuchang; Li, Chao; Zhang, Heng; Dong, Qihuan; Ma, Jun; Coombs, T. A.

    2017-10-01

    This paper presents the measurement and simulation of Alternating Current (AC) losses on the Stabilizer-free and Copper Stabilizer High Temperature Superconducting (HTS) Tapes: SuperPower SF12100 and SCS12050. The AC loss measurement utilised electrical method to obtain overall losses with AC transport currents. The 2D H-formulation by COMSOL Multiphysics has been used to simulate the real geometry and multi-layer HTS tapes. Ferromagnetic AC losses of substrate have been assumed to be ignored as the substrates of SF12100 and SCS12050 are non-magnetic. Hysteresis AC losses in the superconducting layer, and eddy-current AC losses in copper stabilizer, silver overlayer and substrate were concerned in this investigation. The measured AC losses were compared to the AC losses from simulation, with 3 cases of different AC frequency 10, 100, and 1000 Hz. The eddy-current AC losses of copper stabilizer at frequency 1000 Hz were determined from both experiment and simulation. The estimation of AC losses with frequency at 10,000 Hz was also carried out using simulation method. Finally, the frequency dependence of AC losses from Stabilizer-free Tape and Copper Stabilizer Tape were compared and analysed.

  4. Analysis of Input and Output Ripples of PWM AC Choppers

    Directory of Open Access Journals (Sweden)

    Pekik Argo Dahono

    2008-11-01

    Full Text Available This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.

  5. 基于STC90C58的单相交流供电线路漏电流监测装置%STC90C58-based Device to Monitor Leakage Current of Single-phase AC Power Line

    Institute of Scientific and Technical Information of China (English)

    关旭俊; 谢力扬

    2014-01-01

    基于STC90C58设计了一种监测单相交流供电线路漏电流的装置。采用了微控制器和电能计量器件,可同时采集并显示单相交流供电线路相线电流、中性线电流和相线对地漏电流的幅值。可为判断漏电性质和排查漏电点提供数据支持,对提高漏电保安器的投入率、提高用电安全性、降低线损有一定的积极意义。%A device based on STC90C58 to monitor the leakage current of single-phase AC power line is designed .The device uses a micro-controller and a power energy IC ,it can simultaneously capture and display the amplitudes of the phase line current ,the neutral current and the phase-to-ground leakage current of the single-phase AC supply line .The device can determine the nature of leakage points and provide data to support the investigation ,it will have some positive significance to improve the input rate of leakage protectors and improve the security for using electricity and reduce line losses .

  6. High performance AC drives

    CERN Document Server

    Ahmad, Mukhtar

    2010-01-01

    This book presents a comprehensive view of high performance ac drives. It may be considered as both a text book for graduate students and as an up-to-date monograph. It may also be used by R & D professionals involved in the improvement of performance of drives in the industries. The book will also be beneficial to the researchers pursuing work on multiphase drives as well as sensorless and direct torque control of electric drives since up-to date references in these topics are provided. It will also provide few examples of modeling, analysis and control of electric drives using MATLAB/SIMULIN

  7. DC injection into low voltage AC networks

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    This report summarises the results of a study investigating the impact of levels of injected DC current injections on a low voltage AC distribution network systems in order to recommend acceptable limits of DC from microgeneration. Relevant literature is reviewed, and the impact of DC levels in distribution transformers, transformer modelling, and instrumental transformers are discussed. The impact of DC in residual current devices (RCD) and in domestic electricity watt hour meters is examined along with DC enhanced corrosion, corrosion failure, and the measurement of DC current injection. Sources of DC injection outlined include DC from computer power supplies, network faults, geomagnetic phenomena, lighting circuits/dimmers, and embedded generators.

  8. AC power generation from microbial fuel cells

    Science.gov (United States)

    Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

    2015-11-01

    Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

  9. A Study on Power Quality Improvement in PWM Controlled AC Voltage Controller

    Directory of Open Access Journals (Sweden)

    Ahmet ALTINTAŞ

    2009-04-01

    Full Text Available A lot of topologies of pulse-width modulated (PWM-AC controllers for single-phase and three-phase systems are proposed up to date. PWM-AC controllers have important advantages compared with the phase-controlled AC controllers using thyristors and triacs. The PWM-AC controller has sinusoidal current waveforms, smaller THD values, better power factor, faster dynamics, and smaller input/output filter. This article presents a novel control technique for application to PWM-AC controllers with ability of generating fewer harmonics. In the proposed control method, both the traditional AC voltage controllers and the PWM-AC controllers are combined; and smaller THD values are obtained. Thus, the harmonic pollution in the power system will be reduced; and consequently, the power quality will be increased. For this purpose, computer simulations are performed in order to investigate the proposed controller performance. The obtained results are compared with the conventional PWM-AC controller.

  10. Cooling Floor AC Systems

    Science.gov (United States)

    Jun, Lu; Hao, Ding; Hong, Zhang; Ce, Gao Dian

    The present HVAC equipments for the residential buildings in the Hot-summer-and-Cold-winter climate region are still at a high energy consuming level. So that the high efficiency HVAC system is an urgently need for achieving the preset government energy saving goal. With its advantage of highly sanitary, highly comfortable and uniform of temperature field, the hot-water resource floor radiation heating system has been widely accepted. This paper has put forward a new way in air-conditioning, which combines the fresh-air supply unit and such floor radiation system for the dehumidification and cooling in summer or heating in winter. By analyze its advantages and limitations, we found that this so called Cooling/ Heating Floor AC System can improve the IAQ of residential building while keep high efficiency quality. We also recommend a methodology for the HVAC system designing, which will ensure the reduction of energy cost of users.

  11. AC electrophoretic deposition of organic-inorganic composite coatings.

    Science.gov (United States)

    Yoshioka, T; Chávez-Valdez, A; Roether, J A; Schubert, D W; Boccaccini, A R

    2013-02-15

    Alternating current electrophoretic deposition (AC-EPD) of polyacrylic acid (PAA)-titanium oxide (TiO(2)) nanoparticle composites on stainless steel electrodes was investigated in basic aqueous solution. AC square wave with duty cycle of 80% was applied at a frequency of 1 kHz. FTIR-ATR spectra showed that both AC and direct current (DC) EPD successfully deposited PAA-TiO(2) composites. The deposition rate using AC-EPD was lower than that obtained in direct current DC-EPD. However, the microstructure and surface morphology of the deposited composite coatings were different depending on the type of electric field applied. AC-EPD applied for not more than 5 min led to smooth films without bubble formation, while DC-EPD for 1 min or more showed deposits with microstructural defects possibly as result of water electrolysis. AC-EPD was thus for the first time demonstrated to be a suitable technique to deposit organic-inorganic composite coatings from aqueous suspensions, showing that applying a square wave and frequency of 1 kHz leads to uniform PAA-TiO(2) composite coatings on conductive materials.

  12. POWER FACTOR IMPROVEMENT IN THREE PHASE AC-AC CONVERTER THROUGH MODIFIED SPWM

    Directory of Open Access Journals (Sweden)

    P.VASUKI,

    2011-02-01

    Full Text Available Recently, a new generation of ac-ac single-phase and three-phase power converters with more commutations per half cycle has been proposed for ac power due to the increasing availability and power capability of high frequency controlled-on and off power emiconductor switching devices. This paper presents three phase ac-acconverter whose control strategy is based on modified sinusoidal ulse-width modulation switching technique. As majority of the industrial loads are being inductive, the power factor is less. To improve the power factor, the delayed current is shifted to the input voltage, through a modification of the classical sinusoidal pulse width modulation switching technique. In this way, the decrease in the phase angle between the input current and voltage is feasible, and consequently, high cost compensation capacitors can be avoided. The improvement of power factor through this switching technique on the proposed converter is investigated and verified via simulation using the software Matlab/Simulink.

  13. Harmonic-free line-commutated ac/dc rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    Villablanca, Miguel E. [Electrical Engineering Department, University of Santiago, P.O. Box 10233, Santiago (Chile)

    2009-11-15

    In this paper both a method and apparatus are applied to different configurations of line-commutated ac/dc rectifiers to reduce the distortion of currents flowing from the ac supply. The load may be either inductive or capacitive. The technology involves an accurate shaping of the dc current by using two self-commutated switches. This dc-current shaping is reflected back into the shaping of the ac input currents, which become pure sine waves. Thyristor-based rectifying operation is possible with a simple control circuit, which is able to deal with both rapid load variations and failures in the self-commutated switches. Furthermore, the overlap conduction of bridge thyristors is eliminated completely. Experimental verification is provided from a 400-V 30-kVA 50-Hz laboratory prototype. (author)

  14. Software Development for ALMA in Chile: The ACS-UTFSM Group.

    Science.gov (United States)

    von Brand, H. H.

    ALMA Common Software (ACS) provides a common software framework for ALMA, the Atacama Large Millimeter Array in Chile. ACS is a collection of well-documented patterns for controlling systems and a set of components written to those patterns. In its core, ACS is a distributed, object-oriented system, written on top of CORBA. The ACS-UTFSM Group started as some students of informatics did summer jobs at the La Silla Observatory of ESO, where they became acquainted with ACS. Their interest led them to continue working on ACS on their own, and they eventually became official developers of the package. Now the group is being funded by project ALMA-CONICYT 31060008 ``Software Development for ALMA: Building Up Expertise to Meet ALMA Software Requirements within a Chilean University''. Several members of the original group are now working for ALMA, which fullfills one of the goals of the project. Some parts of ACS developed by the ACS-UTFSM Group include H3E (Hardware End-to-End Example), a Lego model of a telescope and its controlling software for training and demonstration purposes; and CDBChecker, a tool to verify the consistency of the configuration database for a ACS deployment. Currently we are working towards a general framework for telescope control using ACS, in order to simplify the deployment of new instruments; and repackaging ACS so it is easier to install and use. A master's thesis is exploring the real-time requirements of ACS.

  15. Measurement of AC loss of superconductors by vaporizing method

    Energy Technology Data Exchange (ETDEWEB)

    Wakabayashi, Hiroshi; Isono, Takaaki; Matsui, Kunihiro; Fujisaki, Reishi; Nunoya, Yoshihiko; Koizumi, Norikiyo; Takahashi, Yoshikazu; Tsuji, Hiroshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    1995-07-01

    In Japan Atomic Energy Research Institute, the development of superconducting pulse conductors for next period nuclear fusion reactors has been carried out. For these conductors, the rated current of 46 kA and the rated magnetic field of 13T are demanded. When the pulse excitation of superconductors is carried out, AC loss arises, and the temperature of the superconductors rises, and when it exceeds a certain value, the superconducting state cannot be maintained. Therefore, the AC loss of pulse conductors must be limited to a low value. It is difficult to evaluate the AC loss of superconductors by calculation, therefore, it is evaluated by actual measurement. There are magnetizing method and vaporizing method for measuring the AC loss. This time, the equipment for measuring the AC loss of 40 kA class superconductors by vaporizing method which measures the helium gas quantity vaporizing at the time of AC loss occurrence was designed and manufactured for the first time. The method of measuring the AC loss, the structure of the measuring equipment, the helium gas recovering part and the measuring part, the countermeasures for preventing helium gas leakage, the resistance heater for calibration, and the results of measurement are reported. (K.I.)

  16. ACS CCD Stability Monitor

    Science.gov (United States)

    Grogin, Norman

    2012-10-01

    A moderately crowded stellar field in the cluster 47 Tuc {6 arcmin West of the cluster core} is observed every four months with the WFC. The first visit exercises the full suite of broad and narrow band imaging filters and sub-array modes; following visits observe with only the six most popular Cycle 18 filters in full-frame mode. The positions and magnitudes of objects will be used to monitor local and large scale variations in the plate scale and the sensitivity of the detectors and to derive an independent measure of the detector CTE. One exposure in each sub-array mode with the WFC will allow us to verify that photometry obtained in full-frame and in sub-array modes are repeatable to better than 1%. This test is important for the ACS Photometric Cross-Calibration program, which uses sub-array exposures. This program may receive additional orbits to investigate ORIENT-dependent geometric distortion, which motivates the ORIENT and BETWEEN requirement on the first visit.

  17. AcEST: DK956383 [AcEST

    Lifescience Database Archive (English)

    Full Text Available TAC +HPGP Sbjct: 130 TP----GQAEEEKIEPLAPPVQKAVIDINQPQVCKNKGCGQTFKERDNHETACSHHPGPA 185 Query: 574 VF 579 VF S...AC +HPGP Sbjct: 130 TP----GQAEEEKIEPLAPPVQKAVIDINQPQVCKNKGCGQTFKERDNHETACSHHPGPA 185 Query: 574 VF 579 VF Sb

  18. Measurement of AC losses in a racetrack superconducting coil made from YBCO coated conductor

    DEFF Research Database (Denmark)

    Seiler, Eugen; Abrahamsen, Asger Bech; Kovac, Jan

    2012-01-01

    to reinforce it. The AC loss is measured versus the transport current Ia with the coil immersed in liquid nitrogen. Measurements at frequencies 21 Hz, 36 Hz and 72 Hz are compared. The AC losses follow I2 a dependence at low current amplitudes and I3 a at high amplitudes. After cutting the inner steel frame...

  19. Using AC Motors in Robotics

    Directory of Open Access Journals (Sweden)

    Hosein Marzi

    2008-11-01

    Full Text Available It has been proven that fuzzy controllers are capable of controlling non-linear systems where it is cumbersome to develop conventional controllers based on mathematical modeling. This paper describes designing fuzzy controllers for an AC motor run mechanism. It also compares performance of two controllers designed based on Mamdani and Takagi-Sugeno with the conventional control scheme in a short track length, following a high disturbance. Fine and rapid control of AC motors have been a challenge and the main obstacle in gaining popularity in use of AC motors in robots actuators. This chapter reviews how use of intelligent control scheme can help to solve this problem.

  20. Fabrication of alumina films with laminated structures by ac anodization

    Directory of Open Access Journals (Sweden)

    Hiroyo Segawa

    2014-01-01

    Full Text Available Anodization techniques by alternating current (ac are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50–200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  1. MATHEMATICAL MODELING OF AC ELECTRIC POINT MOTOR

    Directory of Open Access Journals (Sweden)

    S. YU. Buryak

    2014-03-01

    Full Text Available Purpose. In order to ensure reliability, security, and the most important the continuity of the transportation process, it is necessary to develop, implement, and then improve the automated methods of diagnostic mechanisms, devices and rail transport systems. Only systems that operate in real time mode and transmit data on the instantaneous state of the control objects can timely detect any faults and thus provide additional time for their correction by railway employees. Turnouts are one of the most important and responsible components, and therefore require the development and implementation of such diagnostics system.Methodology. Achieving the goal of monitoring and control of railway automation objects in real time is possible only with the use of an automated process of the objects state diagnosing. For this we need to know the diagnostic features of a control object, which determine its state at any given time. The most rational way of remote diagnostics is the shape and current spectrum analysis that flows in the power circuits of railway automatics. Turnouts include electric motors, which are powered by electric circuits, and the shape of the current curve depends on both the condition of the electric motor, and the conditions of the turnout maintenance. Findings. For the research and analysis of AC electric point motor it was developed its mathematical model. The calculation of parameters and interdependencies between the main factors affecting the operation of the asynchronous machine was conducted. The results of the model operation in the form of time dependences of the waveform curves of current on the load on engine shaft were obtained. Originality. During simulation the model of AC electric point motor, which satisfies the conditions of adequacy was built. Practical value. On the basis of the constructed model we can study the AC motor in various mode of operation, record and analyze current curve, as a response to various changes

  2. Phosphor-in-glass for high-powered remote-type white AC-LED.

    Science.gov (United States)

    Lin, Hang; Wang, Bo; Xu, Ju; Zhang, Rui; Chen, Hui; Yu, Yunlong; Wang, Yuansheng

    2014-12-10

    The high-powered alternating current (AC) light-emitting diode (LED) (AC-LED), featuring low cost, high energy utilization efficiency, and long service life, will become a new economic growth point in the field of semiconductor lighting. However, flicker of AC-LED in the AC cycles is not healthy for human eyes, and therefore need to be restrained. Herein we report an innovation of persistent "phosphor-in-glass" (PiG) for the remote-type AC-LED, whose afterglow can be efficiently activated by the blue light. It is experimentally demonstrated that the afterglow decay of PiG in the microsecond range can partly compensate the AC time gap. Moreover, the substitution of inorganic glass for organic resins or silicones as the encapsulants would bring out several technological benefits to AC-LED, such as good heat-dissipation, low glare, and excellent physical/chemical stability.

  3. 75 FR 13646 - Public Meeting With Interested Persons To Discuss the Proposed AC 20-42D, Hand Fire Extinguishers...

    Science.gov (United States)

    2010-03-22

    ... Federal Aviation Administration Public Meeting With Interested Persons To Discuss the Proposed AC 20-42D... received regarding proposed advisory circular (AC) 20-42D, Hand Fire Extinguishers for use in Aircraft... (IASFPWG) to draft a revision to the current AC 20-42C, issued on March 1984, by incorporating...

  4. Aislamiento acústico

    Directory of Open Access Journals (Sweden)

    Tobío, J. M.

    1970-07-01

    Full Text Available This is a very specific subject in the field of architectural acoustics, namely, insulation'. Emphasis is placed on the theoretical foundations of this phenomenon, and the most simple formula are developed to calculate easily the transmission losses of a material or the constructional insulating arrangements. The practical aspect of insulation can be considered by means of several graphs and charts, without the use of mathematics, and utilising common materials, that will not substantially increase the cost of the project. Finally this papers offers a critical discussion of building codes, and their reference to the acoustical insulation of dwellings, and data is included on the new regulations of the Madrid Municipality.Se trata un tema muy concreto de la Acústica Arquitectónica, el aislamiento, haciendo hincapié en los fundamentos teóricos del fenómeno y estableciendo las fórmulas más sencillas que permiten calcular fácilmente las pérdidas de transmisión de un material o disposición constructiva aislante. Varias gráficas y abacos permiten abordar, sin ningún tratamiento matemático, el problema práctico del aislamiento, aprovechando los materiales comunes y sin ocasionar gastos que graven sustancialmente el importe del proyecto. Por último, se hace un estudio crítico de las normas y su incidencia en los problemas del aislamiento de viviendas, incluyendo datos referentes a la nueva Ordenanza del Ayuntamiento de Madrid.

  5. Partial AC-coupling minigrids

    Energy Technology Data Exchange (ETDEWEB)

    Moix, Pierre-Olivier; Ruchet, Claude [Studer Innotec, Sion (Switzerland)

    2010-07-01

    Partial AC-coupling: - It is feasible to make AC-coupling of some compatible elements without V/f droops. Standard elements available on the market were tested. - Optimum design for efficiency is a share of the solar modules between DC-coupling with a solar charger and AC-coupling with a grid inverter according to the load profile. - Partial AC-coupling is better in term of robustness; it is more reliable to have at least a part of the solar production connected directly to DC, or even only DC coupling. The presented concepts are not only theoretical but were implemented and tested on real products available on the market. Many tests have been done to find out the limits and problems that can occur with the use of grid connected and stand alone inverter together. Many combinations were tested and it was found robust enough to be used in the field with the precautions mentioned about microcycling. (orig.)

  6. AC plasma anemometer—characteristics and design

    Science.gov (United States)

    Marshall, Curtis; Matlis, Eric; Corke, Thomas; Gogineni, Sivaram

    2015-08-01

    The characteristics and design of a high-bandwidth flow sensor that uses an AC glow discharge (plasma) as the sensing element is presented. The plasma forms in the air gap between two protruding low profile electrodes attached to a probe body. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean and fluctuating velocity components. The anemometer circuitry includes resistance and capacitance elements that simulate a dielectric-barrier to maintain a diffuse plasma, and a constant-current feedback control that maintains operation within the desired glow discharge regime over an extended range of air velocities. Mean velocity calibrations are demonstrated over a range from 0 to 140 m s-1. Over this velocity range, the mean output voltage varied linearly with air velocity, providing a constant static sensitivity. The effect of the electrode gap and input AC carrier frequency on the anemometer static sensitivity and dynamic response are investigated. Experiments are performed to compare measurements obtained with a plasma sensor operating at two AC carrier frequencies against that of a constant-temperature hot-wire. All three sensors were calibrated against the same known velocity reference. An uncertainty based on the standard deviation of the velocity calibration fit was applied to the mean and fluctuating velocity measurements of the three sensors. The motivation is not to replace hot-wires as a general measurement tool, but rather as an alternative to hot-wires in harsh environments or at high Mach numbers where they either have difficulty in surviving or lack the necessary frequency response.

  7. Distributed AC power flow method for AC and AC-DC hybrid ...

    African Journals Online (AJOL)

    DR OKE

    Present MGs incorporate AC and DC sources and loads along with storage and power ... Keywords: Microgrid (MG), Distributed Energy Resources (DER), Particle ... But in case of renewable based MGs, where small and intermittent sources ...

  8. System and method for determining stator winding resistance in an AC motor

    Science.gov (United States)

    Lu, Bin; Habetler, Thomas G.; Zhang, Pinjia; Theisen, Peter J.

    2011-05-31

    A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.

  9. AC and Phase Sensing of Nanowires for Biosensing.

    Science.gov (United States)

    Crescentini, Marco; Rossi, Michele; Ashburn, Peter; Lombardini, Marta; Sangiorgi, Enrico; Morgan, Hywel; Tartagni, Marco

    2016-04-19

    Silicon nanowires are label-free sensors that allow real-time measurements. They are economical and pave the road for point-of-care applications but require complex readout and skilled personnel. We propose a new model and technique for sensing nanowire sensors using alternating currents (AC) to capture both magnitude and phase information from the sensor. This approach combines the advantages of complex impedance spectroscopy with the noise reduction performances of lock-in techniques. Experimental results show how modifications of the sensors with different surface chemistries lead to the same direct-current (DC) response but can be discerned using the AC approach.

  10. 一种新颖的抑制两级式直交逆变器输入电流低频脉动的方法%A Novel Technique for Low Frequency Input Current Ripple Reduction In Two-stage DC-AC Inverter

    Institute of Scientific and Technical Information of China (English)

    邓翔; 韦徵; 龚春英; 王建华; 张方华

    2011-01-01

    两级式直交单相逆变器输入电流中含有两倍于逆变器输出频率的低频分量,这些低频分量幅值相对其平均值的比例很高,可达到30%以上,严重时将会影响直流电源系统的稳定性,也会大大影响输入电压源的蓄电池、燃料电池的使用寿命。通过研究该电流低频分量产生的原因,对前级直直变换器提出一种新的控制策略,即在传统的控制策略中引入谐振控制器,可以有效的抑制直直变换器输出滤波电感电流的低频脉动,进而可以有效抑制变换器低压侧输入电源电流低频脉动分量。给出谐振控制器的设计方法,以及引入谐振控制器之后系统各环路的传递函数,分析满足系统稳定性要求的设计准则。最后通过仿真和实验验证该控制策略对于抑制两级式直交逆变器输入电流低频脉动的有效性。%The input current of the two-stage DC-AC inverter contains low frequency ripple which is twice the inverter's output frequency.The proportion of the low frequency current ripple's amplitude to the average current is very high and it could be achieved more than 30%.The stability of DC power system and the longevity of the input voltage source such as battery or fuel cell could be influenced seriously.The new control strategy for the previous stage DC/DC converter was proposed by analyzing the reason of the low frequency current ripple production in this paper.The resonant controller is introduced in the traditional control strategy.The proposed new control strategy will be very useful to reduce the current ripple of output filter inductor in the DC/DC converter,and the input current ripple of the two-stage DC-AC inverter will also be lower.The design of the resonant controller and the transfer function of the system were given in the paper,and the design principles of system stability were also analyzed.At last,the effectiveness of proposed new control strategy to reduce the input

  11. AC losses in circular arrangements of parallel superconducting tapes

    DEFF Research Database (Denmark)

    Kühle (fratrådt), Anders Van Der Aa; Træholt, Chresten; Däumling, Manfred

    1998-01-01

    The DC and AC properties of superconducting tapes connected in parellel and arranged in a single closed layer on two tubes (correspondig to power cable models with infinite pitch) with different diameters are compared. We find that the DC properties, i.e. the critical currents of the two arrangem......The DC and AC properties of superconducting tapes connected in parellel and arranged in a single closed layer on two tubes (correspondig to power cable models with infinite pitch) with different diameters are compared. We find that the DC properties, i.e. the critical currents of the two...... arrangements, scale with the number of tapes and hence appear to be independent of the diameter.However, the AC loss per tape (for a given current per tape) appears to decrease with increasing diameter of the circular arrangement. Compared to a model for the AC loss in a continuous superconducting layer...... (Monoblock model) the measured values are about half an order of magnitude higher than expected for the small diameter arrangement. When compared to the AC loss calculated for N individual superconducting tapes using a well known model ( Norris elliptical) the difference is slightly smaller....

  12. Diagnostics of the Fermilab Tevatron using an AC dipole

    Energy Technology Data Exchange (ETDEWEB)

    Miyamoto, Ryoichi [Univ. of Texas, Austin, TX (United States)

    2008-08-01

    The Fermilab Tevatron is currently the world's highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron's beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f ~ 20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of the beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of non-linear perturbations from sextupole and octupole elements.

  13. A Novel High Performance Bridgeless Ac-Dc Boost Converter

    Directory of Open Access Journals (Sweden)

    S.M.AshrafulAlam Mohon

    2016-08-01

    Full Text Available A new single phase high performance bridgeless AC-DC Boost converter is proposed. The converter is made bridgeless by the use of two unidirectional switches and two diodes at the input ac side for power conversion for both positive and negative half cycle. Because of the high frequency switching, the power factor of the circuit is inherently corrected and it requires a small filter to make the input current near sinusoidal with limited THD. The significant improvement in THD makes the circuit a good choice in applications needing AC-DC conversion with power conditioning. The circuit exhibits such better performances than conventional AC-DC boost converter with variable loads at constant frequency switching with no additional control circuits. The efficiency of the circuit is also satisfactory. Analysis and simulation results of the circuit are obtained by using software simulation. The main advantage of this new AC-DC converter is its superior power quality over conventional AC-DC boost converter

  14. Superconducting shielded core reactor with reduced AC losses

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Yung S.; Hull, John R.

    2006-04-04

    A superconducting shielded core reactor (SSCR) operates as a passive device for limiting excessive AC current in a circuit operating at a high power level under a fault condition such as shorting. The SSCR includes a ferromagnetic core which may be either closed or open (with an air gap) and extends into and through a superconducting tube or superconducting rings arranged in a stacked array. First and second series connected copper coils each disposed about a portion of the iron core are connected to the circuit to be protected and are respectively wound inside and outside of the superconducting tube or rings. A large impedance is inserted into the circuit by the core when the shielding capability of the superconducting arrangement is exceeded by the applied magnetic field generated by the two coils under a fault condition to limit the AC current in the circuit. The proposed SSCR also affords reduced AC loss compared to conventional SSCRs under continuous normal operation.

  15. Hopping models and ac universality

    DEFF Research Database (Denmark)

    Dyre, Jeppe; Schrøder, Thomas

    2002-01-01

    Some general relations for hopping models are established. We proceed to discuss the universality of the ac conductivity which arises in the extreme disorder limit of the random barrier model. It is shown that the relevant dimension entering into the diffusion cluster approximation (DCA) is the h......) is the harmonic (fracton) dimension of the diffusion cluster. The temperature scaling of the dimensionless frequency entering into the DCA is discussed. Finally, some open problems regarding ac universality are listed.......Some general relations for hopping models are established. We proceed to discuss the universality of the ac conductivity which arises in the extreme disorder limit of the random barrier model. It is shown that the relevant dimension entering into the diffusion cluster approximation (DCA...

  16. Wind-powered asynchronous AC/DC/AC converter system. [for electric power supply regulation

    Science.gov (United States)

    Reitan, D. K.

    1973-01-01

    Two asynchronous ac/dc/ac systems are modelled that utilize wind power to drive a variable or constant hertz alternator. The first system employs a high power 60-hertz inverter tie to the large backup supply of the power company to either supplement them from wind energy, storage, or from a combination of both at a preset desired current; rectifier and inverter are identical and operate in either mode depending on the silicon control rectifier firing angle. The second system employs the same rectification but from a 60-hertz alternator arrangement; it provides mainly dc output, some sinusoidal 60-hertz from the wind bus and some high harmonic content 60-hertz from an 800-watt inverter.

  17. Three-Level AC-DC-AC Z-Source Converter Using Reduced Passive Component Count

    DEFF Research Database (Denmark)

    Loh, Poh Chiang; Gao, Feng; Tan, Pee-Chin;

    2007-01-01

    This paper presents a three-level ac-dc-ac Z-source converter with output voltage buck-boost capability. The converter is implemented by connecting a low cost front-end diode rectifier to a neutral-point-clamped inverter through a single X-shaped LC impedance network. The inverter is controlled...... to switch with a three-level output voltage, where the middle neutral potential is uniquely tapped from the star-point of a wye-connected capacitive filter placed before the front-end diode rectifier for input current filtering. Through careful control, the resulting converter can accurately produce...... the correct volt-sec average at its output, while simultaneously achieving inductive voltage boosting. More interestingly, these performance features are achieved with no increase in the number of semiconductor commutations, and hence no increase in switching losses. The proposed converter therefore offers...

  18. Speed Control of DC Motor using AC/AC/DC Converter Based on Intelligent Techniques

    Directory of Open Access Journals (Sweden)

    Rakan Kh Antar

    2013-05-01

    Full Text Available    This paper describes the application of ac/ac/dc and ac/dc converters to control the speed of a separately excited DC motor. Artificial neural network and PI controller are trained to select the desired values of firing angles for triggering thyristors of the ac/ac/dc and ac/dc bridge converters in order to control the speed of the dc motor at a desired value with constant and different load torques in order to obtain the best speed response. Simulation results show that the rising time for ac/dc and ac/ac/dc converters at 250rpm are reduced about 79% and 89% respectively, while delay time it reduced about 69% and 64% respectively. Therefore, speed response of the dc motor is more efficient for closed loop system compared with open loop also the response of ac/ac/dc converter is better than ac/dc converter.

  19. AC410 Unit 9 Assignment

    OpenAIRE

    Laynebaril1

    2017-01-01

     AC410 Unit 9 Assignment Click Link Below To Buy: http://hwcampus.com/shop/ac410-unit-9-assignment/   18–29. The CPA firm of Carson & Boggs LLP is performing an internal control audit in accordance with PCAOB Standard No. 5. The partner in charge of the engagement has asked you to explain the process of determining which controls to test. Describe the process, presenting each of the links in this process and a short summary of how the auditors approach each of them. v ...

  20. Electrothermal ac electro-osmosis

    Science.gov (United States)

    Gagnon, Zachary R.; Chang, Hsueh-Chia

    2009-01-01

    Two ac polarization mechanisms, charge accumulation due to electrode double layer charging and bulk permittivity/conductivity gradients generated by Joule heating, are combined in the double layer by introducing zwitterions to produce a new ac electrokinetic pump with the largest velocity (>1 mm/s) and flow penetration depth (100 μm) reported for low-conductivity fluids. The large fluid velocity is due to a quartic scaling with respect to voltage, as is true of electrothermal flow, but exhibits a clear maximum at a frequency corresponding to the electrode double layer inverse RC time.

  1. Nuclear structure of $^{231}$Ac

    CERN Document Server

    Boutami, R; Mach, H; Kurcewicz, W; Fraile, L M; Gulda, K; Aas, A J; García-Raffi, L M; Løvhøiden, G; Martínez, T; Rubio, B; Taín, J L; Tengblad, O

    2008-01-01

    The low-energy structure of 231Ac has been investigated by means of gamma ray spectroscopy following the beta-decay of 231Ra. Multipolarities of 28 transitions have been established by measuring conversion electrons with a mini-orange electron spectrometer. The decay scheme of 231Ra --> 231Ac has been constructed for the first time. The Advanced Time Delayed beta-gamma-gamma(t) method has been used to measure the half-lives of five levels. The moderately fast B(E1) transition rates derived suggest that the octupole effects, albeit weak, are still present in this exotic nucleus.

  2. AcEST: DK963222 [AcEST

    Lifescience Database Archive (English)

    Full Text Available sp|P81919|OR46A_DROME Odorant receptor 46a, isoform A OS=Drosoph... 32 2.8 sp|Q5MJ68|SPDYC_HUMAN Speed...FCFKA 181 CS +T + AV S L + +YV + AC Q FI C+ A Sbjct: 262 CSVLVLTANFYAIAVLSDERLELFKYVTYQACMLIQIFILCYYA 305 >sp|Q5MJ68|SPDYC_HUMAN Spee

  3. AcEST: DK953266 [AcEST

    Lifescience Database Archive (English)

    Full Text Available 34 0.49 sp|A5VSF3|ACSA_BRUO2 Acetyl-coenzyme A synthetase OS=Brucella ov... 34 0.49 sp|Q8YJ48|ACSA_BRUME Ac... K++ + NK L+ R G WG GR++ Sbjct: 180 FVITADEGVRGGKPVALKENTDTAIDIAAKQYVMVNKVLVVRRTGGKVSWGRGRDL 235 >sp|A5VSF3|ACSA_BRUO2

  4. AcEST: BP918420 [AcEST

    Lifescience Database Archive (English)

    Full Text Available D 180 >sp|A8AC98|APGM_IGNH4 2,3-bisphosphoglycerate-independent phosphoglycerate mutase OS=Ignicoccus hosp...italis (strain KIN4/I / DSM 18386 / JCM 14125) GN=apgM PE=3 SV=1 Length = 416 Score

  5. AcEST: BP921446 [AcEST

    Lifescience Database Archive (English)

    Full Text Available 34 2e-30 tr|A4VIU1|A4VIU1_PSEU5 Putative uncharacterized protein OS=Pseud... 129 1e-28 tr|Q11HF6|Q11HF6_MESSB...EHTHLMLDSKAGWVEPHIQAGDRCFAEYPDESLAQWHERLGL 159 >tr|Q11HF6|Q11HF6_MESSB Glutathione-dependent formaldehyde-ac

  6. AcEST: BP917259 [AcEST

    Lifescience Database Archive (English)

    Full Text Available Q96AC6|KIFC2_HUMAN Kinesin-like protein KIFC2 OS=Homo sapiens... 30 9.0 sp|O88737|BSN_MOUSE Protein bassoon ... WGQPG AAGS + PG Sbjct: 748 SSSPTEWVKWSWGQPG-------AAGSRAPPG 772 >sp|O88737|BSN_MOUSE Protein bassoon

  7. AcEST: DK947455 [AcEST

    Lifescience Database Archive (English)

    Full Text Available tative uncharacterized protein OS=Picea... 246 9e-64 tr|A8QIH7|A8QIH7_MORAL Chlor...DPTARSDNGSCEYEFKE 479 >tr|A8QIH7|A8QIH7_MORAL Chloroplast ribulose-1,5-bisphosphate carboxylase/oxygenase ac

  8. AcEST: DK943932 [AcEST

    Lifescience Database Archive (English)

    Full Text Available rella paten... 145 2e-33 tr|B6T2L2|B6T2L2_MAIZE Sedoheptulose-1,7-bisphosphatase ...EAL++SHVCK+AC Sbjct: 67 ATACVNTFGDEQLAVDMLADKLLFEALRHSHVCKYAC 103 >tr|B6T2L2|B6T2L2_MAIZE Sedoheptulose-1,7-

  9. AcEST: DK961189 [AcEST

    Lifescience Database Archive (English)

    Full Text Available OS=A... 127 7e-29 sp|Q94B08|GCP1_ARATH Germination-specific cysteine protease 1 OS... 125 2e-28 sp|P00785|AC...IRNSWGLNWGDSGYVKLQRNIDDPFGKCGIAMMPSYP 347 >sp|Q94B08|GCP1_ARATH Germination-specific cysteine protease 1 OS=

  10. Application of the reciprocity theorem to EEG inversion and optimization of EEG-driven transcranial current stimulation (tCS, including tDCS, tACS, tRNS)

    CERN Document Server

    Ruffini, Giulio

    2015-01-01

    Multichannel transcranial current stimulation (tCS) systems offer the possibility of EEG-guided optimized, non-invasive brain stimulation. In this brief technical note I explain how it is possible to use tCS electric field realistic brain model to create a forward "lead-field" matrix and, from that, an EEG inverter for cortical mapping. Starting from EEG I show how to generate 2D cortical surface dipole fields that could produce the observed EEG electrode voltages. The main tool is the reciprocity theorem derived by Helmholtz. The application of reciprocity for the generation of a forward mapping matrix (lead field matrix as is sometimes known) is well known [Rush and Driscoll, 1969], but here we will use it in combination with the realistic head models of [Miranda et al 2013] to provide cortical mapping solutions compatible with realistic head model tCS optimization. I also provide a generalization of the reciprocity theorem [Helmholtz 1853] to the case of multiple electrode contact points and dipole sources...

  11. Single phase AC-DC power factor corrected converter with high frequency isolation using buck converter

    Directory of Open Access Journals (Sweden)

    R. Ramesh,

    2014-03-01

    Full Text Available Single phase ac-dc converters having high frequency isolation are implemented in buck, boost, buck-boost configuration with improving the power quality in terms of reducing the harmonics of input current. The paperpropose the circuit configuration, control mechanism, and simulation result for the single phase ac-dc converter.

  12. harmonics: generation and suppression in ac system networks

    African Journals Online (AJOL)

    2012-11-03

    Nov 3, 2012 ... HARMONICS: GENERATION AND SUPPRESSION IN AC. SYSTEM NETWORKS .... If Vs = 295V; Z = (8 + j6)Ω and δ = 2π/3, the output voltage, Vo and ... tor current assume the characteristics shown in figure. 8. The output ...

  13. Calculation of AC losses in large HTS stacks and coils

    DEFF Research Database (Denmark)

    Zermeno, Victor; Abrahamsen, Asger Bech; Mijatovic, Nenad;

    2012-01-01

    In this work, we present a homogenization method to model a stack of HTS tapes under AC applied transport current or magnetic field. The idea is to find an anisotropic bulk equivalent for the stack of tapes, where the internal alternating structures of insulating, metallic, superconducting and su...

  14. Novel dielectric reduces corona breakdown in ac capacitors

    Science.gov (United States)

    Loehner, J. L.

    1972-01-01

    Dielectric system was developed which consists of two layers of 25-gage paper separated by one layer of 50-gage polypropylene to reduce corona breakdown in ac capacitors. System can be used in any alternating current application where constant voltage does not exceed 400 V rms. With a little research it could probably be increased to 700 to 800 V rms.

  15. Recommended ACS Syllabus for Introductory Courses in Polymer Chemistry.

    Science.gov (United States)

    Seymour, Raymond B.

    1982-01-01

    Provides syllabus for courses in introductory polymer chemistry (including major topics and recommended time allotments) and currently available textbooks and audio courses which may be used with the syllabus. Syllabus topics are congruent with those used in American Chemical Society (ACS) standardized examination in polymer chemistry. (Author/JN)

  16. ACS from development to operations

    Science.gov (United States)

    Caproni, Alessandro; Colomer, Pau; Jeram, Bogdan; Sommer, Heiko; Chiozzi, Gianluca; Mañas, Miguel M.

    2016-08-01

    The ALMA Common Software (ACS), provides the infrastructure of the distributed software system of ALMA and other projects. ACS, built on top of CORBA and Data Distribution Service (DDS) middleware, is based on a Component- Container paradigm and hides the complexity of the middleware allowing the developer to focus on domain specific issues. The transition of the ALMA observatory from construction to operations brings with it that ACS effort focuses primarily on scalability, stability and robustness rather than on new features. The transition came together with a shorter release cycle and a more extensive testing. For scalability, the most problematic area has been the CORBA notification service, used to implement the publisher subscriber pattern because of the asynchronous nature of the paradigm: a lot of effort has been spent to improve its stability and recovery from run time errors. The original bulk data mechanism, implemented using the CORBA Audio/Video Streaming Service, showed its limitations and has been replaced with a more performant and scalable DDS implementation. Operational needs showed soon the difference between releases cycles for Online software (i.e. used during observations) and Offline software, which requires much more frequent releases. This paper attempts to describe the impact the transition from construction to operations had on ACS, the solution adopted so far and a look into future evolution.

  17. Segmented superconducting tape having reduced AC losses and method of making

    Science.gov (United States)

    Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Holesinger, Terry G.; Wang, Haiyan

    2009-09-22

    A superconducting tape having reduced AC losses. The tape has a high temperature superconductor layer that is segmented. Disruptive strips, formed in one of the tape substrate, a buffer layer, and the superconducting layer create parallel discontinuities in the superconducting layer that separate the current-carrying elements of the superconducting layer into strips or filament-like structures. Segmentation of the current-carrying elements has the effect of reducing AC current losses. Methods of making such a superconducting tape and reducing AC losses in such tapes are also disclosed.

  18. Analytical approximation for AC losses in thin power-law superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sokolovsky, V; Meerovich, V [Physics Department, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva, 84105 (Israel)

    2007-08-15

    AC losses in the superconducting parts of tapes and multifilamentary coated conductors that are subjected to AC magnetic fields are an important component of the total losses in such composites. The analytical expression for AC losses in a thin superconducting strip with a power-law voltage-current characteristic and critical current depending on a magnetic field is obtained for the case of asymptotically high perpendicular magnetic fields. The losses caused by closure currents are estimated. The results show that the Bean model gives significantly understated values for coated conductors. The applicability of the obtained expressions is analyzed.

  19. Stability analysis of direct current control in current source rectifier

    DEFF Research Database (Denmark)

    Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Current source rectifier with high switching frequency has a great potential for improving the power efficiency and power density in ac-dc power conversion. This paper analyzes the stability of direct current control based on the time delay effect. Small signal model including dynamic behaviors...... of dc link is developed to identify the control plants of grid ac current control and dc current control. Analysis on the poles and zeros under dq frame is carried out. Base on this model, it turns out that the phase lag caused by the time delay can stabilized the grid ac current control while reduces...... the stable region for dc current control. Simulation and experimental results are presented to validate the theoretical analysis....

  20. Comparative evaluation of different strengths of electrical current in the management of dentinal hypersensitivity

    Directory of Open Access Journals (Sweden)

    Sandhu Sharn

    2010-01-01

    Full Text Available Background : Dentinal hypersensitivity is a commonly occurring but less understood and poorly managed problem of the teeth. Iontophoresis is a technique wherein desensitizing agents can be transferred under electrical pressure into the tooth structure to manage hypersensitivity. Aim : The purpose of present study is to compare the effect of different strengths of electrical current used for varying lengths of time, keeping the electrical dosage constant with the iontophoretic unit in the management of dentinal hypersensitivity. Materials and Methods : This study was conducted among the patients attending the Periodontal Department of the Government Dental College and Hospital, Patiala, Punjab, specifically complaining of tooth hypersensitivity. The Verbal Rating Scale (VRS was used to record scores pre-, during, and post-treatment. Ten percent SrCl2 solution was applied with an iontophoretic unit. Three applications were performed at weekly intervals, up to the second week, using the same electric current dosage. The data compiled was statistically analyzed. Results : A remarkable reduction in dentinal hypersensitivity to both air blast and cold water stimuli was noted at the end of two months after iontophoresis with each current group / method, namely, I (0.25 mA for 4 minutes, II (0.5 mA for 2 minutes, and III (1 mA for 1 minute. However, the differences in effectiveness / improvement within the three current groups during the entire duration of the study were found to be statistically insignificant. Conclusion : Within the limits of this study, it could be implied that for relieving hypersensitivity, iontophoresis for all three current groups was almost equally effective, and it was found that repeated applications (up to three gave good relief. Iontophoresis was found to be effective and safe.

  1. HVDC-AC system interaction from AC harmonics. Volume 1. Harmonic impedance calculations. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Breuer, G D; Chow, J H; Lindh, C B; Miller, N W; Numrich, F H; Price, W W; Turner, A E; Whitney, R R

    1982-09-01

    Improved methods are needed to characterize ac system harmonic behavior for ac filter design for HVDC systems. The purpose of this General Electric Company RP1138 research is to evaluate the present filter design practice and to investigate methods for calculating system harmonic impedances. An overview of ac filter design for HVDC systems and a survey of literature related to filter design have been performed. Two methods for calculating system harmonic impedances have been investigated. In the measurement method, an instrumentation system for measuring system voltage and current has been assembled. Different schemes of using the measurements to calculate system harmonic impedances have been studied. In the analytical method, a procedure to include various operating conditions has been proposed. Computer programs for both methods have been prepared, and the results of the measurement and analytical methods analyzed. A conclusion of the project is that the measurement and analytical methods both provided reasonable results. There are correlations between the measured and analytical results for most harmonics, although there are discrepancies between the assumptions used in the two methods. A sensitivity approach has been proposed to further correlate the results. From the results of the analysis, it is recommended that both methods should be tested further. For the measurement method, more testing should be done to cover different system operating conditions. In the analytical method, more detailed models for representing system components should be studied. In addition, alternative statistical and sensitivity approaches should be attempted.

  2. HVDC-AC system interaction from AC harmonics. Volume 1. Harmonic impedance calculations. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Breuer, G D; Chow, J H; Lindh, C B; Miller, N W; Numrich, F H; Price, W W; Turner, A E; Whitney, R R

    1982-09-01

    Improved methods are needed to characterize ac system harmonic behavior for ac filter design for HVDC systems. The purpose of this General Electric Company RP1138 research is to evaluate the present filter design practice and to investigate methods for calculating system harmonic impedances. An overview of ac filter design for HVDC systems and a survey of literature related to filter design have been performed. Two methods for calculating system harmonic impedances have been investigated. In the measurement method, an instrumentation system for measuring system voltage and current has been assembled. Different schemes of using the measurements to calculate system harmonic impedances have been studied. In the analytical method, a procedure to include various operating conditions has been proposed. Computer programs for both methods have been prepared, and the results of the measurement and analytical methods analyzed. A conclusion of the project is that the measurement and analytical methods both provided reasonable results. There are correlations between the measured and analytical results for most harmonics, although there are discrepancies between the assumptions used in the two methods. A sensitivity approach has been proposed to further correlate the results. From the results of the analysis, it is recommended that both methods should be tested further. For the measurement method, more testing should be done to cover different system operating conditions. In the analytical method, more detailed models for representing system components should be studied. In addition, alternative statistical and sensitivity approaches should be attempted.

  3. AcEST: DK943965 [AcEST

    Lifescience Database Archive (English)

    Full Text Available FKBP-type OS=Cya... 55 2e-06 tr|B8EIG1|B8EIG1_METSI Peptidylprolyl isomerase FKBP-type OS=Met... 53 9e-06 t... type OS=Ac... 51 4e-05 tr|B8I9L2|B8I9L2_METNO Peptidylprolyl isomerase FKBP-type OS=Met.

  4. Cascading failures in ac electricity grids

    Science.gov (United States)

    Rohden, Martin; Jung, Daniel; Tamrakar, Samyak; Kettemann, Stefan

    2016-09-01

    Sudden failure of a single transmission element in a power grid can induce a domino effect of cascading failures, which can lead to the isolation of a large number of consumers or even to the failure of the entire grid. Here we present results of the simulation of cascading failures in power grids, using an alternating current (AC) model. We first apply this model to a regular square grid topology. For a random placement of consumers and generators on the grid, the probability to find more than a certain number of unsupplied consumers decays as a power law and obeys a scaling law with respect to system size. Varying the transmitted power threshold above which a transmission line fails does not seem to change the power-law exponent q ≈1.6 . Furthermore, we study the influence of the placement of generators and consumers on the number of affected consumers and demonstrate that large clusters of generators and consumers are especially vulnerable to cascading failures. As a real-world topology, we consider the German high-voltage transmission grid. Applying the dynamic AC model and considering a random placement of consumers, we find that the probability to disconnect more than a certain number of consumers depends strongly on the threshold. For large thresholds the decay is clearly exponential, while for small ones the decay is slow, indicating a power-law decay.

  5. Introducing high performance distributed logging service for ACS

    Science.gov (United States)

    Avarias, Jorge A.; López, Joao S.; Maureira, Cristián; Sommer, Heiko; Chiozzi, Gianluca

    2010-07-01

    The ALMA Common Software (ACS) is a software framework that provides the infrastructure for the Atacama Large Millimeter Array and other projects. ACS, based on CORBA, offers basic services and common design patterns for distributed software. Every properly built system needs to be able to log status and error information. Logging in a single computer scenario can be as easy as using fprintf statements. However, in a distributed system, it must provide a way to centralize all logging data in a single place without overloading the network nor complicating the applications. ACS provides a complete logging service infrastructure in which every log has an associated priority and timestamp, allowing filtering at different levels of the system (application, service and clients). Currently the ACS logging service uses an implementation of the CORBA Telecom Log Service in a customized way, using only a minimal subset of the features provided by the standard. The most relevant feature used by ACS is the ability to treat the logs as event data that gets distributed over the network in a publisher-subscriber paradigm. For this purpose the CORBA Notification Service, which is resource intensive, is used. On the other hand, the Data Distribution Service (DDS) provides an alternative standard for publisher-subscriber communication for real-time systems, offering better performance and featuring decentralized message processing. The current document describes how the new high performance logging service of ACS has been modeled and developed using DDS, replacing the Telecom Log Service. Benefits and drawbacks are analyzed. A benchmark is presented comparing the differences between the implementations.

  6. AcMNPV-mediated expression of BmK IT promotes the apoptosis of Sf9 cells and replication of AcMNPV.

    Science.gov (United States)

    Fu, Yue-Jun; Zhao, Jie; Liang, Ai-Hua; Hu, Feng-Yun

    2015-06-25

    Chinese scorpion Buthus martensii Karsch (BmK) venom is a rich source of neurotoxins which bind to various ion channels with high affinity and specificity and thus widely used as compounds to modulate channel gating or channel currents. To promote the insecticidal effects of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), the gene encoding an excitatory insect toxin, BmK IT, was inserted into the genome of AcMNPV to construct a recombinant baculovirus, AcMNPV-BmK IT. Spodopter frugiperda 9 (Sf9) cells were infected with AcMNPV and AcMNPV-BmK IT respectively for 24 h. Results from the MTT assay, TUNEL assay, analysis of the expression level of apoptosis-related proteins (c-Myc, cleaved-Caspase3, Bcl-2 and Bax) of Sf9 cells, the transcription level of key genes (38K, C42, P78, F) of AcMNPV, and viral propagation assay demonstrated that AcMNPV-mediated expression of BmK IT promoted the apoptosis of Sf9 cells and replication of AcMNPV. The results laid a foundation for further structural and functional analysis of BmK IT.

  7. A Study of Characteristic of Short-Circuit Current Contributed by DC Systems With Single-Phase Short-Circuit Fault on AC Side%交流侧单相短路时直流系统提供短路电流的特性分析

    Institute of Scientific and Technical Information of China (English)

    王铁柱; 万磊; 张彦涛; 卜广全

    2016-01-01

    随着直流输电系统的迅速发展,能否忽略直流系统对短路电流的贡献成为一个亟待研究的问题。文章基于实际直流工程的详细电磁暂态模型,对交流侧发生单相短路故障时直流系统提供短路电流的特性进行研究。通过分析故障后直流输电系统的暂态特性,提出针对短路电流计算关键值,提取并分析直流系统提供短路电流的对应分量;通过对大量仿真结果的统计分析,明确了直流系统提供短路电流的特性及其对短路电流计算的影响,得出结论:直流系统提供的短路电流会使短路电流计算中的工频短路电流初始值、对称开断短路电流的幅值减小,而短路电流峰值增大,且工程应用中短路电流计算可以不考虑直流系统。通过基于实际电网的短路电流对比计算,验证了以上结论。%With rapid development of HVDC systems, it has become important to determine whether DC system contribution can be ignored in short-circuit (SC) current calculation. This paper studies characteristic of SC current contributed by DC systems with single-phase SC fault on AC Side, based on a detailed electromagnetic transient model. By analyzing transient process of a DC system during fault, it is proposed that certain components of SC current contributed by DC systems should be extracted and analyzed, corresponding to critical value of SC current calculation. Based on statistical analysis of a large number of simulation results, features of SC current contributed by DC systems are proposed, as well as its impact on SC current calculation. It is concluded that, SC current contributed by DC systems will decrease amplitude of initial symmetrical SC current and symmetrical breaking SC current, but will increase SC peak current, and that for engineering applications, DC system can be ignored in SC current calculation. Comparative calculation of SC current based on actual grid verifies above

  8. AC dynamometer; Koryu dinamo meter

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-01-10

    Fuji Electric Co., Ltd., developed an AC dynamometer for testing automobiles, and the product was delivered to Hokkaido Automotive Engineering College via Safety Automobile Company. The device is used for testing 1,300cc-class automobiles. It is similar to the conventional type in that its force of reaction to an imposed load is measured by load cells. It is a variable speed motor driven by an inverter (FRENIC5000VG5), whose specifications and features are mentioned below. It is a totally-enclosed self-cooled oscillating AC dynamometer that outputs 75kW, revolves at 1500/2868rpm, and operates for 30min. Since it is rated for a short time operation, the external fan is dispensed with, and this reduces noise. A number of parts for the standard type (R90 series) are utilized for reduction in the cost, and the time required for its delivery was short. (NEDO)

  9. Performance of AC/graphite capacitors at high weight ratios of AC/graphite

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Yoshio, Masaki [Advanced Research Center, Department of Applied Chemistry, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan)

    2008-03-01

    The effect of negative to positive electrode materials' weight ratio on the electrochemical performance of both activated carbon (AC)/AC and AC/graphite capacitors has been investigated, especially in the terms of capacity and cycle-ability. The limited capacity charge mode has been proposed to improve the cycle performance of AC/graphite capacitors at high weight ratios of AC/graphite. (author)

  10. 直流入地电流经交流电网分流计算模型的简化及算法分析%Model Simplication and Calculation Method Analysis About the Shunt of DC Grounding Current Via AC Grid

    Institute of Scientific and Technical Information of China (English)

    任志超; 吴广宁; 甄威; 吴超; 张一坤

    2011-01-01

    直流入地电流经交流电网分流的计算过程复杂,涉及到大范围地质分层结构.旨在简化计算模型,指出直流地电位分布与直流地电流分流的关系.首先分析了土层结构的Hummel法简化及其对地电位分布的影响;其次,研究了直流地电位分布规律及地电流分流特性;最后,讨论了直流通路等效电阻的构成,得出了直流地电位的计算方法.研究结果表明:当站点距离接地极较远时,土层简化可用于直流地电位计算;直流地电位在接地网附近小范围内会发生畸变,交流输电线的存在导致相连站点间的直流地电位差减小;接地极入地电流及复杂大地分层电阻可等效为电压源及电源内阻,在求解等效电压源电动势时,可利用贝塞尔函数的衰减余弦等价式取代无穷级数.%The calculation about the shunt of DC grounding current via AC grid is a complex process, involving a large range of geological hierarchical structure. To simplify the calculation model so as to put forward the relationship of the DC earth potential distribution and the shunt of DC grounding current, firstly, we analyzed the Hummel method by applying soil-layer structure simplification and its impact to the grounding potential distribution; secondly, we studied the law of the DC earth potential distribution and the characteristic of the shunt of DC grounding current; finally, we discussed the composition of equivalent resistance in the DC Pathway, and put forward the calculation method of DC earth potential. The results show that: the method of simplification layer can be adopted to calculate DC earth potential when the distance between substaions and DC grounding electrode is far enough. The distortion will occur nearby the grounding network in a small range, and the existence of AC transmission line will decrease the difference value of DC earth potential between the connected sites. The grounding current into the earth and complicated

  11. Fuzzy efficiency optimization of AC induction motors

    Science.gov (United States)

    Jani, Yashvant; Sousa, Gilberto; Turner, Wayne; Spiegel, Ron; Chappell, Jeff

    1993-01-01

    This paper describes the early states of work to implement a fuzzy logic controller to optimize the efficiency of AC induction motor/adjustable speed drive (ASD) systems running at less than optimal speed and torque conditions. In this paper, the process by which the membership functions of the controller were tuned is discussed and a controller which operates on frequency as well as voltage is proposed. The membership functions for this dual-variable controller are sketched. Additional topics include an approach for fuzzy logic to motor current control which can be used with vector-controlled drives. Incorporation of a fuzzy controller as an application-specific integrated circuit (ASIC) microchip is planned.

  12. Stretched exponential relaxation and ac universality in disordered dielectrics

    DEFF Research Database (Denmark)

    Milovanov, Alexander V.; Rypdal, Kristoffer; Juul Rasmussen, Jens

    2007-01-01

    This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues are stretc......This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues...... are stretched exponential character of dielectric relaxation, power-law power spectral density, and anomalous dependence of ac conduction coefficient on frequency. We propose a self-consistent model of dielectric relaxation in which the relaxations are described by a stretched exponential decay function....... Mathematically, our study refers to the expanding area of fractional calculus and we propose a systematic derivation of the fractional relaxation and fractional diffusion equations from the property of ac universality....

  13. AcEST: DK943968 [AcEST

    Lifescience Database Archive (English)

    Full Text Available = +2 Query: 71 SSIRDLDNSRPRAIACSDNSGICVAVAYNHLANM------AVATFRDKPSVHQAGS---M 223 SS+ S P AC+ N+ VA HL+N+ A+ F...ives = 24/56 (42%) Frame = +2 Query: 107 AIACSDNSGICVAVAYNHLANMAVATFRDKPSVHQAGSMN...es = 83/195 (42%), Gaps = 1/195 (0%) Frame = +2 Query: 32 VLTACSSGVYFWDSSIRDLDNSRPRAIACSDNSGICVAVAYNHLANMAVA.../188 (41%), Gaps = 2/188 (1%) Frame = +2 Query: 32 VLTACSSGVYFWDSSIRDLDNSRPRAIACSDNSGICVAVAYN-HLANMAVATFRDKP... VLTACSSGVYFWDSSIRDLDNSRPRAIACSDNSGICVAVAYN-HLANMAVATFRDKPSVH 208 V++A S G WD D +RP + +N G+C+++A N +++ VA+FR

  14. AcEST: DK954735 [AcEST

    Lifescience Database Archive (English)

    Full Text Available AC ■■Homology search results ■■ - Swiss-Prot (release 56.9) Link to BlastX Result : Swiss-Prot sp_hit_id Q7TMD5 Definition sp|Q7TMD5...ng significant alignments: (bits) Value sp|Q7TMD5|ZC3HE_RAT Zinc finger CCCH domain-containing protein 1... ...tein pstB ... 30 5.8 sp|Q2S081|PSTB_SALRD Phosphate import ATP-binding protein pstB O... 30 7.6 >sp|Q7TMD5

  15. A Switched Capacitor Based AC/DC Resonant Converter for High Frequency AC Power Generation

    Directory of Open Access Journals (Sweden)

    Cuidong Xu

    2015-09-01

    Full Text Available A switched capacitor based AC-DC resonant power converter is proposed for high frequency power generation output conversion. This converter is suitable for small scale, high frequency wind power generation. It has a high conversion ratio to provide a step down from high voltage to low voltage for easy use. The voltage conversion ratio of conventional switched capacitor power converters is fixed to n, 1/n or −1/n (n is the switched capacitor cell. In this paper, A circuit which can provide n, 1/n and 2n/m of the voltage conversion ratio is presented (n is stepping up the switched capacitor cell, m is stepping down the switching capacitor cell. The conversion ratio can be changed greatly by using only two switches. A resonant tank is used to assist in zero current switching, and hence the current spike, which usually exists in a classical switching switched capacitor converter, can be eliminated. Both easy operation and efficiency are possible. Principles of operation, computer simulations and experimental results of the proposed circuit are presented. General analysis and design methods are given. The experimental result verifies the theoretical analysis of high frequency AC power generation.

  16. Simulation of the Relaxation Potential Profile of an ac-dc-ac Test

    Directory of Open Access Journals (Sweden)

    Kerry N. Allahar

    2014-01-01

    Full Text Available The relaxation period of the accelerated ac-dc-ac test for coatings is associated with the transient electrochemistry that occurs when the immersed coated system is allowed to return to a stable open-circuit condition after being subjected to a cathodic potential. A mathematical model of the transient electrochemistry that occurs during this relaxation period is presented for coated aluminum. Expressions for the corrosion potential and corrosion current as functions of the local pH at the metal-coating interface were developed using reported experimental results. These expressions enabled the simulation of the transient electrochemistry under the constraint of balanced anodic and cathodic current densities. Regression of the transient relaxation potential profiles to exponential decay functions provided time-constant characterization of the profiles. Simulated results are presented that demonstrate the influences of the coating's porosity and thickness, the applied dc potential and the metal-coating interface condition on the time-constants associated with the relaxation profile. Interpretation of experimentally reported relaxation potential profiles supported the analysis of the simulated results.

  17. Faith and oscillations recovered: On analyzing EEG/MEG signals during tACS.

    Science.gov (United States)

    Neuling, Toralf; Ruhnau, Philipp; Weisz, Nathan; Herrmann, Christoph S; Demarchi, Gianpaolo

    2017-02-15

    Despite recent success in analyzing brain oscillations recorded during transcranial alternating current stimulation (tACS), the field still requires further research to establish standards in artifact removal methods. This includes taking a step back from the removal of the tACS artifact and thoroughly characterizing the to-be-removed artifact. A recent study by Noury et al. (2016) contributed importantly to this endeavour by showing the existence of nonlinear artefacts in the tACS signal as seen by MEG and EEG. Unfortunately however this paper conveys the message that current artifact removal attempts have failed altogether and that-based on these available tools-brain oscillations recorded during tACS cannot be analyzed using MEG and EEG. Here we want to balance this overly pessimistic conclusion: In-depth reanalyses of our own data and phantom-head measurements indicate that nonlinearities can occur, but only when technical limits of the stimulator are reached. As such they are part of the "real" stimulation and not a specific MEG analysis problem. Future tACS studies should consider these technical limits to avoid any nonlinear modulations of the tACS artifact. We conclude that even with current approaches, brain oscillations recorded during tACS can be meaningfully studied in many practical cases.

  18. AC Losses and Their Thermal Effect in High-Temperature Superconducting Machines

    DEFF Research Database (Denmark)

    Song, Xiaowei (Andy); Mijatovic, Nenad; Zou, Shengnan

    2016-01-01

    In transient operations or fault conditions, hightemperature superconducting (HTS) machines suffer ac losses, which have an influence on the thermal stability of superconducting windings. In this paper, a method to calculate ac losses and their thermal effect in HTS machines is presented....... The method consists of three submodels that are coupled only in one direction. The magnetic field distribution is first solved in a machine model, assuming a uniform current distribution in HTS windings. The magnetic fields on the boundaries are then used as inputs for an ac loss model that has a homogeneous...... approximation and solves the H formulation. Afterward, the computed ac losses are considered as the heat source in a thermal model to study the temperature profile in HTS windings. The method proposed is able to evaluate ac losses and their thermal effect, thus providing a reference to design an HTS machine...

  19. AC Losses and Their Thermal Effect in High Temperature Superconducting Machines

    DEFF Research Database (Denmark)

    Song, Xiaowei (Andy); Mijatovic, Nenad; Zou, Shengnan

    2015-01-01

    In transient operations or fault conditions, high temperature superconducting (HTS) machines suffer AC losses which have an influence on the thermal stability of superconducting windings. In this paper, a method to calculate AC losses and their thermal effect in HTS machines is presented. The met...... an HTS machine and its cooling system.......In transient operations or fault conditions, high temperature superconducting (HTS) machines suffer AC losses which have an influence on the thermal stability of superconducting windings. In this paper, a method to calculate AC losses and their thermal effect in HTS machines is presented....... The method consists of three sub-models that are coupled only in one direction. The magnetic field distribution is first solved in a machine model, assuming a uniform current distribution in HTS windings. The magnetic fields on the boundaries are then used as inputs for an AC loss model which has...

  20. Universality of ac conduction in disordered solids

    DEFF Research Database (Denmark)

    Dyre, Jeppe; Schrøder, Thomas

    2000-01-01

    The striking similarity of ac conduction in quite different disordered solids is discussed in terms of experimental results, modeling, and computer simulations. After giving an overview of experiment, a macroscopic and a microscopic model are reviewed. For both models the normalized ac conductivity...... as a function of a suitably scaled frequency becomes independent of details of the disorder in the extreme disorder limit, i.e., when the local randomly varying mobilities cover many orders of magnitude. The two universal ac conductivities are similar, but not identical; both are examples of unusual non......-power-law universalities. It is argued that ac universality reflects an underlying percolation determining dc as well as ac conductivity in the extreme disorder limit. Three analytical approximations to the universal ac conductivities are presented and compared to computer simulations. Finally, model predictions...

  1. Sensorless operation of surface mount permanent magnet AC (PMAC) motors

    Energy Technology Data Exchange (ETDEWEB)

    Toliyat, H.A.; Rahman, K.M.; Shet, D.S.

    1999-12-01

    A sensorless field oriented control scheme for surface mount permanent magnet ac (PMAC) motor with split phase stator windings is presented. This motor is obtained by splitting the phase windings of a conventional three phase motor. The six-phase motor, however is run as a three-phase motor by connecting the split phase stator windings in series, while the taps are made available for voltage measurements. By measuring the terminal voltages and the line currents, absolute position of the permanent magnet ac motor driven by a current regulated PWM inverter with a hysteresis controller is estimated. The estimated position information is independent of the stator resistance, thus this scheme is even applicable at low speeds. Results are presented to show the effectiveness of the new controller, and it is also shown that the position error is negligible.

  2. Transport signatures in topological systems coupled to ac fields

    Science.gov (United States)

    Ruocco, Leonard; Gómez-León, Álvaro

    2017-02-01

    We study the transport properties of a topological system coupled to an ac electric field by means of Floquet-Keldysh formalism. We consider a semi-infinite chain of dimers coupled to a semi-infinite metallic lead and obtain the density of states and current when the system is out of equilibrium. Our formalism is nonperturbative and allows us to explore, in the thermodynamic limit, a wide range of regimes for the ac field, arbitrary values of the coupling strength to the metallic contact and corrections to the wide-band limit (WBL). We find that hybridization with the contact can change the dimerization phase, and that the current dependence on the field amplitude can be used to discriminate between them. We also show the appearance of side bands and nonequilibrium zero-energy modes, characteristic of the Floquet systems. Our results directly apply to the stability of nonequilibrium topological phases, when transport measurements are used for their detection.

  3. Improved Tribological Performance of Amorphous Carbon (a-C Coating by ZrO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Jinzhu Tang

    2016-09-01

    Full Text Available Nanomaterials, such as Graphene, h-BN nanoparticles and MoS2 nanotubes, have shown their ability in improving the tribological performance of amorphous carbon (a-C coatings. In the current study, the effectiveness of ZrO2 nanoparticles (ZrO2-NPs in lubricating the self-mated nonhydrogenated a-C contacts was investigated in boundary lubrication regime. The results showed that 13% less friction and 50% less wear compared to the base oil were achieved by employing ZrO2-NPs in the base oil in self-mated a-C contacts. Via analyzing the ZrO2-NPs and the worn a-C surface after tests, it was found that the improved lubrication by ZrO2-NPs was based on “polishing effects”, which is a new phenomenon observed between a-C and nanoparticles. Under the “polishing effect”, micro-plateaus with extremely smooth surface and uniform height were produced on the analyzed a-C surface. The resulting topography of the a-C coating is suitable for ZrO2-NPs to act as nano-bearings between rubbing surfaces. Especially, the ZrO2-NPs exhibited excellent mechanical and chemical stability, even under the severe service condition, suggesting that the combination of nonhydrogenated a-C coating with ZrO2-NPs is an effective, long lasting and environment-friendly lubrication solution.

  4. Established and potential physiological roles of bicarbonate-sensing soluble adenylyl cyclase (sAC) in aquatic animals.

    Science.gov (United States)

    Tresguerres, Martin; Barott, Katie L; Barron, Megan E; Roa, Jinae N

    2014-03-01

    Soluble adenylyl cyclase (sAC) is a recently recognized source of the signaling molecule cyclic AMP (cAMP) that is genetically and biochemically distinct from the classic G-protein-regulated transmembrane adenylyl cyclases (tmACs). Mammalian sAC is distributed throughout the cytoplasm and it may be present in the nucleus and inside mitochondria. sAC activity is directly stimulated by HCO3(-), and sAC has been confirmed to be a HCO3(-) sensor in a variety of mammalian cell types. In addition, sAC can functionally associate with carbonic anhydrases to act as a de facto sensor of pH and CO2. The two catalytic domains of sAC are related to HCO3(-)-regulated adenylyl cyclases from cyanobacteria, suggesting the cAMP pathway is an evolutionarily conserved mechanism for sensing CO2 levels and/or acid/base conditions. Reports of sAC in aquatic animals are still limited but are rapidly accumulating. In shark gills, sAC senses blood alkalosis and triggers compensatory H(+) absorption. In the intestine of bony fishes, sAC modulates NaCl and water absorption. And in sea urchin sperm, sAC may participate in the initiation of flagellar movement and in the acrosome reaction. Bioinformatics and RT-PCR results reveal that sAC orthologs are present in most animal phyla. This review summarizes the current knowledge on the physiological roles of sAC in aquatic animals and suggests additional functions in which sAC may be involved.

  5. Control of grid interactive AC microgrids

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Guerrero, Josep M.; Chen, Zhe

    2010-01-01

    and reliability, becomes an attractive candidate for the configuration of future electrical power system. This paper gives a brief review of grid interactive ac microgrid configurations. Control methods for power electronics interfaced DER units in grid interactive ac microgrids are discussed. In addition......, microgrid controls and power management strategies are presented. Future trends of microgrid are discussed pointing out how this concept can be a key to achieve a more intelligent and flexible AC grid....

  6. Ac Synchronous Servo Based On The Armature Voltage Prediction Model

    Science.gov (United States)

    Hoshino, Akihiro; Kuromaru, Hiroshi; Kobayashi, Shinichi

    1987-10-01

    A new control method of the AC synchro-nous servo-system (Brushless DC servo-system) is discussed. The new system is based on the armature voltage prediction model. Without a resolver-digital-conver-ter nor a tachometer-generator, the resolver provides following three signals to the system immediately, they are the current command, the induced voltage, and the rotor speed. The new method realizes a simple hardware configuration. Experimental results show a good performance of the system.

  7. AcEST: DK959751 [AcEST

    Lifescience Database Archive (English)

    Full Text Available .. 86 1e-16 sp|A0FGR8|ESYT2_HUMAN Extended synaptotagmin-2 OS=Homo sapiens G... 72 3e-12 sp|Q6PFQ7|RASL2_MOU...SE Ras GTPase-activating protein 4 OS=Mus mus... 72 4e-12 sp|Q3TZZ7|ESYT2_MOUSE Extended...ivating-like protein 1 OS=Mus mu... 65 3e-10 sp|Q5M7N9|ESYT3_XENTR Extended synaptotagmin-3 OS=Xenopus tropi... 1 OS=Homo s... 61 6e-09 sp|Q8L7A4|AGD11_ARATH Probable ADP-ribosylation factor GTPase-ac... 61 6e-09 sp|Q7ZWU7|EST2B_XENLA Extended... synaptotagmin-2-B OS=Xenopus laev... 60 1e-08 sp|Q5FWL4|EST2A_XENLA Extended

  8. AcEST: BP920842 [AcEST

    Lifescience Database Archive (English)

    Full Text Available ta... 59 6e-09 sp|Q3TZZ7|ESYT2_MOUSE Extended synaptotagmin-2 OS=Mus musculus G... 59 7e-09 sp|Q9ZT47|PP16A_...CUCMA 16 kDa phloem protein 1 OS=Cucurbita maxim... 57 2e-08 sp|A0FGR8|ESYT2_HUMAN Extended synaptotagmin-2 ... domain-conta... 56 6e-08 sp|Q8L7A4|AGD11_ARATH Probable ADP-ribosylation factor GTPase-ac... 55 8e-08 sp|A0FGR9|ESYT3_HUMAN Extended... synaptotagmin-3 OS=Homo sapiens G... 55 1e-07 sp|Q5DTI8|ESYT3_MOUSE Extended synap...totagmin-3 OS=Mus musculus G... 54 2e-07 sp|Q5M7N9|ESYT3_XENTR Extended synaptota

  9. AcEST: DK956298 [AcEST

    Lifescience Database Archive (English)

    Full Text Available AIZE Glutamate dehydrogenase OS=Zea mays GN=GDH1... 370 e-102 sp|Q43314|DHE1_ARATH Glutamate dehydrogenase 1...HGK 202 >sp|P93541|DHE3_SOLLC Glutamate dehydrogenase OS=Solanum lycopersicum GN=GDH1 PE=2 SV=1 Length = 412...RG ++A EALL ++G+ Sbjct: 181 RDAATGRGALFATEALLNEHGK 202 >sp|Q43260|DHE3_MAIZE Glutamate dehydrogenase OS=Zea mays GN=GDH1...ATH Glutamate dehydrogenase 1 OS=Arabidopsis thaliana GN=GDH1 PE=1 SV=1 Length = 411 Score = 369 bits (946),...AC Glutamate dehydrogenase OS=Nicotiana taba... 376 e-103 tr|A7YVW3|A7YVW3_ACTCH GDH1 OS=Actinidia chinensis GN=GDH1

  10. Phase-sensitive detection of both inductive and non-inductive ac voltages in ferromagnetic resonance

    Science.gov (United States)

    Weiler, Mathias; Shaw, Justin M.; Nembach, Hans T.; Schoen, Martin A.; Boone, Carl T.; Silva, Thomas J.

    2014-03-01

    Spin pumping causes significant damping in ultrathin ferromagnetic/normal metal (NM) multilayers via spin-current generation of both dc and ac character in the NM system. While the nonlinear dc component has been investigated in detail by utilization of the inverse spin Hall effect (iSHE) in NMs, much less is known about the linear ac component that is presumably much larger in the small-excitation limit. We measured generated ac voltages in a wide variety of Permalloy/NM multilayers via vector-network-analyzer ferromagnetic resonance. We employ a custom, impedance-matched, broadband microwave coupler that features a ferromagnetic thin film reference resonator to accurately compare ac voltage amplitudes and phases between varieties of multilayers. By use of the fact that inductive and ac iSHE signals are phase-shifted by π/2, we find that inductive signals are major contributors in all investigated samples. It is only by comparison of the phase and amplitude of the recorded ac voltages between multiple samples that we can extract the non-inductive contributions due to spin-currents. Voltages due to the ac iSHE in Permalloy(10nm)/platinum(5nm) bilayers are weaker than inductive signals, in agreement with calculations based upon recent theoretical predictions. M.W. acknowledges financial support by the German Academic Exchange service (DAAD).

  11. Analysis of Physics Processes in the AC Plasma Torch Discharge under High Pressure

    Science.gov (United States)

    Safronov, A. A.; Vasilieva, O. B.; Dudnik, J. D.; E Kuznetsov, V.; Kuchina, J. A.; Shiryaev, V. N.; Pavlov, A. V.

    2017-04-01

    The paper is devoted to investigation of electrophysical processes in the electric discharge generated by a three-phase AC plasma torch when using a high pressure inert working gas. AC plasma torch design with end electrodes intended for work on inert gases at pressures up to 81 bar is studied. Current-voltage characteristics for different gas flow rates and pressures are presented. Physical processes characteristics of the arising voltage ripples which depend on various working parameters of the plasma torch have been investigated. Arc burning processes in the electric discharge chamber of the three-phase AC plasma torch at various working parameters were photographed.

  12. Investigation of the Coupling Paths of a Galvanically Isolated AC/AC Converter

    NARCIS (Netherlands)

    Roc'h, Anne; Zhao, Dongsheng; Leferink, Frank; Polinder, Henk; Ferreira, Braham

    2007-01-01

    A galvanically isolated three-phase AC/AC converter with a high-frequency AC-link has been analyzed from an EMC point of view. This is a special configuration because of a large number of switches, a high frequency transformer, and a fourwire output. The essential coupling paths are identified. Corr

  13. AcCNET (Accessory Genome Constellation Network): comparative genomics software for accessory genome analysis using bipartite networks.

    Science.gov (United States)

    Lanza, Val F; Baquero, Fernando; de la Cruz, Fernando; Coque, Teresa M

    2017-01-15

    AcCNET (Accessory genome Constellation Network) is a Perl application that aims to compare accessory genomes of a large number of genomic units, both at qualitative and quantitative levels. Using the proteomes extracted from the analysed genomes, AcCNET creates a bipartite network compatible with standard network analysis platforms. AcCNET allows merging phylogenetic and functional information about the concerned genomes, thus improving the capability of current methods of network analysis. The AcCNET bipartite network opens a new perspective to explore the pangenome of bacterial species, focusing on the accessory genome behind the idiosyncrasy of a particular strain and/or population.

  14. Computations of AC Loss in the ITER Magnets during Fast Field Transients

    CERN Document Server

    Bottura, Luca; Lister, Jonathan B; Marinucci, Claudio; Portone, Alfredo

    2007-01-01

    The calculation of AC loss due to the control currents in ITER is a cumbersome task. The reason is that control transients require small field changes (0.1 T or less) at moderate frequency (up to 10 Hz), where effects of partial penetration of the filaments and shielding are important and need to be taken into account to produce sound AC loss estimates. In this paper we describe models developed for AC loss calculation, in particular hysteresis and coupling current loss, that are suitable for the above regime. Both hysteresis and coupling loss models are adapted to the conductor analyzed through few parameters (the effective filament diameter and time constants) that can be derived from measurement of loss on short samples. We report an example of calculations of AC loss in the ITER TF and PF coils for two vertical control scenarios (VS1 and VS2) during high beta operation at flattop.

  15. AC polarographic determination of cloxacillin.

    Science.gov (United States)

    Núñez-Vergara, L J; Silva, M M; Squella, J A

    1982-11-01

    Hydrolysis of cloxacillin at pH 4.0 yields an electroactive product which can be determined by polarography. Depending on the concentration of cloxacillin, one of 2 peaks was obtained: The potential ac peaks for a 4.36 mM cloxacillin solution were peak I, -0.23 V and peak II, -0.13 V. For analytical purposes, the first peak was used. A linear relationship was established for levels of cloxacillin between 2.2 X 10(-5) and 2.2 X 10(-3)M. Average recovery was 98.8% (SD 1.8), indicating satisfactory accuracy for the method. Individual capsule and composite assays as well as interference tests are described.

  16. System and method for monitoring and controlling stator winding temperature in a de-energized AC motor

    Science.gov (United States)

    Lu, Bin; Luebke, Charles John; Habetler, Thomas G.; Zhang, Pinjia; Becker, Scott K.

    2011-12-27

    A system and method for measuring and controlling stator winding temperature in an AC motor while idling is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of a multi-phase AC motor. The circuit further includes a plurality of switching devices to control current flow and terminal voltages in the multi-phase AC motor and a controller connected to the circuit. The controller is configured to activate the plurality of switching devices to create a DC signal in an output of the motor control device corresponding to an input to the multi-phase AC motor, determine or estimate a stator winding resistance of the multi-phase AC motor based on the DC signal, and estimate a stator temperature from the stator winding resistance. Temperature can then be controlled and regulated by DC injection into the stator windings.

  17. Flame spread over inclined electrical wires with AC electric fields

    KAUST Repository

    Lim, Seung J.

    2017-07-21

    Flame spread over polyethylene-insulated electrical wires was studied experimentally with applied alternating current (AC) by varying the inclination angle (θ), applied voltage (VAC), and frequency (fAC). For the baseline case with no electric field applied, the flame spread rate and the flame width of downwardly spreading flames (DSFs) decreased from the horizontal case for −20° ≤ θ < 0° and maintained near constant values for −90° ≤ θ < −20°, while the flame spread rate increased appreciably as the inclination angle of upwardly spreading flames (USFs) increased. When an AC electric field was applied, the behavior of flame spread rate in DSFs (USFs) could be classified into two (three) sub-regimes characterized by various functional dependences on VAC, fAC, and θ. In nearly all cases of DSFs, a globular molten polyethylene formed ahead of the spreading flame edge, occasionally dripping onto the ground. In these cases, an effective flame spread rate was defined to represent the burning rate by measuring the mass loss due to dripping. This effective spread rate was independent of AC frequency, while it decreased linearly with voltage and was independent of the inclination angle. In DSFs, when excessively high voltage and frequency were applied, the dripping led to flame extinction during propagation and the extinction frequency correlated well with applied voltage. In USFs, when high voltage and frequency were applied, multiple globular molten PEs formed at several locations, leading to ejections of multiple small flame segments from the main flame, thereby reducing the flame spread rate, which could be attributed to the electrospray phenomenon.

  18. AC-tabsmodeller for superledende kabelledere

    DEFF Research Database (Denmark)

    Østergaard, Jacob; Holm (fratrådt), Jesper; Understrup (fratrådt), Henriette

    1996-01-01

    I denne rapport opstilles tre modeller for beregning af AC-tab (vekselstrømstab) i superledende kabelledere. Beregning af tabenes størrelse er væsentlig i forbindelse med vurdering af superlederteknologiens anvendelighed til AC-applikationer. Viden om tabenes natur giver desuden et vigtigt...

  19. Regular structures in 5CB liquid crystals under the joint action of ac and dc voltages

    Science.gov (United States)

    Aguirre, Luis E.; Anoardo, Esteban; Éber, Nándor; Buka, Ágnes

    2012-04-01

    A nematic liquid crystal with high, positive dielectric anisotropy (5CB) has been studied under the influence of the combined action of a dc and an ac electric field. Broad frequency, voltage, and cell thickness ranges were considered. Pattern morphologies were identified; the thresholds and critical wave numbers were measured and analyzed as a function of frequency, dc-to-ac voltage ratio, and thickness. The current-voltage characteristics were simultaneously detected.

  20. AC conductivity and dielectric properties of Co-doped TiO 2

    Science.gov (United States)

    Okutan, Mustafa; Basaran, Engin; Bakan, Halil I.; Yakuphanoglu, Fahrettin

    2005-07-01

    The alternating current (AC) conductivity and dielectric properties of the Co-doped TiO 2 were investigated. The temperature dependence of AC conductivity and the parameter s, is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energy ( E), and the density of states at Fermi level, N( EF) were determined. The dielectric constant decreases with frequency at low frequencies and increases at high frequencies.

  1. AC conductivity and dielectric properties of Co-doped TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Okutan, Mustafa [Department of Physics, Gebze Institute of Technology, P.O. Box 141, 41400 Gebze (Turkey)]. E-mail: mustafa@gyte.edu.tr; Basaran, Engin [Department of Physics, Gebze Institute of Technology, P.O. Box 141, 41400 Gebze (Turkey); Bakan, Halil I. [TUBITAK-MAM, Materials and Chemical Research Institute, 41470 Gebze (Turkey); Yakuphanoglu, Fahrettin [Department of Physics, Faculty of Arts and Science, Firat University, 23169 Elazig (Turkey)

    2005-07-15

    The alternating current (AC) conductivity and dielectric properties of the Co-doped TiO{sub 2} were investigated. The temperature dependence of AC conductivity and the parameter s, is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energy (E), and the density of states at Fermi level, N(E {sub F}) were determined. The dielectric constant decreases with frequency at low frequencies and increases at high frequencies.

  2. Offshore Wind Park Connection to an HVDC Platform, without using an AC Collector Platform

    OpenAIRE

    Ahmad, Haseeb

    2012-01-01

    This thesis investigates the comparison between two different alternating current topologies of an offshore wind farms connection to an offshore high voltage direct current (HVDC) converter platform. The offshore high voltage direct current converter platform converts alternating current into direct current. Two different topologies will be investigated. In the first topology, the offshore wind farms are connected to an HVDC converter platform through offshore AC collector platform. An offsho...

  3. AC Conductivity and Dielectric Properties of Borotellurite Glass

    Science.gov (United States)

    Taha, T. A.; Azab, A. A.

    2016-10-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  4. AcEST: BP916793 [AcEST

    Lifescience Database Archive (English)

    Full Text Available SC complexes subunit ssr2 OS=S... 66 6e-14 sp|Q9XI07|SWI3C_ARATH SWI/SNF complex subunit SWI3C OS=Arabidops...... 65 1e-12 sp|Q8VY05|SWI3D_ARATH SWI/SNF complex subunit SWI3D OS=Arabidops... 66 2e-12 sp|P97496|SMRC1_MOU...2|SWI3B_ARATH SWI/SNF complex subunit SWI3B OS=Arabidops... 59 9e-09 sp|Q8W475|SWI3A_ARATH SWI/SNF complex s...ional adapter ADA2 OS=Oryza sati... 47 3e-05 sp|Q9ATB4|TAD2B_ARATH Transcriptional adapter ADA2b OS=Arabidops...... 45 2e-04 sp|Q9SFD5|TAD2A_ARATH Transcriptional adapter ADA2a OS=Arabidops... 44 3e-04 sp|Q5ZJF3|TAD2A_C

  5. Analysis on Phase Arrangement and Transposition Modes for UHV DC and Double-circuit EHV AC Transmission Line Built on the Same Tower

    Institute of Scientific and Technical Information of China (English)

    SIMA Wenxia; ZHOU Yuan; YUAN Tao; YANG Qing; SUN Shujie; Gilles Tremouille

    2012-01-01

    For AC and DC hybrid transmission lines, the arrangement and transposition modes of AC conductors not only affect the unbalance factor of AC lines, but also influence the bias current of DC converter transformers by AC and DC coupling. Excessive bias current will influence the normal operation of converter transformers, thus the optimal AC phase arrangement and transposition mode of hybrid lines was studied to minimize the coupling effect between AC and DC lines to fit the requirements on both aspects. Based on the parameters of the Ximeng-Shanghai project in China, a detailed simulation model of the DC converter station and the hybrid transmission line with double- circuit AC 500 kV transmission lines and DC ± 800 kV transmission lines were presented in the software PSCAD- EMTDC, and the coupling effects of the hybrid transmission lines were elucidated. The fundamental frequency components of DC poles with different operation conditions, arrangements of conductors and operation modes were analyzed, and the effective arrangement and transposition limiting the fundamental frequency current component of the DC line were compared. Simulation results show that AC operating conditions can affect DC induced components while the DC system operation mode has no apparent effect. With compact arrangement and inconsistent transposition of AC lines, the fundamental frequency component on DC lines can be reduced effectively; the three transposed mode within the hybrid line is the optimal layout scheme, considering both the requirements of DC bias current and AC unbalance degree.

  6. Effective nonlinear AC response to composite with spherical particles

    Institute of Scientific and Technical Information of China (English)

    Chen Xiao-Gang; Liang Fang-Chu; Wei En-Bo

    2005-01-01

    An effective nonlinear alternative-current (AC) response to granular nonlinear-composite with spherical inclusions embedded in a host medium under the action of an external AC field is investigated by using a perturbation approach.The local potentials of composite at higher harmonics are derived both in a region of local inclusion particles and in a local host region under the action of a sinusoidal field E1 sinωt + E3sin3ωt. An effective nonlinear-response to composite and the relationship between the effective nonlinear-responses at the fundamental frequency and the third harmonics are also studied for the spherical inclusions in a dilute limit.

  7. Effects of AC Coils Parameters on Transduction Efficiency of EMAT for Steel Plate Inspection

    Directory of Open Access Journals (Sweden)

    Xiaochun Song

    2014-01-01

    Full Text Available In order to improve the transduction efficiency of electromagnetic acoustic transducer (EMAT for steel plates inspection, the constitutive equation of magnetostrictive material was theoretically derived and simplified while the magnetostrictive force is parallel to the material surface. Based on the multiphysics field FEM, the effects of such excitation parameters as current, frequency, and pulse number in AC coils on magnetostrictive strain were mainly simulated, and the influence of the coil with different winding shapes on magnetostrictive strain was also analyzed. The simulation and experimental results indicate that magnetostrictive strain increases with a continuously increasing excitation current density, but it decreases with the increase of the frequency and pulse number of AC currents. Moreover, on condition that loop length and AC currents are held constant, spiral type coils have higher transduction efficiency than homocentric squares and figure-of-eight coils.

  8. Effective AC needleless and collectorless electrospinning for yarn production.

    Science.gov (United States)

    Pokorny, P; Kostakova, E; Sanetrnik, F; Mikes, P; Chvojka, J; Kalous, T; Bilek, M; Pejchar, K; Valtera, J; Lukas, D

    2014-12-28

    Nanofibrous materials are essential components for a wide range of applications, particularly in the fields of medicine and material engineering. These include protective materials, sensors, cosmetics, hygiene, filtration and energy storage. The most widely used and researched technology in these fields is electrospinning. This method for producing fibers yields highly promising results thanks to its versatility and simplicity. Electrospinning is employed in multiple forms, among which needle and needleless direct current (DC) variants are the most distinctive. The former is based on the generation of just one single jet from a nozzle; hence this fabrication process is not very productive. The latter uses the destabilization of free liquid surfaces by means of an electric field, which enhances the throughput since it produces numerous jets, emitted from the surfaces of rollers, spheres, strings and spirals. However, although some progress in total producibility has been achieved, the efficiency of the DC method still remains relatively low. A further drawback of DC electrospinning is that both variants need a collector, which makes it difficult to combine DC electrospinning easily with other technologies due to the presence of the high field strength within the entire spinning zone. This paper describes our experiments with AC electrospinning. We show that alternating current (AC) electrospinning based on a needleless spinning-electrode provides a highly productive smoke-like aerogel composed of nanofibers. This aerogel rises rapidly from the electrode like a thin plume of smoke, without any need for a collector. Our work shows that AC needleless electrospinning gains its efficiency and collector-less feature thanks to the creation of a perpetually charge-changing virtual counter-electrode composed of the nanofibers emitted. High-speed camera recordings demonstrate the formation mechanism of the nanofibrous plume, which is wafted by an electric wind. This wind

  9. Three-phase AC-AC power converters based on matrix converter topology matrix-reactance frequency converters concept

    CERN Document Server

    Szczesniak, Pawel

    2013-01-01

    AC voltage frequency changes is one of the most important functions of solid state power converters. The most desirable features in frequency converters are the ability to generate load voltages with arbitrary amplitude and frequency, sinusoidal currents and voltages waveforms; the possibility of providing unity power factor for any load; and, finally, a simple and compact power circuit. Over the past decades, a number of different frequency converter topologies have appeared in the literature, but only the converters with either a voltage or current DC link are commonly used in industrial app

  10. Effects of AC Electric Field on Small Laminar Nonpremixed Flames

    KAUST Repository

    Xiong, Yuan

    2015-04-01

    Electric field can be a viable method in controlling various combustion properties. Comparing to traditional actuators, an application of electric field requires very small power consumption. Especially, alternating current (AC) has received attention recently, since it could modulate flames appreciably even for the cases when direct current (DC) has minimal effects. In this study, the effect of AC electric fields on small coflow diffusion flames is focused with applications of various laser diagnostic techniques. Flow characteristics of baseline diffusion flames, which corresponds to stationary small coflow diffusion flames when electric field is not applied, were firstly investigated with a particular focus on the flow field in near-nozzle region with the buoyancy force exerted on fuels due to density differences among fuel, ambient air, and burnt gas. The result showed that the buoyancy force exerted on the fuel as well as on burnt gas significantly distorted the near-nozzle flow-fields. In the fuels with densities heavier than air, recirculation zones were formed very close to the nozzle exit. Nozzle heating effect influenced this near-nozzle flow-field particularly among lighter fuels. Numerical simulations were also conducted and the results showed that a fuel inlet boundary condition with a fully developed velocity profile for cases with long fuel tubes should be specified inside the fuel tube to obtain satisfactory agreement in both the flow and temperature fields with those from experiment. With sub-critical AC applied to the baseline flames, particle image velocimetry (PIV), light scattering, laser-induced incandescence (LII), and laser-induced fluores- cence (LIF) techniques were adopted to identify the flow field and the structures of OH, polycyclic aromatic hydrocarbons (PAHs), soot zone. Under certain AC condi- tions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered from the

  11. Direct current power delivery system and method

    Science.gov (United States)

    Zhang, Di; Garces, Luis Jose; Dai, Jian; Lai, Rixin

    2016-09-06

    A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

  12. Memory effect in ac plasma displays

    Science.gov (United States)

    Szlenk, K.; Obuchowicz, E.

    1993-10-01

    The bistable or `memory' mode of operation of an ac plasma display panel is presented. The difference between dc and ac plasma panel operation from the point of view of memory function is discussed. The graphic ac plasma display with thin film Cr-Cu-Cr electrodes was developed in OBREP and its basic parameters are described. It consists of 36 X 59 picture elements, its outer dimensions are: 76 X 52 mm2 and the screen size is: 49 X 30 mm2. The different dielectric glass materials were applied as dielectric layers and the influence of the properties of these materials on display parameters and memory function was investigated.

  13. Numeric description of space charge in polyethylene under ac electric fields

    Science.gov (United States)

    Zhao, J.; Xu, Z.; Chen, G.; Lewin, P. L.

    2010-12-01

    Space charge in polyethylene-based insulation materials and its effect on the local electric field under a dc environment have been extensively examined over the last few decades while the behavior of space charge under ac stress has received less attention. Space charge phenomenon under ac electric fields becomes an important issue with increased operating field strength in many applications, such as next generation high voltage cables. In this paper, a bipolar charge transport model has been developed to simulate space charge in polymers under ac electric fields. Obtained simulation results show that there is a small quantity of phase-dependent bipolar charge accumulation in the vicinity of the electrodes that does not move into the bulk under ac stress. This causes a slight distortion of the local field in the bulk. However, at lower frequencies less than 1 Hz, there is increased charge accumulation and penetration. Comparison with available experimental data suggests that the model is capable of describing the underlying physics of charge behavior when a dielectric material is subjected to ac electric fields. Due to the weak charge movement in the bulk, the conduction current density is small and hence the displacement component dominates the total current density and this increases linearly with ac frequency.

  14. AC Impedance Studies on Metal/Nanoporous Silicon/p-Silicon Structures

    Science.gov (United States)

    Mabrook, M. F.; Ray, A. K.

    2016-11-01

    Alternating current (AC) impedance measurements have been performed on 10- to 15-μm thick porous silicon layers on a (100) p-type silicon (p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz-1 MHz and in the temperature ranging between 152 K and 292 K. The ac conductivity σ ac was found to increase with frequency f according to the universal power law: σ_{ac} = Afs where the exponent s is a frequency and temperature-dependent quantity. A hopping process is found to be dominant at low temperatures and high frequencies, while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of the loss tangent is observed with a temperature-dependent minimum value.

  15. System and Battery Charge Control for PV-Powered AC Lighting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Kern, G.

    1999-04-01

    This report reviews a number of issues specific to stand-alone AC lighting systems. A review of AC lighting technology is presented, which discusses the advantages and disadvantages of various lamps. The best lamps for small lighting systems are compact fluorescent. The best lamps for intermediate-size systems are high- or low-pressure sodium. Specifications for battery charging and load control are provided with the goal of achieving lamp lifetimes on the order of 16,000 to 24,000 hours and battery lifetimes of 4 to 5 years. A rough estimate of the potential domestic and global markets for stand-alone AC lighting systems is presented. DC current injection tests were performed on high-pressure sodium lamps and the test results are presented. Finally, a prototype system was designed and a prototype system controller (with battery charger and DC/AC inverter) was developed and built.

  16. Giant magnetoimpedance effect of ac-dc Joule annealed electroplated NiFe/Cu composite wires

    Energy Technology Data Exchange (ETDEWEB)

    Ghanaatshoar, M.; Shokri, B. [Laser and Plasma Research Institute, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Azad, N. [Laser and Plasma Research Institute, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Faculty of Science, Imam Khomeini International University, Qazvin (Iran, Islamic Republic of); Banitaba, M.H. [Departments of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran (Iran, Islamic Republic of)

    2011-11-15

    In this article, we investigate the influence of ac-dc Joule annealing of NiFe microtubes on their giant magnetoimpedance effect. NiFe magnetic layers were electroplated onto 100-{mu}m-diameter copper wires and then submitted to dc or ac-dc current annealing for 8 minutes. Both annealing and cooling down processes were performed in argon atmosphere. Results show that the presence of ac part of Joule treatment leads to higher induced anisotropy and increases the MI ratio. It is conjectured that the ac component through wall movement and moment fluctuation increases the tendency of the magnetic domains to lie circumferentially. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Pharmacological characterization of AC-262536, a novel selective androgen receptor modulator.

    Science.gov (United States)

    Piu, Fabrice; Gardell, Luis R; Son, Thomas; Schlienger, Nathalie; Lund, Birgitte W; Schiffer, Hans H; Vanover, Kim E; Davis, Robert E; Olsson, Roger; Bradley, Stefania Risso

    2008-03-01

    Because of the limitations and liabilities of current testosterone therapies, non-steroidal tissue-selective androgen receptor modulators may provide a clinically meaningful advance in therapy. Using a functional cell-based assay AC-262536 was identified as a potent and selective AR ligand, with partial agonist activity relative to the natural androgen testosterone. A 2-week chronic study in castrated male rats indicated that AC-262536 significantly improves anabolic parameters in these animals, especially in stimulating the growth of the levator ani and in suppressing elevated LH levels. In sharp contrast to testosterone, AC-262536 has weak androgenic effects, as measured by prostate and seminal vesicle weights. Thus, AC-262536 represents a novel class of selective androgen receptor modulators (SARMs) with beneficial anabolic effects.

  18. Stability Enhancement of Power System by Controlling Hvdc Power Flow through the Same Ac Transmission Line

    Directory of Open Access Journals (Sweden)

    P. Upendra Kumar

    2014-04-01

    Full Text Available Long extra high voltage (EHV ac lines cannot be loaded to their thermal limits in order to keep sufficient margin against transient instability. With the scheme proposed in this paper, it is possible to load these lines very close to their thermal limits. The conductors are allowed to carry usual ac along with dc superimposed on it. The added dc power flow does not cause any transient instability. This paper presents the feasibility of converting a double circuit ac line into composite ac–dc power transmission line to get the advantages of parallel ac–dc transmission to improve stability and damping out oscillations. Simulation and experimental studies are carried out for the coordinated control as well as independent control of ac and dc power transmissions. No alterations of conductors, insulator strings, and towers of the original line are needed. Substantial gain in the loadability of the line is obtained. Master current controller senses ac current and regulates the dc current orders for converters online such that conductor current never exceeds its thermal limit. The present paper is implemented by using MATLAB/SIMULINK.

  19. AC losses in superconductors with a power-law constitutive relation

    Energy Technology Data Exchange (ETDEWEB)

    Agassi, Y.D., E-mail: yehoshua.agassi@navy.mil

    2015-10-15

    Highlights: • Derivation of power-law constitutive-relation from distributed Anderson–Kim theory. • The electric-field for HTS constitutive-relation satisfies nonlinear heat-equation. • For slab, AC losses scale as B{sub 0}{sup m}, m = 3–4 and I{sup 3} with field-amplitude and current, respectively. • Calculated pinning potential, AC-losses scaling is consistent with BSCCO data. - Abstract: The observed constitutive relation between the electrical field and current density in cuprates high temperature superconductors is a power-law of the current. This functional dependence is presumably related to the giant flux-creep domain. It is shown that this constitutive relation reflects the statistical spread of the pinning potential associated with creep motion of vortex bundles. The AC losses emanating from a power-law constitutive relation are calculated in an approach focused on the superconductor’s electric field. For a slab geometry in the presence of a parallel AC magnetic field or transport current, the calculated AC-loss scaling laws are consistent with BSCCO data and the critical state model. Extensions of the approach are briefly discussed.

  20. Hysteretic ac losses in a superconductor strip between flat magnetic shields

    Energy Technology Data Exchange (ETDEWEB)

    Genenko, Y A; Rauh, H, E-mail: hera@tgm.tu-darmstadt.d [Institut fuer Materialwissenschaft, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany)

    2010-07-15

    Hysteretic ac losses in a thin, current-carrying superconductor strip located between two flat magnetic shields of infinite permeability are calculated using Bean's model of the critical state. Exact numerical calculations and approximate analytical forms delineating the penetration of magnetic flux and the energy dissipated during a cycle of the ac transport current, per unit length of the strip, are derived. For the shields oriented parallel to the plane of the strip, the penetration of the self-induced magnetic field is found to be enhanced, with the analytical current dependence of the ac loss conditionally resembling that of an isolated superconductor slab; for the shields oriented perpendicular to the plane of the strip, the penetration of the self-induced magnetic field is found to be impaired, with the analytical current dependence of the ac loss conditionally duplicating that of a regular set of curved superconducting tapes extending longitudinally around a surface of cylindrical shape. Thus, hysteretic ac losses can strongly augment or, respectively, wane when the shields approach the strip.

  1. DC-Modulated PFC Buck-Type AC/AC Converter for Light Dimming

    Institute of Scientific and Technical Information of China (English)

    罗方林; 叶虹

    2007-01-01

    Dimmers are very widely applied in theatres, cinemas, dancing-parties, auditoriums and signal systems. They are usually supplied by single-stage AC/AC converters in the past with voltage regulation technique with the disadvantages of high total harmonic distortion, low power factor and poor power transfer efficiency. This paper introduces a novel method-DC-modulation that implements DC/DC conversion technology into AC/AC converters. The DC-modulated single-stage PFC AC/AC converters effectively improved the power factor up to 0.999 and the power transfer efficiency up to 97.8 %. The experimental results verified our design and calculation. This technique will be widely used in light dimming and other industrial applications.

  2. AC-driven organic light emission devices with carbon nanotubes

    Science.gov (United States)

    Jeon, So-Yeon; Yu, SeGi

    2017-02-01

    We have investigated alternating current (AC)-driven organic light-emitting devices (OLEDs), with carbon nanotubes (CNTs) incorporated within the emission layer. With CNT incorporation, the brightness of the OLEDs was substantially improved, and the turn-on voltage was reduced by at least a factor of five. Furthermore, the current levels of the CNT-incorporated OLEDs were lower than that of the reference device. A roughly 70% decrease in the current level was obtained for a CNT concentration of 0.03 wt%. This was accomplished by keeping the concentration of CNTs low and the length of CNTs short, which helped to suppress the percolation networking of CNTs within the emitting layer. Strong local electric fields near the end-tips of CNTs and micro-capacitors formed by dispersed CNTs might have caused this high brightness and these low currents. CNT incorporation in the emitting layer can improve the characteristics of AC-driven OLEDs, which are considered to be one of the candidates for flat panel displays and lightning devices.

  3. Measurement of AC losses in different former materials

    DEFF Research Database (Denmark)

    Olsen, Søren Krüger; Træholt, Chresten; Kühle, Anders Van Der Aa

    1998-01-01

    A high temperature superconducting cable may be based on a centrally located cylindrical support, a so-called former. If electrically conductive, the former can contribute to the AC losses through eddy current losses caused by unbalanced axial and tangential magnetic fields. With these measurements...... we aim at investigating the eddy current losses of commonly used former materials. A one layer cable conductor was wound on a glass fibre reinforced polymer (GRFP) former. By inserting a variety of materials into this, it was possible to measure the eddy current losses of each of the former...... candidates separately; for example copper tubes, stainless steel braid, copper braid, corrugated stainless steel tubes, etc. The measured data are compared with the predictions of a theoretical model. Our results show that in most cases, the losses induced by eddy currents in the former are negligible...

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

    KAUST Repository

    Xiong, Yuan

    2014-09-22

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

  5. Power Controllability of Three-phase Converter with Unbalanced AC Source

    DEFF Research Database (Denmark)

    Ma, Ke; Chen, Wenjie; Liserre, Marco

    2015-01-01

    Three-phase DC-AC power converters suffer from power oscillation and overcurrent problems in case of unbalanced AC source voltage that can be caused by grid/generator faults. Existing solutions to handle these problems are properly selecting and controlling the positive and negative sequence...... currents. In this work a new series of control strategies which utilize the zerosequence components are proposed to enhance the power control ability under this adverse condition. It is concluded that by introducing proper zero sequence current controls and corresponding circuit configurations, the power...... converter can enable more flexible control targets, achieving better performances in the delivered power and load current when suffering from unbalanced AC voltage....

  6. Power Controllability of Three-phase Converter with Unbalanced AC Source

    DEFF Research Database (Denmark)

    Ma, Ke; Liserre, Marco; Blaabjerg, Frede

    2013-01-01

    Three-phase DC-AC power converters suffer from power oscillation and overcurrentt problems in case of unbalanced AC source voltage that can be caused by grid/generator faults. Existing solutions to handle these problems are properly selecting and controlling the positive and negative sequence...... converter can enable more flexible control targets, achieving better performances in the delivered power and load current when suffering from unbalanced AC sources....... currents. In this work a new series of control strategies which utilize the zero-sequence components are proposed to enhance the power control ability under this adverse conditions. It is concluded that by introducing proper zero sequence current controls and corresponding circuit configurations, the power...

  7. Cooperative Frequency Control for Autonomous AC Microgrids

    DEFF Research Database (Denmark)

    Shafiee, Qobad; Quintero, Juan Carlos Vasquez; Guerrero, Josep M.

    2015-01-01

    Distributed secondary control strategies have been recently studied for frequency regulation in droop-based AC Microgrids. Unlike centralized secondary control, the distributed one might fail to provide frequency synchronization and proportional active power sharing simultaneously, due to having...... not require measuring the system frequency as compared to the other presented methods. An ac Microgrid with four sources is used to verify the performance of the proposed control methodology....

  8. 马士基将重组AC-2和AC-3航线

    Institute of Scientific and Technical Information of China (English)

    燕翔(整理)

    2014-01-01

    马士基航运将重组其远东-墨西哥-中美洲-南美洲西海岸航线“AC-2”线和“AC-3”线。“AC-2”线将延伸至华北和韩国,同时不再挂靠华南,在亚洲,该航线将加挂青岛和釜山,

  9. 电渗作用对替硝唑经皮离子导入的影响%Effect of Electroosmosis on Iontophoretic Transdermal Delivery of Tinidazole

    Institute of Scientific and Technical Information of China (English)

    高建青; 冯璇; 梁文权

    2001-01-01

    考察了电场下电渗作用对分子型药物替硝唑经皮渗透的影响。实验结果表明,替硝唑从饱和水溶液经正极导入时,透皮速率比其被动扩散增加12.8倍,负极导入也产生一定的促进作用。替硝唑的透皮速率随电流强度而增加。另外,NaCl的加入使得电场下替硝唑的透皮速率明显下降,而在NaCl浓度为0.05 mol/L时药物在电场下的透皮速率相对较大。%The effect of electroosmosis on the transdermal delivery of molecular drug——tinidazole was investigated. The results showed that the flux of tinidazole saturated water solution with anodal iontophoresis was 12.8 times as great as the passive flux and cathodal iontophoresis also showed a certain enhance effect. The transdermal flux of tinidazole increased with the increasing of current intensity. On the other hand, added NaCl could decrease the tinidazole flux under the electric field and the relatively larger flux appeared at the NaCl concentration of 0.05 mol/L.

  10. Method and system for a gas tube-based current source high voltage direct current transmission system

    Energy Technology Data Exchange (ETDEWEB)

    She, Xu; Chokhawala, Rahul Shantilal; Bray, James William; Sommerer, Timothy John; Zhou, Rui; Zhang, Di

    2017-08-29

    A high-voltage direct-current (HVDC) transmission system includes an alternating current (AC) electrical source and a power converter channel that includes an AC-DC converter electrically coupled to the electrical source and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and the DC-AC inverter each include a plurality of legs that includes at least one switching device. The power converter channel further includes a commutating circuit communicatively coupled to one or more switching devices. The commutating circuit is configured to "switch on" one of the switching devices during a first portion of a cycle of the H-bridge switching circuits and "switch off" the switching device during a second portion of the cycle of the first and second H-bridge switching circuits.

  11. imulation Results of Single Stage AC- AC Converter for Induction Heating

    Directory of Open Access Journals (Sweden)

    S. ARUMUGAM

    2010-12-01

    Full Text Available This paper presents simulation of single stage Induction heating system with series Load Resonance. Low frequency AC is converted in to High Frequency Ac using newly developed ZVS-PWM high frequency inverter. This High Frequency is used for Induction Heating .Single stage AC-AC converter system is modeled and simulated using Matlab Simulink. The simulation results of ZVS-PWM high frequency system are presented. The effectiveness of this UFAC-to-HFAC direct power frequency converter using IGBTs for consumer high-frequency IH appliances is evaluated and proved on the basis of simulation results.

  12. AC-conductance of a non-local Thirring model

    Energy Technology Data Exchange (ETDEWEB)

    Trobo, Marta Liliana; Von Reichenbach, Maria Cecilia [Universidad Nacional de La Plata (UNLP) (Argentina); Barci, Daniel G. [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)]|[Illinois Univ., Urbana, IL (United States); Medeiros Neto, J.F. de [Universidade Estadual de Santa Cruz (UESC), Ilheus, BA (Brazil)

    2000-07-01

    Full text follows: In recent years renewed interest has arisen in the study of low dimensional field theories. In particular, research on the one dimensional (1-d) fermionic gas has been very active, mainly due to the actual nano-fabrication of the so called quantum wires and their relevance for low dimensional condensed matter physics as, for instance, the quantum Hall effect and high-T{sub c} superconductivity. Experimental and theoretical investigations of the AC-transport phenomena in nano-structures are of profound scientific interest since they provide insight into the behavior of quantum systems. In this frame, we consider a field theoretical approach that can be used to describe a system of 1-d strongly correlated particles in the low transferred momentum limit. We study a non-local and non-covariant version of the Thirring model where the fermionic densities and currents are coupled through bilocal, distance-dependent potentials which describe the forward scattering processes. We apply the functional bosonization formalism, a very useful technique to understand the non-perturbative regime of strongly correlated one-dimensional fermionic systems, to this non local Thirring like model (NLTM). We are interesting in the transport properties of the system, in particular in the AC-conductance. To this end, we consider a NLTM in the presence of an external electromagnetic field. We obtain the AC-conductance of the model in terms of non-local potentials used to describe the interactions between fermionic currents. We also analyze the transport properties in the case in which weak couplings between fermionic currents and localized impurities are taken into account. (author)

  13. A predictive model of the temperature dependence of AC transport losses in (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} tapes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Guomin; Lin Liangzhen; Xiao Liye; Yu Yunjia [Key Laboratory of Applied Superconductivity, Chinese Academy of Sciences, Beijing 100190 (China); Schwartz, Justin [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Pamidi, Sastry V [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States)

    2011-08-15

    Critical currents and AC losses of (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} superconducting tapes were measured in self-field as a function of temperature. The experimental data of the temperature dependence of critical current were compared with calculated results. An approach to calculating AC losses as a function of temperature was developed and the calculated AC losses were compared with the measured data. The study shows that AC losses at any temperature can be estimated using the model from the critical parameters or from the measured AC loss factor at a certain temperature, such as 77 K.

  14. 78 FR 39345 - ACS Wireless, Inc.; Notice of Application

    Science.gov (United States)

    2013-07-01

    ... No. 812-14066] ACS Wireless, Inc.; Notice of Application AGENCY: Securities and Exchange Commission... (``Act''). Summary of Application: ACS Wireless, Inc. (``ACS Wireless'') seeks an order under section 3(b..., reinvesting, owning, holding or trading in securities. ACS Wireless is primarily engaged in providing...

  15. 21 CFR 886.1850 - AC-powered slitlamp biomicroscope.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered slitlamp biomicroscope. 886.1850... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1850 AC-powered slitlamp biomicroscope. (a) Identification. An AC-powered slitlamp biomicroscope is an AC-powered device that is...

  16. 21 CFR 886.4440 - AC-powered magnet.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  17. 21 CFR 888.1240 - AC-powered dynamometer.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered dynamometer. 888.1240 Section 888.1240...) MEDICAL DEVICES ORTHOPEDIC DEVICES Diagnostic Devices § 888.1240 AC-powered dynamometer. (a) Identification. An AC-powered dynamometer is an AC-powered device intended for medical purposes to...

  18. 21 CFR 886.1630 - AC-powered photostimulator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered photostimulator. 886.1630 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1630 AC-powered photostimulator. (a) Identification. An AC-powered photostimulator is an AC-powered device intended to provide light stimulus...

  19. The dependence of AC loss characteristics on the space in stacked YBCO conductors

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Zhenan [Department of Electrical and Computer Engineering, Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501 (Japan); Amemiya, Naoyuki [Department of Electrical and Computer Engineering, Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501 (Japan); Kakimoto, Kazuomi [Materials Research Laboratory, Fujikura Ltd, 1-5-1 Kiba, Koto, Tokyo 135-8512 (Japan); Iijima, Yasuhiro [Materials Research Laboratory, Fujikura Ltd, 1-5-1 Kiba, Koto, Tokyo 135-8512 (Japan); Saitoh, Takashi [Materials Research Laboratory, Fujikura Ltd, 1-5-1 Kiba, Koto, Tokyo 135-8512 (Japan); Shiohara, Yuh [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto, Tokyo 135-0062 (Japan)

    2008-01-15

    Four 5 mm wide YBCO conductors were assembled face to face to obtain a stacked YBCO conductor (YBCO stack). The space between the conductors composing the YBCO stack was set at 1.0 mm to investigate the influence of the space on AC loss characteristics. The magnetization losses without transport current, the transport losses without external magnetic field, and total AC losses of the YBCO stack carrying various transport currents in transverse magnetic fields with various orientations were measured. The measured AC losses in the YBCO stack were compared with those in a 0.2 mm space YBCO stack composed of the same conductors used in the 1.0 mm space YBCO stack as well as a single YBCO conductor. Magnetization loss without transport current in a YBCO stack decreases with decreasing space between the conductors in low and intermediate magnetic field. Transport loss without external magnetic field in a YBCO stack increases with decreasing space between conductors. There are three characterized regions, when comparing the total AC losses in the two YBCO stacks with different space between the conductors composing the stacks: (a) in the low magnetic field region, the total AC losses in the YBCO stack with smaller space are larger than those in the YBCO stack with larger space, (b) in the intermediate magnetic field region, the total AC losses in the YBCO stack with smaller space are larger than those in the YBCO stack with larger space, (c) in the high magnetic field region, the total AC losses in both YBCO stacks agree well with those in the single YBCO conductor as well as Brandt and Indembom's analytical values.

  20. Materials for Powder-Based AC-Electroluminescence

    Directory of Open Access Journals (Sweden)

    Hubert Schulze Dieckhoff

    2010-02-01

    Full Text Available At present, thick film (powder based alternating current electroluminescence (AC-EL is the only technology available for the fabrication of large area, laterally structured and coloured light sources by simple printing techniques. Substrates for printing may be based on flexible polymers or glass, so the final devices can take up a huge variety of shapes. After an introduction of the underlying physics and chemistry, the review highlights the technical progress behind this development, concentrating on luminescent and dielectric materials used. Limitations of the available materials as well as room for further improvement are also discussed.

  1. Unbalanced Voltage Compensation in Low Voltage Residential AC Grids

    DEFF Research Database (Denmark)

    Trintis, Ionut; Douglass, Philip; Munk-Nielsen, Stig

    2016-01-01

    This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling....... The voltage control was evaluated with either active or reactive independent phase load current control. The control performance in field operation in a residential grid situated in Bornholm, Denmark was investigated for different use cases....

  2. Ag incorporated Mn3O4/AC nanocomposite based supercapacitor devices with high energy density and power density.

    Science.gov (United States)

    Nagamuthu, S; Vijayakumar, S; Muralidharan, G

    2014-12-14

    Silver incorporated Mn3O4/amorphous carbon (AC) nanocomposites are synthesized by a green chemistry method. X-ray diffraction studies revealed the structural changes in Mn3O4/AC nanocomposites attributable to the addition of silver. Cyclic voltammetry, charge-discharge and ac-impedance studies indicated that the Ag-Mn3O4/AC-5 electrode was the most suitable candidate for supercapacitor applications. From the galvanostatic charge-discharge studies, a higher specific capacitance of 981 F g(-1) at a specific current of 1 A g(-1) was obtained. An Ag-Mn3O4/AC-symmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as an anode as well as a cathode, and an asymmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as a cathode and an activated carbon as an anode have been fabricated. The symmetric device exhibits a specific cell capacitance of 72 F g(-1) at a specific current of 1 A g(-1) whereas the asymmetric device delivers a specific cell capacitance of 180 F g(-1) at a high current rate of 10 A g(-1). The asymmetric supercapacitor device yields a high energy density of 81 W h kg(-1). This is higher than that of lead acid batteries and comparable with that of nickel hydride batteries.

  3. Effect of Modulated Alternating and Direct Current Iontophoresis on Transdermal Delivery of Lidocaine Hydrochloride

    Directory of Open Access Journals (Sweden)

    Gaurav Bhatia

    2014-01-01

    Full Text Available The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87±120.03 μg/sq·cm compared to 744.81±125.41 μg/sq·cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27±18.71 μg/sq·cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h.

  4. Effect of modulated alternating and direct current iontophoresis on transdermal delivery of lidocaine hydrochloride.

    Science.gov (United States)

    Bhatia, Gaurav; Banga, Ajay K

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87 ± 120.03 μ g/sq · cm compared to 744.81 ± 125.41 μ g/sq · cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27 ± 18.71 μ g/sq · cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h.

  5. The influence of time-variable cathodic corrosion protection on a.c. corrosion; Einfluss von zeitlich variierendem kathodischem Korrosionsschutz auf die Wechselstromkorrosion

    Energy Technology Data Exchange (ETDEWEB)

    Buechler, Markus; Voute, Carl-Heinz; Joos, David [SGK Schweizerische Gesellschaft fuer Korrosionsschutz, Zuerich (Switzerland)

    2011-07-01

    The current limiting values for corrosion of pipelines under a.c. current stress may be difficult to apply to pipelines, owing to the very heterogeneous bedding of the pipeline, poor jacket quality, or high short-term a.c. voltages. In principle, periodic alternation between very high and very low protective currents may optimize cathodic corrosion protection. This pulsed current strategy was found to be effective in laboratory tests if the operating parameters are set accurately.

  6. Evaluation of constant current alternating current iontophoresis for transdermal drug delivery.

    Science.gov (United States)

    Yan, Guang; Li, S Kevin; Higuchi, William I

    2005-12-10

    Previous studies in our laboratory have demonstrated that alternating current (AC) iontophoresis can significantly decrease skin electric resistance and enhance the transport of charged permeants across skin. Flux variability of neutral permeants during AC iontophoresis was also found to be less than that of conventional direct current (DC) iontophoresis. The objectives of the present study were to evaluate flux enhancement of constant current AC transdermal iontophoresis and compare the AC flux with that of constant current DC iontophoresis. Iontophoresis studies of AC amplitude of 1, 2, and 5 mA were conducted in side-by-side diffusion cells with donor solution of 0.015, 0.15, and 1.0 M tetraethylammonium (TEA) chloride and receiver solution of phosphate buffered saline (PBS) using human epidermal membrane (HEM). Conventional constant current DC iontophoresis of 0.2 mA was also performed under similar conditions. TEA and mannitol were the model permeants. The following are the major findings in the present study. The flux of TEA increased proportionally with the AC current for all three TEA chloride concentrations and at the AC frequency used in the present study. When the permeant and its counter ion were the only ionic species in the donor chamber, the fluxes during DC iontophoresis were weakly dependent of its donor concentration. The fluxes of TEA during constant current AC iontophoresis were moderately related to the donor concentration with the highest TEA flux observed under the 1.0 M TEA chloride condition although the relationship between flux and donor concentration was not linear. A trend of decreasing electroosmotic transport with increasing donor TEA chloride concentration was observed with significant sample-to-sample variability during DC iontophoresis. Mannitol permeability was also observed to decrease with increasing TEA chloride concentration in the donor under the AC conditions, but data variability under AC was significantly smaller than that

  7. Defining phosphor luminescence property requirements for white AC LED flicker reduction

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Jianchuan; Narendran, Nadarajah, E-mail: narenn2@rpi.edu

    2015-11-15

    In this paper, we investigate the luminescence of slow-decay phosphors under flickering excitation from an alternating current light-emitting diode (AC LED). A mathematical model was developed to predict the behavior of slow-decay phosphors. The model predictions were validated by experiment. Results showed that it is possible to achieve good quality white light with low flicker index from an AC LED with a slow-decay phosphor. A human factors study confirmed the potential of slow-decay phosphors to improve acceptability of the light output from AC LEDs. Based on this study, we propose a set of recommendations for slow-decay phosphor luminescence properties to create a white AC LED with minimal flicker. - Highlights: • A mathematical model was proposed to simulate slow-decay phosphors. • The behavior of slow-decay phosphors under an AC LED excitation was simulated. • Slow-decay phosphor properties recommended to achieve low flicker, white AC LED. • A human factors study validated the flicker reduction by slow-decay phosphor.

  8. Fibrillar disruption by AC electric field induced oscillation: A case study with human serum albumin.

    Science.gov (United States)

    Sen, Shubhatam; Chakraborty, Monojit; Goley, Snigdha; Dasgupta, Swagata; DasGupta, Sunando

    2017-07-01

    The effect of oscillation induced by a frequency-dependent alternating current (AC) electric field to dissociate preformed amyloid fibrils has been investigated. An electrowetting-on-dielectric type setup has been used to apply the AC field of varying frequencies on preformed fibrils of human serum albumin (HSA). The disintegration potency has been monitored by a combination of spectroscopic and microscopic techniques. The experimental results suggest that the frequency of the applied AC field plays a crucial role in the disruption of preformed HSA fibrils. The extent of stress generated inside the droplet due to the application of the AC field at different frequencies has been monitored as a function of the input frequency of the applied AC voltage. This has been accomplished by assessing the morphology deformation of the oscillating HSA fibril droplets. The shape deformation of the oscillating droplets is characterized using image analysis by measuring the dynamic changes in the shape dependent parameters such as contact angle and droplet footprint radius and the amplitude. It is suggested that the cumulative effects of the stress generated inside the HSA fibril droplets due to the shape deformation induced hydrodynamic flows and the torque induced by the intrinsic electric dipoles of protein due to their continuous periodic realignment in presence of the AC electric field results in the destruction of the fibrillar species. Copyright © 2017. Published by Elsevier B.V.

  9. Calorimetric method of ac loss measurement in a rotating magnetic field.

    Science.gov (United States)

    Ghoshal, P K; Coombs, T A; Campbell, A M

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-T(c) superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  10. The Sloan Lens ACS Survey. V. The full ACS strong-lens sample

    NARCIS (Netherlands)

    Bolton, Adam S.; Burles, Scott; Koopmans, Leon V. E.; Treu, Tommaso; Gavazzi, Raphael; Moustakas, Leonidas A.; Wayth, Randall; Schlegel, David J.

    2008-01-01

    We present the definitive data for the full sample of 131 strong gravitational lens candidates observed with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope by the Sloan Lens ACS (SLACS) Survey. All targets were selected for higher redshift emission lines and lower redshift

  11. The Sloan Lens ACS Survey. V. The full ACS strong-lens sample

    NARCIS (Netherlands)

    Bolton, Adam S.; Burles, Scott; Koopmans, Leon V. E.; Treu, Tommaso; Gavazzi, Raphael; Moustakas, Leonidas A.; Wayth, Randall; Schlegel, David J.

    2008-01-01

    We present the definitive data for the full sample of 131 strong gravitational lens candidates observed with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope by the Sloan Lens ACS (SLACS) Survey. All targets were selected for higher redshift emission lines and lower redshift c

  12. Approaches to building single-stage AC/AC conversion switch-mode audio power amplifiers

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2004-01-01

    This paper discusses the possible topologies and promising approaches towards direct single-phase AC-AC conversion of the mains voltage for audio applications. When compared to standard Class-D switching audio power amplifiers with a separate power supply, it is expected that direct conversion...

  13. AC loss characterization of single pancake BSCCO coils by measured different methods

    Science.gov (United States)

    Safran, Serap; Souc, Jano; Gömöry, Fedor

    2017-10-01

    Electromagnetic measurements for AC losses of single pancake BSCCO coils and tapes have been performed experimentally as a function of reinforcement material, number of turns and AC current. Two coils have been prepared with using isolated Bi2Sr2Ca2Cu3O10/Ag (BSCCO) tape produced by Sumitomo Electric Industries, Ltd. For the experimental tests, the pancake coil is immersed in liquid nitrogen bath. The critical current Icp is determined. The transport AC loss has been measured by electromagnetic and calorimetric method using a lock-in amplifier. In electromagnetic method, the signal from 1) whole coil voltage, 2) the pair of taps placed in the 1/3 outer turn and 3) 3 cm long contactless loop placed in the 1/3 outer turn making a C shaped loop, are measured. Increasing the number of turns in the pancake increases the dissipation per unit length of the tape.

  14. Model of Bi-directional Flyback Converter for Hybrid AC/DC Distribution System

    Directory of Open Access Journals (Sweden)

    Riku Pasonen

    2013-12-01

    Full Text Available In this article, a simulation model and concept of two switch bi-directional isolated DC/DC converter is presented. Converter is based on flyback converter type. Also control method for voltage regulation with bi-directional power transfer is presented. Target application of the proposed converter was selected to be a hybrid AC/DC distribution system concept of which was briefly described. The requirement of galvanic isolation in the hybrid AC/DC concept comes from use of shared neutral wire; DC current runs with unbalanced part of AC current in neutral wire. Without galvanic isolation grounded neutral would cause short circuit if DC/DC converter is connected to three phase rectifier or inverter. Simulation was carried out with PSCAD electromagnetic transient simulator.

  15. Electric field in an AC dielectric barrier discharge overlapped with a nanosecond pulse discharge

    Science.gov (United States)

    Goldberg, Benjamin M.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.

    2016-08-01

    The effect of ns discharge pulses on the AC barrier discharge in hydrogen in plane-to-plane geometry is studied using time-resolved measurements of the electric field in the plasma. The AC discharge was operated at a pressure of 300 Torr at frequencies of 500 and 1750 Hz, with ns pulses generated when the AC voltage was near zero. The electric field vector is measured by ps four-wave mixing technique, which generates coherent IR signal proportional to the square of electric field. Absolute calibration was done using an electrostatic (sub-breakdown) field applied to the discharge electrodes, when no plasma was generated. The results are compared with one-dimensional kinetic modeling of the AC discharge and the nanosecond pulse discharge, predicting behavior of both individual micro-discharges and their cumulative effect on the electric field distribution in the electrode gap, using stochastic averaging based on the experimental micro-discharge temporal probability distribution during the AC period. Time evolution of the electric field in the AC discharge without ns pulses, controlled by a superposition of random micro-discharges, exhibits a nearly ‘flat top’ distribution with the maximum near breakdown threshold, reproduced quite well by kinetic modeling. Adding ns pulse discharges on top of the AC voltage waveform changes the AC discharge behavior in a dramatic way, inducing transition from random micro-discharges to a more regular, near-1D discharge. In this case, reproducible volumetric AC breakdown is produced at a well-defined moment after each ns pulse discharge. During the reproducible AC breakdown, the electric field in the plasma exhibits a sudden drop, which coincides in time with a well-defined current pulse. This trend is also predicted by the kinetic model. Analysis of kinetic modeling predictions shows that this effect is caused by large-volume ionization and neutralization of surface charges on the dielectrics by ns discharge pulses. The present

  16. AC/DC and DC/AC Converty Circuits in Power Supply Equipment%电源设备中AC/DC和DC/AC变换电路

    Institute of Scientific and Technical Information of China (English)

    杨碧石

    2001-01-01

    电源设备中根据电路变换功能来看,可分为四种类型:AC/DC、DC/AC、DC/DC、AC/AC,本文对AC/DC、DC/AC这两种变换的工作原理进行分析阐述并讨论每种电路的应用领域.

  17. DC-Compensated Current Transformer.

    Science.gov (United States)

    Ripka, Pavel; Draxler, Karel; Styblíková, Renata

    2016-01-20

    Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component.

  18. AC susceptibilities of grain-textured superconductors

    Science.gov (United States)

    Sakamoto, N.; Fukuda, Y.; Koga, M.; Akune, T.; Khan, H. R.; Lüders, K.

    2008-09-01

    In-phase χ n‧ and out-phase χ n″ components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field Bdc, an amplitude Ba and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low- Tc metallic superconductors, χ1‧ shows smooth transition and χ1″ does single peak. High- Tc oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in χ1″ and shoulders in χ1‧ appear in AC susceptibility of Hg-1223 superconductors. Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.

  19. Interior point algorithm-based power flow optimisation of a combined AC and DC multi-terminal grid

    Directory of Open Access Journals (Sweden)

    Farhan Beg

    2015-01-01

    Full Text Available The high cost of power electronic equipment, lower reliability and poor power handling capacity of the semiconductor devices had stalled the deployment of systems based on DC (multi-terminal direct current system (MTDC networks. The introduction of voltage source converters (VSCs for transmission has renewed the interest in the development of large interconnected grids based on both alternate current (AC and DC transmission networks. Such a grid platform also realises the added advantage of integrating the renewable energy sources into the grid. Thus a grid based on DC MTDC network is a possible solution to improve energy security and check the increasing supply demand gap. An optimal power solution for combined AC and DC grids obtained by the solution of the interior point algorithm is proposed in this study. Multi-terminal HVDC grids lie at the heart of various suggested transmission capacity increases. A significant difference is observed when MTDC grids are solved for power flows in place of conventional AC grids. This study deals with the power flow problem of a combined MTDC and an AC grid. The AC side is modelled with the full power flow equations and the VSCs are modelled using a connecting line, two generators and an AC node. The VSC and the DC losses are also considered. The optimisation focuses on several different goals. Three different scenarios are presented in an arbitrary grid network with ten AC nodes and five converter stations.

  20. Low-frequency ac electroporation shows strong frequency dependence and yields comparable transfection results to dc electroporation.

    Science.gov (United States)

    Zhan, Yihong; Cao, Zhenning; Bao, Ning; Li, Jianbo; Wang, Jun; Geng, Tao; Lin, Hao; Lu, Chang

    2012-06-28

    Conventional electroporation has been conducted by employing short direct current (dc) pulses for delivery of macromolecules such as DNA into cells. The use of alternating current (ac) field for electroporation has mostly been explored in the frequency range of 10kHz-1MHz. Based on Schwan equation, it was thought that with low ac frequencies (10Hz-10kHz), the transmembrane potential does not vary with the frequency. In this report, we utilized a flow-through electroporation technique that employed continuous 10Hz-10kHz ac field (based on either sine waves or square waves) for electroporation of cells with defined duration and intensity. Our results reveal that electropermeabilization becomes weaker with increased frequency in this range. In contrast, transfection efficiency with DNA reaches its maximum at medium frequencies (100-1000Hz) in the range. We postulate that the relationship between the transfection efficiency and the ac frequency is determined by combined effects from electrophoretic movement of DNA in the ac field, dependence of the DNA/membrane interaction on the ac frequency, and variation of transfection under different electropermeabilization intensities. The fact that ac electroporation in this frequency range yields high efficiency for transfection (up to ~71% for Chinese hamster ovary cells) and permeabilization suggests its potential for gene delivery.

  1. Iontophoretic drug delivery across the nail.

    Science.gov (United States)

    Delgado-Charro, Maria Begoña

    2012-01-01

    Topical drug delivery to treat nail diseases such as onychomycosis and psoriasis is receiving increasing attention. Topical nail delivery is challenged by the complicated structure of the nail and the low permeability of most drugs across the nail plate. Considerable effort has been directed at developing methods to promote drug permeation across the nail plate. Iontophoresis efficiently enhances molecular transport across the skin and the eye and is now being tested for its potential in ungual delivery. This review covers the basic mechanisms of transport (electro-osmosis and -migration) and their relative contribution to nail iontophoresis as well as the key factors governing nail permselectivity and ionic transport numbers. Methodological issues concerning research in this area are summarized. The data available in vivo on nail iontophoresis of terbinafine specifically are reviewed in separate sections. Our understanding of nail iontophoresis has improved considerably since 2007; most decisively, the feasibility of nail iontophoresis in vivo has been clearly demonstrated. Future work is required to establish the adequate implementation of the technique so that its clinical efficacy to treat onychomycosis and nail psoriasis can be unequivocally determined.

  2. Nuclear structure of {sup 231}Ac

    Energy Technology Data Exchange (ETDEWEB)

    Boutami, R. [Instituto de Estructura de la Materia, CSIC, Serrano 113 bis, E-28006 Madrid (Spain); Borge, M.J.G. [Instituto de Estructura de la Materia, CSIC, Serrano 113 bis, E-28006 Madrid (Spain)], E-mail: borge@iem.cfmac.csic.es; Mach, H. [Department of Radiation Sciences, ISV, Uppsala University, SE-751 21 Uppsala (Sweden); Kurcewicz, W. [Department of Physics, University of Warsaw, Pl-00 681 Warsaw (Poland); Fraile, L.M. [Departamento Fisica Atomica, Molecular y Nuclear, Facultad CC. Fisicas, Universidad Complutense, E-28040 Madrid (Spain); ISOLDE, PH Department, CERN, CH-1211 Geneva 23 (Switzerland); Gulda, K. [Department of Physics, University of Warsaw, Pl-00 681 Warsaw (Poland); Aas, A.J. [Department of Chemistry, University of Oslo, PO Box 1033, Blindern, N-0315 Oslo (Norway); Garcia-Raffi, L.M. [Instituto de Fisica Corpuscular, CSIC - Universidad de Valencia, Apdo. 22805, E-46071 Valencia (Spain); Lovhoiden, G. [Department of Physics, University of Oslo, PO Box 1048, Blindern, N-0316 Oslo (Norway); Martinez, T.; Rubio, B.; Tain, J.L. [Instituto de Fisica Corpuscular, CSIC - Universidad de Valencia, Apdo. 22805, E-46071 Valencia (Spain); Tengblad, O. [Instituto de Estructura de la Materia, CSIC, Serrano 113 bis, E-28006 Madrid (Spain); ISOLDE, PH Department, CERN, CH-1211 Geneva 23 (Switzerland)

    2008-10-15

    The low-energy structure of {sup 231}Ac has been investigated by means of {gamma} ray spectroscopy following the {beta}{sup -} decay of {sup 231}Ra. Multipolarities of 28 transitions have been established by measuring conversion electrons with a MINI-ORANGE electron spectrometer. The decay scheme of {sup 231}Ra {yields}{sup 231}Ac has been constructed for the first time. The Advanced Time Delayed {beta}{gamma}{gamma}(t) method has been used to measure the half-lives of five levels. The moderately fast B(E1) transition rates derived suggest that the octupole effects, albeit weak, are still present in this exotic nucleus.

  3. The ACS Nearby Galaxy Survey Treasury

    CERN Document Server

    Dalcanton, Julianne J; Seth, Anil C; Dolphin, Andrew; Holtzman, Jon; Rosema, Keith; Skillman, Evan D; Cole, Andrew; Girardi, Leo; Gogarten, Stephanie M; Karachentsev, Igor D; Olsen, Knut; Weisz, Daniel; Christensen, Charlotte; Freeman, Ken; Gilbert, Karoline; Gallart, Carme; Harris, Jason; Hodge, Paul; de Jong, Roelof S; Karachentseva, Valentina; Mateo, Mario; Stetson, Peter B; Tavarez, Maritza; Zaritsky, Dennis; Governato, Fabio; Quinn, Thomas

    2009-01-01

    The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both t he ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.

  4. AC optik - visuaalisen identiteetin suunnittelu optikkoliikkeelle

    OpenAIRE

    Valén, Wilma

    2017-01-01

    Toteutin opinnäytetyöni yhdessä pienen loviisalaisen optikkoliikkeen, AC optikin kanssa. Opinnäytetyössäni suunnittelen AC optikille uuden visuaalisen ilmeen ja brändätyn pakkauksen, jossa silmälasit ja oheistavara on helppo luovuttaa asiakkaalle. Taustoitan aihettani yksityisyrittäjälle tärkeistä näkökulmista eli keskittymällä positiivisen asiakaskokemuksen tärkeyteen brändin rakentamisessa. Sen lisäksi käyn läpi visuaalisen identiteetin suunnittelun elementtejä ja pakkauksen asemaa brän...

  5. AC410 Unit 2 Homework Assignment

    OpenAIRE

    Laynebaril1

    2017-01-01

      AC410 Unit 2 Homework Assignment Click Link Below To Buy: http://hwcampus.com/shop/ac410-unit-2-homework-assignment/   3-31 Ron Barber, CPA, is auditing the financial statements of DGF, Inc., a publicly held company. During the course of the audit, Barber discovered that DGF has been making illegal bribes to foreign government officials to obtain business, and he reported the matter to senior management and the board of directors of DGF. Required: If management a...

  6. Control of Power Converters in AC Microgrids

    DEFF Research Database (Denmark)

    Rocabert, Joan; Luna, Alvaro; Blaabjerg, Frede

    2012-01-01

    The enabling of ac microgrids in distribution networks allows delivering distributed power and providing grid support services during regular operation of the grid, as well as powering isolated islands in case of faults and contingencies, thus increasing the performance and reliability of the ele......The enabling of ac microgrids in distribution networks allows delivering distributed power and providing grid support services during regular operation of the grid, as well as powering isolated islands in case of faults and contingencies, thus increasing the performance and reliability...

  7. Offline detection of broken rotor bars in AC induction motors

    Science.gov (United States)

    Powers, Craig Stephen

    ABSTRACT. OFFLINE DETECTION OF BROKEN ROTOR BARS IN AC INDUCTION MOTORS. The detection of the broken rotor bar defect in medium- and large-sized AC induction machines is currently one of the most difficult tasks for the motor condition and monitoring industry. If a broken rotor bar defect goes undetected, it can cause a catastrophic failure of an expensive machine. If a broken rotor bar defect is falsely determined, it wastes time and money to physically tear down and inspect the machine only to find an incorrect diagnosis. Previous work in 2009 at Baker/SKF-USA in collaboration with the Korea University has developed a prototype instrument that has been highly successful in correctly detecting the broken rotor bar defect in ACIMs where other methods have failed. Dr. Sang Bin and his students at the Korea University have been using this prototype instrument to help the industry save money in the successful detection of the BRB defect. A review of the current state of motor conditioning and monitoring technology for detecting the broken rotor bar defect in ACIMs shows improved detection of this fault is still relevant. An analysis of previous work in the creation of this prototype instrument leads into the refactoring of the software and hardware into something more deployable, cost effective and commercially viable.

  8. Cascaded Buck-Boost AC/AC converter%级联式Buck-Boost AC/AC变换器

    Institute of Scientific and Technical Information of China (English)

    张友军; 丁明昌; 任永保; 王阿敏; 翁振明

    2010-01-01

    详细分析了Buck型和Boost型AC/AC变换器的工作原理及其控制方法,在此基础上提出了一种新型级联式Buck-Boost AC/AC变换器及其三模式控制策略.三模式控制策略是比较输入电压与基准输出电压的大小,使得变换器只有3种工作模式:Buck模式、Boost模式和滤波模式.该电路虽然由Buck型和Boost型AC/AC变换器2级变换器级联而成,并采用2级占空比调制,但实际上最多只存在一级功率变换,具有控制简单、变换效率高、开关管电压应力低等优点.仿真结果证明了级联式Buck-Boost AC/AC变换器及其控制策略的可行性和理论分析的正确性.

  9. An improved FEM model for computing transport AC loss in coils made of RABiTS YBCO coated conductors for electric machines

    DEFF Research Database (Denmark)

    Ainslie, Mark D; Rodriguez Zermeno, Victor Manuel; Hong, Zhiyong

    2011-01-01

    AC loss can be a significant problem for any applications that utilize or produce an AC current or magnetic field, such as an electric machine. The authors investigate the electromagnetic properties of high temperature superconductors with a particular focus on the AC loss in superconducting coils...... Superconductivity Group's all-superconducting permanent magnet synchronous motor design. To validate the modeling results, the transport AC loss of a stator coil is measured using an electrical method based on inductive compensation by means of a variable mutual inductance. Finally, the implications of the findings...... on the performance of the motor are discussed....

  10. Acetylated α-Tubulin Regulated by N-Acetyl-Seryl-Aspartyl-Lysyl-Proline(Ac-SDKP) Exerts the Anti-fibrotic Effect in Rat Lung Fibrosis Induced by Silica.

    Science.gov (United States)

    Xiaojun, Wang; Yan, Liu; Hong, Xu; Xianghong, Zhang; Shifeng, Li; Dingjie, Xu; Xuemin, Gao; Lijuan, Zhang; Bonan, Zhang; Zhongqiu, Wei; Ruimin, Wang; Brann, Darrell; Fang, Yang

    2016-08-31

    Silicosis is the most serious occupational disease in China. The objective of this study was to screen various proteins related to mechanisms of the pathogenesis of silicosis underlying the anti-fibrotic effect of N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) using proteomic profile analysis. We also aimed to explore a potential mechanism of acetylated α-tubulin (α-Ac-Tub) regulation by Ac-SDKP. Two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) were used to assess the different protein expression profiles between control and silicosis rats treated with or without Ac-SDKP. Twenty-nine proteins were identified to be potentially involved in the progression of silicosis and the anti-fibrotic effect of Ac-SDKP. Our current study finds that 1) the lost expression of Ac-Tub-α may be a new mechanism in rat silicosis; 2) treatment of silicotic rats with N-acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP) inhibits myofibroblast differentiation and collagen deposition accompanied by stabilizing the expression of α-Ac-Tub in vivo and in vitro, which is related with deacetylase family member 6 (HDAC6) and α-tubulin acetyl transferase (α-TAT1). Our data suggest that α-Ac-Tub regulation by Ac-SDKP may potentially be a new anti-fibrosis mechanism.

  11. Appropriate green phosphor of SrSi2O2N2:Eu2+,Mn2+ for AC LEDs.

    Science.gov (United States)

    Yeh, Chiao-Wen; Li, Ye; Wang, Jing; Liu, Ru-Shi

    2012-07-30

    An AC (alternating current) LED exhibited the advantages of a low drive current, low static electricity, lack of a need for a rectifier, and high extraction efficiency. The input operating voltage of an AC LED is around 80V, and its operating frequency is 120 Hz or less. When the voltage is converted, a time gap of 1/120 s (10 ms), called dead time, is generated. This time gap is closely related to the scintillation phenomenon. Therefore, AC LEDs that have a phosphor composition, whose half-life composition can compensate for dead time that is generated during the voltage conversion, are sought to solve the problem of scintillation. The object of this work is to provide a phosphor SrSi(2)O(2)N(2):Eu(2+),Mn(2+) for AC LEDs, in which the dead time that is generated during the voltage conversion is compensated for by the half-life of the phosphor.

  12. YBCO thin films in ac and dc films

    CERN Document Server

    Shahzada, S

    2001-01-01

    We report studies on the dc magnetization of YBCO thin films in simultaneously applied dc and ac fields. The effect of the ac fields is to decrease the irreversible magnetization drastically leading to complete collapse of the hysteresis loops for relatively small ac fields (250e). The magnitude of the decrease depends on the component of the ac field parallel to the c-axis. The decrease is non-linear with ac amplitude and is explained in the framework of the critical state response of ultra thin films in perpendicular geometry. The ac fields increase the relaxation rapidly at short times while the long time response appears unaffected. (author)

  13. Ac hopping conduction at extreme disorder takes place on the percolating cluster

    DEFF Research Database (Denmark)

    Schrøder, Thomas; Dyre, J. C.

    2008-01-01

    Simulations of the random barrier model show that ac currents at extreme disorder are carried almost entirely by the percolating cluster slightly above threshold; thus contributions from isolated low activation-energy clusters are negligible. The effective medium approximation in conjunction with...

  14. The Wechsler ACS Social Perception Subtest: A Preliminary Comparison with Other Measures of Social Cognition

    Science.gov (United States)

    Kandalaft, Michelle R.; Didehbani, Nyaz; Cullum, C. Munro; Krawczyk, Daniel C.; Allen, Tandra T.; Tamminga, Carol A.; Chapman, Sandra B.

    2012-01-01

    Relative to other cognitive areas, there are few clinical measures currently available to assess social perception. A new standardized measure, the Wechsler Advanced Clinical Solutions (ACS) Social Perception subtest, addresses some limitations of existing measures; however, little is known about this new test. The first goal of this investigation…

  15. The Wechsler ACS Social Perception Subtest: A Preliminary Comparison with Other Measures of Social Cognition

    Science.gov (United States)

    Kandalaft, Michelle R.; Didehbani, Nyaz; Cullum, C. Munro; Krawczyk, Daniel C.; Allen, Tandra T.; Tamminga, Carol A.; Chapman, Sandra B.

    2012-01-01

    Relative to other cognitive areas, there are few clinical measures currently available to assess social perception. A new standardized measure, the Wechsler Advanced Clinical Solutions (ACS) Social Perception subtest, addresses some limitations of existing measures; however, little is known about this new test. The first goal of this investigation…

  16. AC loss of the short coaxial superconducting cable model made from ReBCO coated tapes

    Energy Technology Data Exchange (ETDEWEB)

    Souc, J; Goemoery, F; Vojenciak, M; Frolek, L [Institute of Electrical Engineering., Centre of Excellence CENG, SAS, 841 04 Bratislava (Slovakia); Isfort, D; Ehrenberg, J; Bock, J [Nexans SuperConductors GmbH, Chemiepark Knapsack 50351, Huerth (Germany); Usoskin, A; Rutt, A [EHTS GmbH and Co. KG, Alzenau, (EAS, HANAU) (Germany)], E-mail: eleksouc@savba.sk

    2008-02-15

    Coaxial cable model with both the core as well as the shield conductor made from high-temperature superconducting tapes of the 2nd generation was constructed. AC current was fed to the model of 0.5 m length using a cold core transformer system. The core consists of 14 EHTS YBCO tapes of 4 mm width, and its properties have been published already. Now the system was completed by the shield conductor using 16 ReBCO tapes of 10 mm width produced by Nexans. In this contribution, the properties of the shield conductor are reported in detail. The experimental data on ac transport loss are presented and compared with ac transport loss of the superconducting core. The currents in individual tapes and the total cable current was monitored using Rogowski coils. Significant non-uniformity of the current distribution was found, which is a common issue in short cable models. Therefore, the AC transport loss of the shield conductor was measured by 16 lifted loops placed along the cable, using the averaging method to extract the true loss voltage.

  17. A Generalised Fault Protection Structure Proposed for Uni-grounded Low-Voltage AC Microgrids

    Science.gov (United States)

    Bui, Duong Minh; Chen, Shi-Lin; Lien, Keng-Yu; Jiang, Jheng-Lun

    2016-04-01

    This paper presents three main configurations of uni-grounded low-voltage AC microgrids. Transient situations of a uni-grounded low-voltage (LV) AC microgrid (MG) are simulated through various fault tests and operation transition tests between grid-connected and islanded modes. Based on transient simulation results, available fault protection methods are proposed for main and back-up protection of a uni-grounded AC microgrid. In addition, concept of a generalised fault protection structure of uni-grounded LVAC MGs is mentioned in the paper. As a result, main contributions of the paper are: (i) definition of different uni-grounded LVAC MG configurations; (ii) analysing transient responses of a uni-grounded LVAC microgrid through line-to-line faults, line-to-ground faults, three-phase faults and a microgrid operation transition test, (iii) proposing available fault protection methods for uni-grounded microgrids, such as: non-directional or directional overcurrent protection, under/over voltage protection, differential current protection, voltage-restrained overcurrent protection, and other fault protection principles not based on phase currents and voltages (e.g. total harmonic distortion detection of currents and voltages, using sequence components of current and voltage, 3I0 or 3V0 components), and (iv) developing a generalised fault protection structure with six individual protection zones to be suitable for different uni-grounded AC MG configurations.

  18. AcsA-AcsB: The core of the cellulose synthase complex from Gluconacetobacter hansenii ATCC23769.

    Science.gov (United States)

    McManus, John B; Deng, Ying; Nagachar, Nivedita; Kao, Teh-hui; Tien, Ming

    2016-01-01

    The gram-negative bacterium, Gluconacetobacter hansenii, produces cellulose of exceptionally high crystallinity in comparison to the cellulose of higher plants. This bacterial cellulose is synthesized and extruded into the extracellular medium by the cellulose synthase complex (CSC). The catalytic component of this complex is encoded by the gene AcsAB. However, several other genes are known to encode proteins critical to cellulose synthesis and are likely components of the bacterial CSC. We have purified an active heterodimer AcsA-AcsB from G. hansenii ATCC23769 to homogeneity by two different methods. With the purified protein, we have determined how it is post-translationally processed, forming the active heterodimer AcsA-AcsB. Additionally, we have performed steady-state kinetic studies on the AcsA-AcsB complex. Finally through mutagenesis studies, we have explored the roles of the postulated CSC proteins AcsC, AcsD, and CcpAx.

  19. Driving Human Motor Cortical Oscillations Leads to Behaviorally Relevant Changes in Local GABAA Inhibition: A tACS-TMS Study.

    Science.gov (United States)

    Nowak, Magdalena; Hinson, Emily; van Ede, Freek; Pogosyan, Alek; Guerra, Andrea; Quinn, Andrew; Brown, Peter; Stagg, Charlotte J

    2017-04-26

    Beta and gamma oscillations are the dominant oscillatory activity in the human motor cortex (M1). However, their physiological basis and precise functional significance remain poorly understood. Here, we used transcranial magnetic stimulation (TMS) to examine the physiological basis and behavioral relevance of driving beta and gamma oscillatory activity in the human M1 using transcranial alternating current stimulation (tACS). tACS was applied using a sham-controlled crossover design at individualized intensity for 20 min and TMS was performed at rest (before, during, and after tACS) and during movement preparation (before and after tACS). We demonstrated that driving gamma frequency oscillations using tACS led to a significant, duration-dependent decrease in local resting-state GABAA inhibition, as quantified by short interval intracortical inhibition. The magnitude of this effect was positively correlated with the magnitude of GABAA decrease during movement preparation, when gamma activity in motor circuitry is known to increase. In addition, gamma tACS-induced change in GABAA inhibition was closely related to performance in a motor learning task such that subjects who demonstrated a greater increase in GABAA inhibition also showed faster short-term learning. The findings presented here contribute to our understanding of the neurophysiological basis of motor rhythms and suggest that tACS may have similar physiological effects to endogenously driven local oscillatory activity. Moreover, the ability to modulate local interneuronal circuits by tACS in a behaviorally relevant manner provides a basis for tACS as a putative therapeutic intervention.SIGNIFICANCE STATEMENT Gamma oscillations have a vital role in motor control. Using a combined tACS-TMS approach, we demonstrate that driving gamma frequency oscillations modulates GABAA inhibition in the human motor cortex. Moreover, there is a clear relationship between the change in magnitude of GABAA inhibition induced

  20. The Impact Study of a Statcom on Commutation Failures in an HVDC Inverter Feeding a Weak AC System

    Science.gov (United States)

    Khatir, Mohamed; Zidi, Sid-Ahmed; Fellah, Mohammed-Karim; Hadjeri, Samir; Flitti, Mohamed

    2012-03-01

    The Static Synchronous Compensator (STATCOM) devices are pure power electronics devices that use voltage source, IGBT, IGCT or GTO based converters to generate reactive current. This paper illustrates the effect of STATCOM connected whit an HVDC inverter feeding a weak AC network, on the recovery from commutation failures following AC side disturbances. MATLAB/SIMULINK simulation results have demonstrated the robust performance of the proposed system based on the first CIGRÉ HVDC Benchmark model against commutation failures.

  1. Modeling of long High Voltage AC Underground

    DEFF Research Database (Denmark)

    Gudmundsdottir, Unnur Stella; Bak, Claus Leth; Wiechowski, W. T.

    2010-01-01

    This paper presents the work and findings of a PhD project focused on accurate high frequency modelling of long High Voltage AC Underground cables. The project is cooperation between Aalborg University and Energinet.dk. The objective of the project is to investigate the accuracy of most up to date...

  2. 76 FR 65633 - RIN 1904-AC43

    Science.gov (United States)

    2011-10-24

    ... 1904-AC43. Comments may be submitted using any of the following methods: Federal eRulemaking Portal... and avoid the use of special characters or any form of encryption. Postal Mail: Ms. Brenda Edwards, U... FR 56678 (September 14, 2011) to make available and invite comments on the framework document...

  3. Operating experience with factory-made air-insulated 1AC/2AC switchgear systems; Erste Betriebserfahrungen mit fabrikgefertigten, luftisolierten 1AC-/2AC-Schaltanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Northe, J. [Balfour Beatty Rail GmbH, Offenbach (Germany); Loenard, D. [Bombardier Transportation GmbH, Mannheim (Germany)

    2007-07-01

    Today, factory-made air-insulated switchgear systems of the type TracFeed {sup registered} are available for all supply versions of 16.7 Hz and 50 Hz a.c. railways. These are supported by auxiliary equipment to ensure reliable railway operation through specific protective functions and a simplified line test. (orig.)

  4. Thermal Simulation of AC Electromagnetic Contactor

    Institute of Scientific and Technical Information of China (English)

    NIUChun-ping; CHENDe-gui; ZHANGJing-shu; LIXing-wen

    2005-01-01

    Transient magnetic circuit method is adopted to calculate the power loss in winding and shading coil. Based on the analysis of heat transfer process in AC contactor, a thermal model is proposed and the temperature field distribution is simulated with 3-D FEM of ANSYS.Comparison of simulation results with measurements shows that the proposed method is effective.

  5. From Beamline to Scanner with 225Ac

    Science.gov (United States)

    Robertson, Andrew K. H.; Ramogida, Caterina F.; Kunz, Peter; Rodriguez-Rodriguez, Cristina; Schaffer, Paul; Sossi, Vesna

    2016-09-01

    Due to the high linear energy transfer and short range of alpha-radiation, targeted radiation therapy using alpha-emitting pharmaceuticals that successfully target small disease clusters will kill target cells with limited harm to healthy tissue, potentially treating the most aggressive forms of cancer. As the parent of a decay chain with four alpha- and two beta-decays, 225Ac is a promising candidate for such a treatment. However, this requires retention of the entire decay chain at the target site, preventing the creation of freely circulating alpha-emitters that reduce therapeutic effect and increase toxicity to non-target tissues. Two major challenges to 225Ac pharmaceutical development exist: insufficient global supply, and the difficulty of preventing toxicity by retaining the entire decay chain at the target site. While TRIUMF works towards large-scale (C i amounts) production of 225Ac, we already use our Isotope Separation On-Line facility to provide small (overview of this research program and the journey of 225Ac from the beamline to the scanner. This research is funded by the Natural Sciences and Engineering Research Council of Canada.

  6. A dry-cooled AC quantum voltmeter

    Science.gov (United States)

    Schubert, M.; Starkloff, M.; Peiselt, K.; Anders, S.; Knipper, R.; Lee, J.; Behr, R.; Palafox, L.; Böck, A. C.; Schaidhammer, L.; Fleischmann, P. M.; Meyer, H.-G.

    2016-10-01

    The paper describes a dry-cooled AC quantum voltmeter system operated up to kilohertz frequencies and 7 V rms. A 10 V programmable Josephson voltage standard (PJVS) array was installed on a pulse tube cooler (PTC) driven with a 4 kW air-cooled compressor. The operating margins at 70 GHz frequencies were investigated in detail and found to exceed 1 mA Shapiro step width. A key factor for the successful chip operation was the low on-chip power consumption of 65 mW in total. A thermal interface between PJVS chip and PTC cold stage was used to avoid a significant chip overheating. By installing the cryocooled PJVS array into an AC quantum voltmeter setup, several calibration measurements of dc standards and calibrator ac voltages up to 2 kHz frequencies were carried out to demonstrate the full functionality. The results are discussed and compared to systems with standard liquid helium cooling. For dc voltages, a direct comparison measurement between the dry-cooled AC quantum voltmeter and a liquid-helium based 10 V PJVS shows an agreement better than 1 part in 1010.

  7. Aging, Counterfeiting Configuration Control (AC3)

    Science.gov (United States)

    2010-01-31

    relabeled fake microcircuit chips from overseas - threaten the reliability, safety, and performance of DoD systems. These systems are vulnerable... NASA , Raytheon internal, etc. Aging, Counterfeiting Configuration Control (AC3) Page 13 of 28 are important in determining the alert’s priority

  8. Design and implementation of co-operative control strategy for hybrid AC/DC microgrids

    Science.gov (United States)

    Mahmud, Rasel

    This thesis is mainly divided in two major sections: 1) Modeling and control of AC microgrid, DC microgrid, Hybrid AC/DC microgrid using distributed co-operative control, and 2) Development of a four bus laboratory prototype of an AC microgrid system. At first, a distributed cooperative control (DCC) for a DC microgrid considering the state-of-charge (SoC) of the batteries in a typical plug-in-electric-vehicle (PEV) is developed. In DC microgrids, this methodology is developed to assist the load sharing amongst the distributed generation units (DGs), according to their ratings with improved voltage regulation. Subsequently, a DCC based control algorithm for AC microgrid is also investigated to improve the performance of AC microgrid in terms of power sharing among the DGs, voltage regulation and frequency deviation. The results validate the advantages of the proposed methodology as compared to traditional droop control of AC microgrid. The DCC-based control methodology for AC microgrid and DC microgrid are further expanded to develop a DCC-based power management algorithm for hybrid AC/DC microgrid. The developed algorithm for hybrid microgrid controls the power flow through the interfacing converter (IC) between the AC and DC microgrids. This will facilitate the power sharing between the DGs according to their power ratings. Moreover, it enables the fixed scheduled power delivery at different operating conditions, while maintaining good voltage regulation and improved frequency profile. The second section provides a detailed explanation and step-by-step design and development of an AC/DC microgrid testbed. Controllers for the three-phase inverters are designed and tested on different generation units along with their corresponding inductor-capacitor-inductor (LCL) filters to eliminate the switching frequency harmonics. Electric power distribution line models are developed to form the microgrid network topology. Voltage and current sensors are placed in the proper

  9. EFEK MEDAN LISTRIK AC TERHADAP PERTUMBUHAN BAKTERI Klebsiella Pneumoniae

    Directory of Open Access Journals (Sweden)

    Mokhamad Tirono

    2013-05-01

    Full Text Available Penghambatan pertumbuhan bakteri Klebsiella pneumoniai pada ikan kembung dengan medan listrik alternating current (AC telah dilakukan. Medan Listrik AC yang digunakan divariasi dari 0,38 kV/cm sampai 5 kV/cm dengan frekwensi 50 Hz, sedangkan waktu paparan 10 menit. Pada penelitian ini dilakukan penumbuhan bakteri Klebsiella pneumonia pada media NA selama 24 jam dan berikutnya ditumbuhkan pada medium NB dan ikan yang sudah disterilkan selama 24 jam. Bakteri yang sudah ditumbuhkan pada medium NB dan ikan kemudian dipapar dengan medan listrik AC dengan variasi kuat medan yaitu dari 0,38 kV/cm sampai 5 kV/cm dengan waktu paparan 10 menit. Sehabis dipapar bakteri ditumbuhkan pada medium NB selama 24 jam dan berikutnya diencerkan dengan aquades untuk dihitung jumlah koloninya. Hasil uji menggunkan univariate analysis of variance didapatkan nilai signifisi 0,000 yang menunjukkan ada perbedaan yang signifikan untuk masing-masing kuat medan listrik. Menggunakan statistic post hoc test diperoleh bahwa dengan kuat medan 5 kV/cm mempunyai faktor hambat 0,99, sedangkan  dengan  kuat   medan  0,38   kV/cm  mempunyai  faktor   hambat   0,3.   Terhambatnya pertumbuhan bakteri ini disebabkan oleh karena membran seluler bakteri rusak, sehingga menyebabkan keluarnya materi intraseluler. Kerusakan membran seluler disebabkan oleh terjadinya elektroporasi yang dapat meningkatkan potensial membran. Semakin tinggi medan listrik yang dikenakan, maka peningkatan tegangan transmembran semakin tinggi.

  10. Spin Backflow and ac Voltage Generation by Spin Pumping and the Inverse Spin Hall Effect

    Science.gov (United States)

    Jiao, HuJun; Bauer, Gerrit E. W.

    2013-05-01

    The spin current pumped by a precessing ferromagnet into an adjacent normal metal has a constant polarization component parallel to the precession axis and a rotating one normal to the magnetization. The former is now routinely detected as a dc voltage induced by the inverse spin Hall effect (ISHE). Here we compute ac ISHE voltages much larger than the dc signals for various material combinations and discuss optimal conditions to observe the effect. The backflow of spin is shown to be essential to distill parameters from measured ISHE voltages for both dc and ac configurations.

  11. Numerical Simulation of the Discharge Efficiency in Five-electrode AC PDP

    Institute of Scientific and Technical Information of China (English)

    何锋; 李永东; 刘纯亮; 孙鉴

    2004-01-01

    A new type of AC PDP (alternating current plasma display panel) cell with a fiveelectrode structure is developed to improve the luminous efficiency of AC PDP. The discharge efficiency of this new cell structure is investigated by a 2D fluid simulation. Continuity equations and flux density equations for charged particles and excited atoms, energy balance equation for electrons are included in the model. The discharge gas is He+5%Xe. The reactions of ionization,excitation, recombination, and radiation are taken into account. The vacuum ultraviolet radiation efficiency of the five-electrode cell structure is about 20% higher than that of a conventional three-electrode cell structure.

  12. Implementation and Control of an AC/DC/AC Converter for Double Wound Flywheel Application

    Directory of Open Access Journals (Sweden)

    J. G. Oliveira

    2012-01-01

    Full Text Available An all-electric driveline based on a double wound flywheel, connected in series between main energy storage and a wheel motor, is presented. The flywheel works as a power buffer, allowing the battery to deliver optimized power. It also separates electrically the system in two sides, with the battery connected to the low voltage side and the wheel motor connected to the high voltage side. This paper presents the implementation and control of the AC/DC/AC converter, used to connect the flywheel high voltage windings to the wheel motor. The converter general operation and the adopted control strategy are discussed. The implementation of the AC/DC/AC converter has been described from a practical perspective. Results from experimental tests performed in the full-system prototype are presented. The prototype system is running with satisfactory stability during acceleration mode. Good efficiency and unity power factor could be achieved, based on vector control and space vector modulation.

  13. AcEST Contig - AcEST | LSDB Archive [Life Science Database Archive metadata

    Lifescience Database Archive (English)

    Full Text Available [ Credits ] BLAST Search Image Search Home About Archive Update History Contact us ...contig.zip File URL: ftp://ftp.biosciencedbc.jp/archive/acest/LATEST/acestcontig....zip File size: 1.34MB Simple search URL http://togodb.biosciencedbc.jp/togodb/view/archive_acestcontig#en Da...Joomla SEF URLs by Artio About This Database Database Description Download License Update History of This Database Site Policy | Contact Us AcEST Contig - AcEST | LSDB Archive ...

  14. Dicty_cDB: FCL-AC21 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available FCL (Link to library) FCL-AC21 (Link to dictyBase) - - - Contig-U15479-1 FCL-AC21E ...(Link to Original site) - - - - - - FCL-AC21E 632 Show FCL-AC21 Library FCL (Link to library) Clone ID FCL-AC2... http://dictycdb.biol.tsukuba.ac.jp/CSM/FCL/FCL-AC/FCL-AC21Q.Seq.d/ Representative seq. ID FCL-AC2...1E (Link to Original site) Representative DNA sequence >FCL-AC21 (FCL-AC21Q) /CSM/FCL/FCL-AC/FCL-AC2...M/SL/SLG7-D/SLG773Q.Seq.d/ 1205 0.0 FCL-AC21 (FCL-AC21Q) /CSM/FCL/FCL-AC/FCL-AC21

  15. Distributed Optimal Power Flow of AC/DC Interconnected Power Grid Using Synchronous ADMM

    Science.gov (United States)

    Liang, Zijun; Lin, Shunjiang; Liu, Mingbo

    2017-05-01

    Distributed optimal power flow (OPF) is of great importance and challenge to AC/DC interconnected power grid with different dispatching centres, considering the security and privacy of information transmission. In this paper, a fully distributed algorithm for OPF problem of AC/DC interconnected power grid called synchronous ADMM is proposed, and it requires no form of central controller. The algorithm is based on the fundamental alternating direction multiplier method (ADMM), by using the average value of boundary variables of adjacent regions obtained from current iteration as the reference values of both regions for next iteration, which realizes the parallel computation among different regions. The algorithm is tested with the IEEE 11-bus AC/DC interconnected power grid, and by comparing the results with centralized algorithm, we find it nearly no differences, and its correctness and effectiveness can be validated.

  16. Low AC Loss YBCO Coated Conductor Geometry by Direct Inkjet Printing

    Energy Technology Data Exchange (ETDEWEB)

    Rupich, Martin, Dr. [American Superconductor Corporation; Duckworth, Robert, Dr. [Oak Ridge National Laboratory

    2009-10-01

    The second generation (2G) high temperature superconductors (HTS) wire offers potential benefits for many electric power applications, including ones requiring filamentized conductors with low ac loss, such as transformers and fault current limiters. However, the use of 2G wire in these applications requires the development of both novel multi-filamentary conductor designs with lower ac losses and the development of advanced manufacturing technologies that enable the low-cost manufacturing of these filamentized architectures. This Phase I SBIR project focused on testing inkjet printing as a potential low-cost, roll-to-roll manufacturing technique to fabricate potential low ac loss filamentized architectures directly on the 2G template strips.

  17. Zigzag Connected Autotransformer-Based 24-pulse AC-DC Converter

    Science.gov (United States)

    Xiao-qiang, Chen; Hao, Qiu

    2015-02-01

    In this paper, a zigzag connected autotransformer-based 24-pulse AC-DC converter is designed, modeled and simulated to feed direct torque controlled induction motor drives. Winding arrangements and parameters of the autotransformer and interphase reactor are given. Moreover, the design procedure of the autotransformer is modified to make it suitable for retrofit applications. Simulation results indicate that the system is capable of eliminating up to 21st harmonics in the ac mains current. The effect of load variation and load character is also studied to demonstrate the performance and effectiveness of the proposed 24-pulse converters. A set of power quality indices at ac mains and dc side are presented to compare the performance of 6-, 12- and 24-pulse converters.

  18. Production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

    Science.gov (United States)

    Melville, G; Meriarty, H; Metcalfe, P; Knittel, T; Allen, B J

    2007-09-01

    The increasing application of Ac-225 for cancer therapy indicates the potential need for its increased production and availability. The production of Ac-225 has been achieved using bremsstrahlung photons from an 18 MV medical linear accelerator (linac) to bombard a Ra-226 target. A linac dose of 2800 Gy produced about 64 microCi of Ra-225, which decays to Ac-225. This result, while consistent with the theoretical calculations, is far too low to be of practical use. A more powerful linac is required that runs at a higher current, longer pulse length and higher frequency for practical production. This process could also lead to the reduction of the nuclear waste product Ra-226.

  19. AC-93253 triggers the downregulation of melanoma progression markers and the inhibition of melanoma cell proliferation.

    Science.gov (United States)

    Karwaciak, Iwona; Gorzkiewicz, Michal; Ryba, Katarzyna; Dastych, Jaroslaw; Pulaski, Lukasz; Ratajewski, Marcin

    2015-07-01

    A major challenge in anti-melanoma therapy is to develop treatments that are effective for advanced melanoma patients. Unfortunately, the currently used regimens are not efficient and have unsatisfactory effects on disease progression, thus increasing the pressure to develop new, profitable drugs and to identify new molecular targets. Here, we show for the first time that AC-93253, a SIRT2 inhibitor, exerts a negative effect on the expression of a set of genes involved in the progression and chemoresistance (e.g., oncogenes, apoptosis-related genes, ABC transporter genes, and cell cycle control genes) of melanoma cells. Furthermore, melanoma cells exposed to AC-93253 and doxorubicin displayed altered biological responses, including apoptosis and proliferation, compared to cells exposed to single treatments. Taken together, we conclude that the usage of AC-93253 in combined therapy could be a promising strategy for melanoma patients.

  20. Instantaneous velocity measurement of AC electroosmotic flows by laser induced fluorescence photobleaching anemometer with high temporal resolution

    Science.gov (United States)

    Zhao, Wei; Yang, Fang; Qiao, Rui; Wang, Guiren; Rui Qiao Collaboration

    2015-11-01

    Understanding the instantaneous response of flows to applied AC electric fields may help understand some unsolved issues in induced-charge electrokinetics and enhance performance of microfluidic devices. Since currently available velocimeters have difficulty in measuring velocity fluctuations with frequency higher than 1 kHz, most experimental studies so far focus only on the average velocity measurement in AC electrokinetic flows. Here, we present measurements of AC electroosmotic flow (AC-EOF) response time in microchannels by a novel velocimeter with submicrometer spatial resolution and microsecond temporal resolution, i.e. laser-induced fluorescence photobleaching anemometer (LIFPA). Several parameters affecting the AC-EOF response time to the applied electric signal were investigated, i.e. channel length, transverse position and solution conductivity. The experimental results show that the EOF response time under a pulsed electric field decreases with the reduction of the microchannel length, distance between the detection position to the wall and the conductivity of the solution. This work could provide a new powerful tool to measure AC electrokinetics and enhance our understanding of AC electrokinetic flows.

  1. AC loss evaluation of an HTS insert for high field magnet cooled by cryocoolers

    Science.gov (United States)

    Kajikawa, Kazuhiro; Awaji, Satoshi; Watanabe, Kazuo

    2016-12-01

    AC losses in a high temperature superconducting (HTS) insert coil for 25-T cryogen-free superconducting magnet during its initial energization are numerically calculated under the assumption of slab approximation. The HTS insert consisting of 68 single pancakes wound using coated conductors generates a central magnetic field of 11.5 T in addition to the contribution of 14.0 T from a set of low temperature superconducting (LTS) outsert coils. Both the HTS insert and the LTS coils are cooled using cryocoolers, and energized simultaneously up to the central field of 25.5 T with a constant ramp rate for 60 min. The influences of the magnitudes and orientations of locally applied magnetic fields, magnetic interactions between turns and transport currents flowing in the windings are taken into account in the calculations of AC losses. The locally applied fields are separated into axial and radial components, and the individual contributions of these field components to the AC losses are simply summed up to obtain the total losses. The AC losses due to the axial fields become major in the beginning of energization, whereas the total losses monotonically increase with time after the AC losses due to the radial fields become major.

  2. Study of Power Flow Algorithm of AC/DC Distribution System including VSC-MTDC

    Directory of Open Access Journals (Sweden)

    Haifeng Liang

    2015-08-01

    Full Text Available In recent years, distributed generation and a large number of sensitive AC and DC loads have been connected to distribution networks, which introduce a series of challenges to distribution network operators (DNOs. In addition, the advantages of DC distribution networks, such as the energy conservation and emission reduction, mean that the voltage source converter based multi-terminal direct current (VSC-MTDC for AC/DC distribution systems demonstrates a great potential, hence drawing growing research interest. In this paper, considering losses of the reactor, the filter and the converter, a mathematical model of VSC-HVDC for the load flow analysis is derived. An AC/DC distribution network architecture has been built, based on which the differences in modified equations of the VSC-MTDC-based network under different control modes are analyzed. In addition, corresponding interface functions under five control modes are provided, and a back/forward iterative algorithm which is applied to power flow calculation of the AC/DC distribution system including VSC-MTDC is proposed. Finally, by calculating the power flow of the modified IEEE14 AC/DC distribution network, the efficiency and validity of the model and algorithm are evaluated. With various distributed generations connected to the network at appropriate locations, power flow results show that network losses and utilization of transmission networks are effectively reduced.

  3. The Feasibility of Applying AC Driven Low-Temperature Plasma for Multi-Cycle Detonation Initiation

    Science.gov (United States)

    Zheng, Dianfeng

    2016-11-01

    Ignition is a key system in pulse detonation engines (PDE). As advanced ignition methods, nanosecond pulse discharge low-temperature plasma ignition is used in some combustion systems, and continuous alternating current (AC) driven low-temperature plasma using dielectric barrier discharge (DBD) is used for the combustion assistant. However, continuous AC driven plasmas cannot be used for ignition in pulse detonation engines. In this paper, experimental and numerical studies of pneumatic valve PDE using an AC driven low-temperature plasma igniter were described. The pneumatic valve was jointly designed with the low-temperature plasma igniter, and the numerical simulation of the cold-state flow field in the pneumatic valve showed that a complex flow in the discharge area, along with low speed, was beneficial for successful ignition. In the experiments ethylene was used as the fuel and air as oxidizing agent, ignition by an AC driven low-temperature plasma achieved multi-cycle intermittent detonation combustion on a PDE, the working frequency of the PDE reached 15 Hz and the peak pressure of the detonation wave was approximately 2.0 MPa. The experimental verifications of the feasibility in PDE ignition expanded the application field of AC driven low-temperature plasma. supported by National Natural Science Foundation of China (No. 51176001)

  4. Stimulus presentation at specific neuronal oscillatory phases experimentally controlled with tACS: implementation and applications

    Directory of Open Access Journals (Sweden)

    Sanne Ten Oever

    2016-10-01

    Full Text Available In recent years it has become increasingly clear that both the power and phase of oscillatory brain activity can influence the processing and perception of sensory stimuli. Transcranial alternating current stimulation (tACS can phase-align and amplify endogenous brain oscillations and has often been used to control and thereby study oscillatory power. Causal investigation of oscillatory phase is more difficult, as it requires precise real-time temporal control over both oscillatory phase and sensory stimulation. Here, we present hardware and software solutions allowing temporally precise presentation of sensory stimuli during tACS at desired tACS phases, enabling causal investigations of oscillatory phase. We developed freely available and easy to use software, which can be coupled with standard commercially available hardware to allow flexible and multi-modal stimulus presentation (visual, auditory, magnetic stimuli, etc. at pre-determined tACS-phases, opening up a range of new research opportunities. We validate that stimulus presentation at tACS phase in our setup is accurate to the sub-millisecond level with high inter-trial consistency. Conventional methods investigating the role of oscillatory phase such as magneto-/electroencephalography can only provide correlational evidence. Using brain stimulation with the described methodology enables investigations of the causal role of oscillatory phase. This setup turns oscillatory phase into an independent variable, allowing innovative and systematic studies of its functional impact on perception and cognition.

  5. Electroporation of cells using EM induction of ac fields by a magnetic stimulator

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C; Robinson, M P [Department of Electronics, University of York, Heslington, York YO10 5DD (United Kingdom); Evans, J A [Academic Unit of Medical Physics, University of Leeds, Leeds LS2 9JT (United Kingdom); Smye, S W [Department of Medical Physics and Engineering, Leeds Teaching Hospitals, St. James' s University Hospital, Leeds LS9 7TF (United Kingdom); O' Toole, P [Department of Biology, University of York, Heslington, York YO10 5DD (United Kingdom)

    2010-02-21

    This paper describes a method of effectively electroporating mammalian cell membranes with pulsed alternating-current (ac) electric fields at field strengths of 30-160 kV m{sup -1}. Although many in vivo electroporation protocols entail applying square wave or monotonically decreasing pulses via needles or electrode plates, relatively few have explored the use of pulsed ac fields. Following our previous study, which established the effectiveness of ac fields for electroporating cell membranes, a primary/secondary coil system was constructed to produce sufficiently strong electric fields by electromagnetic induction. The primary coil was formed from the applicator of an established transcranial magnetic stimulation (TMS) system, while the secondary coil was a purpose-built device of a design which could eventually be implanted into tissue. The effects of field strength, pulse interval and cumulative exposure time were investigated using microscopy and flow cytometry. Results from experiments on concentrated cell suspensions showed an optimized electroporation efficiency of around 50%, demonstrating that electroporation can be practicably achieved by inducing such pulsed ac fields. This finding confirms the possibility of a wide range of in vivo applications based on magnetically coupled ac electroporation.

  6. Power Electronic Transformer based Three-Phase PWM AC Drives

    Science.gov (United States)

    Basu, Kaushik

    A Transformer is used to provide galvanic isolation and to connect systems at different voltage levels. It is one of the largest and most expensive component in most of the high voltage and high power systems. Its size is inversely proportional to the operating frequency. The central idea behind a power electronic transformer (PET) also known as solid state transformer is to reduce the size of the transformer by increasing the frequency. Power electronic converters are used to change the frequency of operation. Steady reduction in the cost of the semiconductor switches and the advent of advanced magnetic materials with very low loss density and high saturation flux density implies economic viability and feasibility of a design with high power density. Application of PET is in generation of power from renewable energy sources, especially wind and solar. Other important application include grid tied inverters, UPS e.t.c. In this thesis non-resonant, single stage, bi-directional PET is considered. The main objective of this converter is to generate adjustable speed and magnitude pulse width modulated (PWM) ac waveforms from an ac or dc grid with a high frequency ac link. The windings of a high frequency transformer contains leakage inductance. Any switching transition of the power electronic converter connecting the inductive load and the transformer requires commutation of leakage energy. Commutation by passive means results in power loss, decrease in the frequency of operation, distortion in the output voltage waveform, reduction in reliability and power density. In this work a source based partially loss-less commutation of leakage energy has been proposed. This technique also results in partial soft-switching. A series of converters with novel PWM strategies have been proposed to minimize the frequency of leakage inductance commutation. These PETs achieve most of the important features of modern PWM ac drives including 1) Input power factor correction, 2) Common

  7. Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ficko, Bradley W., E-mail: Bradley.W.Ficko@Dartmouth.edu; Nadar, Priyanka M.; Diamond, Solomon G.

    2015-02-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurements to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement set and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R{sup 2}=0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R{sup 2}=0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R{sup 2}=0.97, p<0.001). These results demonstrate the concept of ASI and advantages of sASI. - Highlights: • Development of an AC susceptibility imaging model. • Comparison of AC susceptibility imaging (ASI) and susceptibility magnitude imaging (SMI). • Demonstration of ASI and spectroscopic ASI (sASI) using three different magnetic nanoparticle types. • SASI scan separation of three different magnetic nanoparticles samples using 5 spectroscopic frequencies. • Demonstration of biological feasibility of sASI.

  8. Morphological studies of the galaxy populations in distant "Butcher-Oemler" clusters with HST. II. AC103, AC118 and AC114 at z=0.31

    CERN Document Server

    Couch, W J; Smail, I; Ellis, Richard S; Sharples, R M

    1997-01-01

    We present new results of a program to study the detailed morphologies of galaxies in intermediate redshift clusters and hence understand the physical origin of the enhanced star formation in these environments at earlier epochs. Deep, high resolution imagery has been obtained of 3 rich clusters, AC103,AC118 & AC114 at z=0.31, using the WFPC2 on HST. For AC103 & AC118, single pointings covering a central 0.5x0.5Mpc have been obtained; for AC114, 4 pointings covering a 1.2x0.7Mpc area have been obtained, allowing the more outer regions of a distant cluster to be studied. Hubble types plus evidence for dynamical interactions and/or structural abnormalities have been determined visually for all galaxies down to R=22.25 in AC103 & AC118 and R=23.0 in AC114.We find the numbers of spirals (Sa-Sdm) in our clusters to be up to 4x higher than that seen in present-day clusters; only in the virialised core of our most massive regular cluster, AC114, do we see morphological fractions approaching those of the ...

  9. Investigation of AC/DC Converters with PFC and Output Isolation Diodes

    Directory of Open Access Journals (Sweden)

    Mihail H. Antchev,

    2014-02-01

    Full Text Available This paper presents computer simulation and experimental results of a research on two parallel connected single phase AC/DC converters with power factor correction and control scheme realized by L4981A controller. The analysis is focused on: power factor and harmonic distortion of the grid current; transient process of settlement of the steady state of the output voltage and its pulsations; output currents sharing at initial start and steady state.

  10. AcMNPV As A Model for Baculovirus DNA Replication

    Institute of Scientific and Technical Information of China (English)

    Eric B. Carstens

    2009-01-01

    Baculoviruses were first identified as insect-specific pathogens, and it was this specificity that lead to their use as safe, target specific biological pesticides. For the past 30 years, AcMNPV has served as the subject of intense basic molecular research into the baculovirus infectious cycle including the interaction of the virus with a continuous insect cell line derived from Spodoptera frugiperda. The studies on baculoviruese have led to an in-depth understanding of the physical organization of the viral genomes including many complete genomic sequences, the time course of gene expression, and the application of this basic research to the use of baculoviruses not only as insecticides, but also as a universal eukaryotic protein expression system, and a potential vector in gene therapy. A great deal has also been discovered about the viral genes required for the replication of the baculovirus genome, while much remains to be learned about the mechanism of viral DNA replication. This report outlines the current knowledge of the factors involved in baculovirus DNA replication, using data on AcMNPV as a model for most members of the Baculoviridae.

  11. ACS sampling system: design, implementation, and performance evaluation

    Science.gov (United States)

    Di Marcantonio, Paolo; Cirami, Roberto; Chiozzi, Gianluca

    2004-09-01

    By means of ACS (ALMA Common Software) framework we designed and implemented a sampling system which allows sampling of every Characteristic Component Property with a specific, user-defined, sustained frequency limited only by the hardware. Collected data are sent to various clients (one or more Java plotting widgets, a dedicated GUI or a COTS application) using the ACS/CORBA Notification Channel. The data transport is optimized: samples are cached locally and sent in packets with a lower and user-defined frequency to keep network load under control. Simultaneous sampling of the Properties of different Components is also possible. Together with the design and implementation issues we present the performance of the sampling system evaluated on two different platforms: on a VME based system using VxWorks RTOS (currently adopted by ALMA) and on a PC/104+ embedded platform using Red Hat 9 Linux operating system. The PC/104+ solution offers, as an alternative, a low cost PC compatible hardware environment with free and open operating system.

  12. Research on the Plasma Anemometer Based on AC Glow Discharge

    Directory of Open Access Journals (Sweden)

    Bing Yu

    2017-01-01

    Full Text Available A new plasma anemometer based on AC glow discharge is designed in this article. Firstly, theoretical analysis of plasma anemometer working principle is introduced to prove the feasibility of the experimental measurement method. Then the experiments are carried out to study the effects of different parameters on the static discharge characteristics of the plasma anemometer system, by which the system optimization methods are obtained. Finally, several groups of appropriate parameters are selected to build the plasma anemometer system based on resistance capacitance coupling negative feedback AC glow discharge, and different airflow speeds are applied to obtain the achievable velocity measurement range. The results show that there is a linear relationship between airflow velocity and discharge current in an allowable error range, which can be applied for airflow velocity measurement. Negative feedback coupling module, which is composed of the coupling resistance and the coupling capacitance, has good effects on improving the system stability. The measurement range of the airflow velocity is significantly increased when the electrode gap is 3 mm, coupling resistance is 470 Ω, and coupling capacitance is 220 pF.

  13. Methods for Addressing Missing Data with Applications from ACS Exams

    Science.gov (United States)

    Brandriet, Alexandra; Holme, Thomas

    2015-01-01

    As part of the ACS Examinations Institute (ACS-EI) national norming process, student performance data sets are collected from professors at colleges and universities from around the United States. Because the data sets are collected on a volunteer basis, the ACS-EI often receives data sets with only students' total scores and without the students'…

  14. Importance of Attenuation Correction (AC) for Small Animal PET Imaging

    DEFF Research Database (Denmark)

    El Ali, Henrik H.; Bodholdt, Rasmus Poul; Jørgensen, Jesper Tranekjær;

    2012-01-01

    was performed. Methods: Ten NMRI nude mice with subcutaneous implantation of human breast cancer cells (MCF-7) were scanned consecutively in small animal PET and CT scanners (MicroPETTM Focus 120 and ImTek’s MicroCATTM II). CT-based AC, PET-based AC and uniform AC methods were compared. Results: The activity...

  15. General analytical solutions for DC/AC circuit network analysis

    CERN Document Server

    Rubido, Nicolás; Baptista, Murilo S

    2014-01-01

    In this work, we present novel general analytical solutions for the currents that are developed in the edges of network-like circuits when some nodes of the network act as sources/sinks of DC or AC current. We assume that Ohm's law is valid at every edge and that charge at every node is conserved (with the exception of the source/sink nodes). The resistive, capacitive, and/or inductive properties of the lines in the circuit define a complex network structure with given impedances for each edge. Our solution for the currents at each edge is derived in terms of the eigenvalues and eigenvectors of the Laplacian matrix of the network defined from the impedances. This derivation also allows us to compute the equivalent impedance between any two nodes of the circuit and relate it to currents in a closed circuit which has a single voltage generator instead of many input/output source/sink nodes. Contrary to solving Kirchhoff's equations, our derivation allows to easily calculate the redistribution of currents that o...

  16. Study on Fault Current of DFIG during Slight Fault Condition

    OpenAIRE

    Xiangping Kong; Zhe Zhang; Xianggen Yin; Zhenxing Li

    2013-01-01

    In order to ensure the safety of DFIG when severe fault happens, crowbar protection is adopted. But during slight fault condition, the crowbar protection will not trip, and the DFIG is still excited by AC-DC-AC converter. In this condition, operation characteristics of the converter have large influence on the fault current characteristics of DFIG. By theoretical analysis and digital simulation, the fault current characteristics of DFIG during slight voltage dips are studied. And the influenc...

  17. RHIC AC DIPOLE DESIGN AND CONSTRUCTION.

    Energy Technology Data Exchange (ETDEWEB)

    BAI,M.; METH,M.; PAI,C.; PARKER,B.; PEGGS,S.; ROSER,T.; SANDERS,R.; TRBOJEVIC,D.; ZALTSMAN,A.

    2001-06-18

    Two ac dipoles with vertical and horizontal magnetic field have been proposed at RHIC for applications in linear and non-linear beam dynamics and spin manipulations. A magnetic field amplitude of 380 Gm is required to produce a coherent oscillation of 5 times the rms beam size at the top energy. We take the ac dipole frequency to be 1.0% of the revolution frequency away from the betatron frequency. To achieve the strong magnetic field with minimum power loss, an air-core magnet with two seven turn winding of low loss Litz wire resonating at 64 kHz is designed. The system is also designed to allow one to connect the two magnet winding in series to resonate at 37 kHz for the spin manipulation. Measurements of a half length prototype magnet are also presented.

  18. Nanorod dynamics in ac electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Ruda, H E; Shik, A [Centre for Advanced Nanotechnology, University of Toronto, Toronto, M5S 3E3 (Canada)

    2010-06-11

    Metal and semiconductor nanorods polarized by an external electric field tend to align parallel to this field. We derived the equation of motion for this alignment, taking into account electrostatic forces, thermal fluctuations and viscous resistance of the liquid the nanorods are suspended in. It was solved for a strong ac electric field, as well as for the combination of strong dc and weak ac fields. The results were used for calculations of the capacity of the nanorod solution, its frequency dispersion and dependence on the field strength. Modification of the nanorod absorption spectra under the influence of an electric field was also considered. It was shown that metal nanorods in laser radiation, with the frequency belonging to the interval between longitudinal and transverse plasmon modes, tend to align perpendicular, rather than parallel, to the optical electric field.

  19. Toxicity and binding analyses of Bacillus thuringiensis toxin Vip3A in Cry1Ac-resistant and-susceptible strains of Helicoverpa armigera (Hübner)

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qian; CHEN Li-zhen; LU Qiong; ZHANG Yan; LIANG Ge-mei

    2015-01-01

    The Bacil us thuringiensis vegetative insecticidal protein, Vip3A, represents a new family of Bt toxin and is currently ap-plied to commercial transgenic cotton. To determine whether the Cry1Ac-resistant Helicoverpa armigera is cross-resistant to Vip3Aa protein, insecticidal activities, proteolytic activations and binding properties of Vip3Aa toxin were investigated using Cry1Ac-susceptible (96S) and Cry1Ac-resistant H. armigera strain (Cry1Ac-R). The toxicity of Vip3Aa in Cry1Ac-R slightly reduced compared with 96S, the resistance ratio was only 1.7-fold. The digestion rate of ful-length Vip3Aa by gut juice extracts from 96S was little faster than that from Cry1Ac-R. Surface plasmon resonance (SPR) showed there was no signiifcant difference between the binding afifnity of Vip3Aa and BBMVs between 96S and Cry1Ac-R strains, and there was no signiifcant competitive binding between Vip3Aa and Cry1Ac in susceptible or resistant strains. So there had little cross-resistance between Vip3Aa and Cry1Ac,Vip3A+Cry proteins maybe the suitable pyramid strategy to control H. armigera in China in the future.

  20. Effect of Low-Frequency AC Magnetic Susceptibility and Magnetic Properties of CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

    Directory of Open Access Journals (Sweden)

    Yuan-Tsung Chen

    2014-01-01

    Full Text Available In this investigation, the low-frequency alternate-current (AC magnetic susceptibility (χac and hysteresis loop of various MgO thickness in CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ determined coercivity (Hc and magnetization (Ms and correlated that with χac maxima. The multilayer films were sputtered onto glass substrates and the thickness of intermediate barrier MgO layer was varied from 6 to 15 Å. An experiment was also performed to examine the variation of the highest χac and maximum phase angle (θmax at the optimal resonance frequency (fres, at which the spin sensitivity is maximal. The results reveal that χac falls as the frequency increases due to the relationship between magnetization and thickness of the barrier layer. The maximum χac is at 10 Hz that is related to the maximal spin sensitivity and that this corresponds to a MgO layer of 11 Å. This result also suggests that the spin sensitivity is related to both highest χac and maximum phase angle. The corresponding maximum of χac is related to high exchange coupling. High coercivity and saturation magnetization contribute to high exchange-coupling χac strength.

  1. 78 FR 49318 - Availability of Draft Advisory Circular (AC) 90-106A and AC 20-167A

    Science.gov (United States)

    2013-08-13

    ... Systems (78 FR 34935-34958) (Docket No.: FAA-2013-0485; Notice No. 1209). AC 90-106A, Enhanced Flight... the Federal Register published on April 11, 2000 (65 FR 19477-19478), as well as at http://DocketsInfo... Federal Aviation Administration Availability of Draft Advisory Circular (AC) 90-106A and AC 20-...

  2. Lazy AC-Pattern Matching for Rewriting

    OpenAIRE

    Walid Belkhir; Alain Giorgetti

    2012-01-01

    We define a lazy pattern-matching mechanism modulo associativity and commutativity. The solutions of a pattern-matching problem are stored in a lazy list composed of a first substitution at the head and a non-evaluated object that encodes the remaining computations. We integrate the lazy AC-matching in a strategy language: rewriting rule and strategy application produce a lazy list of terms.

  3. Lazy AC-Pattern Matching for Rewriting

    Directory of Open Access Journals (Sweden)

    Walid Belkhir

    2012-04-01

    Full Text Available We define a lazy pattern-matching mechanism modulo associativity and commutativity. The solutions of a pattern-matching problem are stored in a lazy list composed of a first substitution at the head and a non-evaluated object that encodes the remaining computations. We integrate the lazy AC-matching in a strategy language: rewriting rule and strategy application produce a lazy list of terms.

  4. The Effect of Temperature Dependence of AC Losses in a Bi-2223/Ag Insert of an 8-T Superconducting Magnet

    DEFF Research Database (Denmark)

    Wang, Lei; Wang, Qiuliang; Wang, Hui;

    2016-01-01

    A conduction-cooled split-gap superconducting magnet system with a center field of 8 T has been designed and fabricated in the Institute of Electrical Engineering, Chinese Academy of Sciences. The system consists of two Bi-2223/Ag coils and six NbTi coils. Due to a large aspect ratio of the high...... dependence relations of the critical current density .1c are considered. The calculations are carried out in three steps. First, to estimate the magnitude of ac losses rapidly in the Bi-2223/Ag coils, the ac losses are calculated when the Bi-2223/Ag and NbTi coils are simultaneously charged, in which...... the temperature distribution is not considered. Second, the temperature variation is considered to calculate the ac losses under the same operating conditions with those in the first case. Finally, the NbTi coils are charged first, followed by the Bi-2223/Ag coils; the ac losses calculated are less than those...

  5. Draft genome sequence of Mesotoga strain PhosAC3, a mesophilic member of the bacterial order Thermotogales, isolated from a digestor treating phosphogypsum in Tunisia

    National Research Council Canada - National Science Library

    Ben Hania, Wajdi; Fadhlaoui, Khaled; Brochier-Armanet, Céline; Persillon, Cécile; Postec, Anne; Hamdi, Moktar; Dolla, Alain; Ollivier, Bernard; Fardeau, Marie-Laure; Le Mer, Jean; Erauso, Gaël

    2015-01-01

    .... This genus currently contain two described species, M. prima and M. infera. Strain PhosAc3, isolated from a Tunisian digestor treating phosphogypsum, is phylogenetically closely related to M. prima strain MesG1.Ag.4.2...

  6. Cryocooled Josephson standards for AC voltage metrology

    Science.gov (United States)

    Durandetto, P.; Sosso, A.; Monticone, E.; Trinchera, B.; Fretto, M.; Lacquaniti, V.

    2017-05-01

    The Josephson effect is worldwide used as a basis for constant reference voltages in national metrological institutes and in calibration laboratories of industry. Research on Josephson voltage standards is aiming at a fundamental change also in the metrology of the volt for AC and arbitrary waveforms: programmable Josephson voltage standards converting a digital code into a quantum-accurate stepwise waveform are already available in primary laboratories and even more advanced standards for converting sub-nanosecond binary coded pulses into any arbitrary signal with quantum accuracy are now actively developed and tested. A new experimental setup based on a two-stage Gifford-McMahon cryocooler has been developed at INRiM for the operation of AC-Josephson voltage standards. Among its distinct features, the possibility of employing both the aforementioned techniques (programmable and pulsed Josephson voltage standards) is particularly interesting. Quantum-based AC voltage sine waves have been synthesized with both programmable and pulse-driven arrays, although their accuracy is still limited by thermal oscillations due to the cryocooler piston motion.

  7. The Hubble Legacy Archive ACS Grism Data

    CERN Document Server

    Kuemmel, M; Fosbury, R; Haase, J; Hook, R N; Kuntschner, H; Lombardi, M; Micol, A; Nilsson, K K; Stoehr, F; Walsh, J R

    2011-01-01

    A public release of slitless spectra, obtained with ACS/WFC and the G800L grism, is presented. Spectra were automatically extracted in a uniform way from 153 archival fields (or "associations") distributed across the two Galactic caps, covering all observations to 2008. The ACS G800L grism provides a wavelength range of 0.55-1.00 \\mu$m, with a dispersion of $40 \\ \\AA / pixel$ and a resolution of $\\sim 80\\ \\AA$ for point-like sources. The ACS G800L images and matched direct images were reduced with an automatic pipeline that handles all steps from archive retrieval, alignment and astrometric calibration, direct image combination, catalogue generation, spectral extraction and collection of metadata. The large number of extracted spectra (73,581) demanded automatic methods for quality control and an automated classification algorithm was trained on the visual inspection of several thousand spectra. The final sample of quality controlled spectra includes 47,919 datasets (65% of the total number of extracted spect...

  8. AC susceptibilities of grain-textured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, N. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan)], E-mail: saka@te.kyusan-u.ac.jp; Fukuda, Y.; Koga, M.; Akune, T. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan); Khan, H.R. [Institut von Ionenstrahl und Vakuum Technologie, 73728 Esslingen (Germany); Lueders, K. [Freie Universitaet Berlin, Arnimallee, Fac.Physik, D-14195 Berlin (Germany)

    2008-09-15

    In-phase {chi}{sub n}' and out-phase {chi}{sub n}'' components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field B{sub dc}, an amplitude B{sub a} and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low-T{sub c} metallic superconductors, {chi}{sub 1}' shows smooth transition and {chi}{sub 1}'' does single peak. High-T{sub c} oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in {chi}{sub 1}'' and shoulders in {chi}{sub 1}' appear in AC susceptibility of Hg-1223 superconductors. Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.

  9. 单相直接AC-AC变换器的实现与分析%The Implementation and Analysis of Simple Phase Direct AC-AC Converter

    Institute of Scientific and Technical Information of China (English)

    万衡; 喻嬿; 黄道

    2002-01-01

    针对传统AC-DC-AC变换存在的缺陷,采用高频调制直接AC-AC变换技术,实现了两种不同结构的单相AC-AC直接变换器,对其特点和仿真结果进行了分析,并探讨了应用前景.

  10. Cutaneous retinal activation and neural entrainment in transcranial alternating current stimulation: A systematic review

    NARCIS (Netherlands)

    Schutter, D.J.L.G.

    2016-01-01

    Transcranial alternating current stimulation (tACS) applies exogenous oscillatory electric field potentials to entrain neural rhythms and is used to investigate brain-function relationships and its potential to enhance perceptual and cognitive performance. However, due to current spread tACS can

  11. Cutaneous retinal activation and neural entrainment in transcranial alternating current stimulation: A systematic review

    NARCIS (Netherlands)

    Schutter, D.J.L.G.

    2016-01-01

    Transcranial alternating current stimulation (tACS) applies exogenous oscillatory electric field potentials to entrain neural rhythms and is used to investigate brain-function relationships and its potential to enhance perceptual and cognitive performance. However, due to current spread tACS can cau

  12. Resistojet control and power for high frequency ac buses

    Science.gov (United States)

    Gruber, Robert P.

    1987-01-01

    Resistojets are operational on many geosynchronous communication satellites which all use dc power buses. Multipropellant resistojets were selected for the Initial Operating Capability (IOC) Space Station which will supply 208 V, 20 kHz power. This paper discusses resistojet heater temperature controllers and passive power regulation methods for ac power systems. A simple passive power regulation method suitable for use with regulated sinusoidal or square wave power was designed and tested using the Space Station multipropellant resistojet. The breadboard delivered 20 kHz power to the resistojet heater. Cold start surge current limiting, a power efficiency of 95 percent, and power regulation of better than 2 percent were demonstrated with a two component, 500 W breadboard power controller having a mass of 0.6 kg.

  13. ACS/SBC Internal Lamp P-flat Monitoring

    Science.gov (United States)

    Avila, Roberto J.; Chiaberge, Marco; Bohlin, Ralph

    2016-06-01

    We report on a Cycle 23 calibration program to monitor the status of the SBC P-flat. We find random pixel to pixel changes to be small, with only ˜2% of pixels having changed by more than 3σ. There are coherent changes that we measure to be above the poisson errors, in some regions as high as 4% peak to peak. We therefore recommend that the ACS team obtain new observations in order to create a new P-flat. We also measured the degradation of the deuterium lamp used to create internal flats. The brightness of the lamp is currently ˜65% of its initial level, the degradation being dependent on lifetime usage.

  14. Molecular biology of maize Ac/Ds elements: an overview.

    Science.gov (United States)

    Lazarow, Katina; Doll, My-Linh; Kunze, Reinhard

    2013-01-01

    Maize Activator (Ac) is one of the prototype transposable elements of the hAT transposon superfamily, members of which were identified in plants, fungi, and animals. The autonomous Ac and nonautonomous Dissociation (Ds) elements are mobilized by the single transposase protein encoded by Ac. To date Ac/Ds transposons were shown to be functional in approximately 20 plant species and have become the most widely used transposable elements for gene tagging and functional genomics approaches in plants. In this chapter we review the biology, regulation, and transposition mechanism of Ac/Ds elements in maize and heterologous plants. We discuss the parameters that are known to influence the functionality and transposition efficiency of Ac/Ds transposons and need to be considered when designing Ac transposase expression constructs and Ds elements for application in heterologous plant species.

  15. Development of a hardware-based AC microgrid for AC stability assessment

    Science.gov (United States)

    Swanson, Robert R.

    As more power electronic-based devices enable the development of high-bandwidth AC microgrids, the topic of microgrid power distribution stability has become of increased interest. Recently, researchers have proposed a relatively straightforward method to assess the stability of AC systems based upon the time-constants of sources, the net bus capacitance, and the rate limits of sources. In this research, a focus has been to develop a hardware test system to evaluate AC system stability. As a first step, a time domain model of a two converter microgrid was established in which a three phase inverter acts as a power source and an active rectifier serves as an adjustable constant power AC load. The constant power load can be utilized to create rapid power flow transients to the generating system. As a second step, the inverter and active rectifier were designed using a Smart Power Module IGBT for switching and an embedded microcontroller as a processor for algorithm implementation. The inverter and active rectifier were designed to operate simultaneously using a synchronization signal to ensure each respective local controller operates in a common reference frame. Finally, the physical system was created and initial testing performed to validate the hardware functionality as a variable amplitude and variable frequency AC system.

  16. Magneto-optical measurements on high-temperature superconductors influenced by AC-fields; Magnetooptische Untersuchungen an Hochtemperatursupraleitern unter Einfluss von Frequenzfeldern

    Energy Technology Data Exchange (ETDEWEB)

    Che' Rose, Simon

    2007-01-15

    In this work magneto-optical measurements on YBa{sub 2}Cu{sub 3}O{sub 7-x} and MgB{sub 2} thin films were done. For YBCO the influence of AC-pulses on the flux and current density of a thin film with transport current was investigated. For MgB{sub 2} the influence of AC-fields on the homogenous and dendritic flux penetration was researched. (orig.)

  17. Transport AC loss characteristics of a nine strand YBCO Roebel cable

    Science.gov (United States)

    Jiang, Zhenan; Badcock, R. A.; Long, N. J.; Staines, Mike; Thakur, K. P.; Lakshmi, L. S.; Wright, A.; Hamilton, K.; Sidorov, G. N.; Buckley, R. G.; Amemiya, Naoyuki; Caplin, A. D.

    2010-02-01

    Transport AC loss in a short length of 9/2 YBCO Roebel cable (nine 2 mm wide strands) is measured. The AC loss data are compared with those in a 5/2 YBCO Roebel cable (five 2 mm wide strands) as well as that in a single strand. All the strands composing the cables and the single strand are insulated and cut from the same stock material. The validity of the measurement method was reconfirmed by results at a range of frequencies. At a wide range of It/Ic, the normalized AC losses in the Roebel cable were around 6.2-6.7 times of those in the single strand. This is less than the nine times predicted for a tight bundle of nine conductors. The normalized transport AC losses in the 5/2 Roebel cable are much smaller than those in the 9/2 Roebel. This should be due to larger superposition of magnetic field in the 9/2 Roebel. The Ic of the 9/2 and 5/2 Roebel cables is determined by serial connection of the strands. This eliminates the effect where differing resistances in the current terminations cause uneven current sharing between strands when the strands are connected in parallel.

  18. AC Conductivity and Dielectric Relaxation Behavior of Sb2S3 Bulk Material

    Science.gov (United States)

    Abd El-Rahman, K. F.; Darwish, A. A. A.; Qashou, Saleem I.; Hanafy, T. A.

    2016-07-01

    The Sb2S3 bulk material was used for next-generation anode for lithium-ion batteries. Alternative current (AC) conductivity, dielectric properties and electric modulus of Sb2S3 have been investigated. The measurements were carried out in the frequency range from 40 Hz to 5 MHz and temperature range from 293 K to 453 K. The direct current (DC) conductivity, σ DC, shows an activated behavior and the calculated activation energy is 0.50 eV. The AC conductivity, σ AC, was found to increase with the increase of temperature and frequency. The conduction mechanism of σ AC was controlled by the correlated barrier hopping model. The behavior of the dielectric constant, ɛ', and dielectric loss index, ɛ'', reveal that the polarization process of Sb2S3 is dipolar in nature. The behavior of both ɛ' and ɛ'' reveals that bulk Sb2S3 has no ferroelectric or piezoelectric phase transition. The dielectric modulus, M, gives a simple method for evaluating the activation energy of the dielectric relaxation. The calculated activation energy from M is 0.045 eV.

  19. AC Versus DC Link Comparison Based on Power Flow Analysis of a Multimachine Power System

    Directory of Open Access Journals (Sweden)

    Mohammed Abdeljalil DJEHAF

    2014-02-01

    Full Text Available Deregulation and privatization is posing new challenges on high voltage transmission and on distributions systems as well. An increasingly liberalized market will encourage trading opportunities to be identified and developed. High voltage power electronics, such as HVDC (High Voltage Direct Current and FACTS (Flexible AC Transmission Systems provide the necessary features to avoid technical problems in heavily loaded power systems; HVDC offers most advantages: it can be used for system interconnection and for control of power flow as well. The major benefit of HVDC is its incorporated ability for fault-current blocking, which is not possible with synchronous AC links. In addition, HVDC can effectively support the surrounding AC systems in case of transient fault conditions and it serves as firewall against cascading disturbances. This paper presents a comparison between HVDC link and an HVAC link in a 29 Bus multimachine system, based on load flow analysis using Newton-Raphson method for the AC link case, and sequential method for the HVDC link case.

  20. Fully digital controlled A.C. servo engraving machine based on DEC4DA

    Science.gov (United States)

    Shu, Zhibing; Chen, Xianfeng; Zhang, Hairong; Huang, Yiqun; Yan, Caizhong

    2005-12-01

    A novel engraving machine (NUT-1A) is presented, in which fully digital controlled AC system based on DEC4DA was used to improve the machining precision and sensitivity. This engraving machine was constructed around AC servo motor with encoder, controlled by a servo motor control card - DEC4DA. As the upper unit of AC servo motor, DEC4DA was a numerical control generator, which received pulses form CPU by ISA bus, and these pulses were amplified and converted to drive AC servo actuator. This novel engraving machine can achieve a higher positioning accuracy of +/-0.01mm and positioning repetition of +/-0.005mm, and its resolution is 0.001mm/0.0001mm. Moreover, because of multi-closed loops were used in the system, the steady and transient performances are more excellent. This system ensures a much quicker current regulation in closed-loop operation, of acceleration and braking in both directions, as well as stable speed characteristics. Amplifier boards are protected against excessive current, excessive temperature and short circuiting of the motor supply cables.

  1. Final design of the Korean AC/DC converters for the ITER coil power supply system

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jong-Seok, E-mail: jsoh@nfri.re.kr [ITER Korea, National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Choi, Jungwan; Suh, Jae-Hak; Choi, Jihyun [ITER Korea, National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Lee, Lacksang; Kim, Changwoo; Park, Hyungjin; Jo, Seongman; Lee, Seungyun; Hwang, Kwangcheol; Liu, Hyoyol [Dawonsys Corp., Siheung 429-450 (Korea, Republic of); Hong, Ki-Don; Sim, Dong-Joon; Lee, Jang-Soo [Hyosung Corp., Gongdeok-Dong, Seoul 121-720 (Korea, Republic of); Lee, Eui-Jae; Kwon, Yang-Hae; Lee, Dae-Yeol; Ko, Ki-Won; Kim, Jong-Min [Mobiis Corp., Yangjae-dong, Seoul 137-888 (Korea, Republic of); Song, Inho [ITER Organization, Route de Vinon sur Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); and others

    2015-10-15

    The final design of the ITER TF, CS, CC and VS AC/DC converters has been completed to implement ITER requirements following the detailed design and refinements of the preliminary design. The number of parallel thyristors and the rating of fuses are coordinated to keep those devices within the explosion limit even under most severe fault conditions. The impedance of the converter transformer has been optimized taking into account the energization inrush current, short circuit current, reactive power consumption and the available DC voltage. To ensure system integrity, AC/DC converters are mechanically divided into transformers, AC busbars, 6-pulse bridges, DC interconnecting busbars and DC reactors, and then all subsystems are decoupled by flexible links. To provide stable real time network communication down to the converters, a one GbE link is deployed between master controllers and local controllers. IEEE 1588 is implemented to the embedded controllers for precision time synchronization. This paper describes the detailed solutions implemented in the final design for the ITER AC/DC converters with R&D results of converter prototypes.

  2. Artificial neural networks for AC losses prediction in superconducting round filaments

    Science.gov (United States)

    Leclerc, J.; Makong Hell, L.; Lorin, C.; Masson, P. J.

    2016-06-01

    An extensive and fast method to estimate superconducting AC losses within a superconducting round filament carrying an AC current and subjected to an elliptical magnetic field (both rotating and oscillating) is presented. Elliptical fields are present in rotating machine stators and being able to accurately predict AC losses in fully superconducting machines is paramount to generating realistic machine designs. The proposed method relies on an analytical scaling law (ASL) combined with two artificial neural network (ANN) estimators taking 9 input parameters representing the superconductor, external field and transport current characteristics. The ANNs are trained with data generated by finite element (FE) computations with a commercial software (FlexPDE) based on the widely accepted H-formulation. After completion, the model is validated through comparison with additional randomly chosen data points and compared for simple field configurations to other predictive models. The loss estimation discrepancy is about 3% on average compared to the FEA analysis. The main advantages of the model compared to FE simulations is the fast computation time (few milliseconds) which allows it to be used in iterated design processes of fully superconducting machines. In addition, the proposed model provides a higher level of fidelity than the scaling laws existing in literature usually only considering pure AC field.

  3. Magnetic force microscopy/current contrast imaging: A new technique for internal current probing of ICs

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, A.N.; Cole, E.I. Jr.; Dodd, B.A.; Anderson, R.E.

    1993-09-01

    This invited paper describes recently reported work on the application of magnetic force microscopy (MFM) to image currents in IC conductors [1]. A computer model for MFM imaging of IC currents and experimental results demonstrating the ability to determine current direction and magnitude with a resolution of {approximately} 1 mA dc and {approximately} 1 {mu}A ac are presented. The physics of MFM signal generation and applications to current imaging and measurement are described.

  4. Moderately nonlinear diffuse-charge dynamics under an ac voltage

    Science.gov (United States)

    Stout, Robert F.; Khair, Aditya S.

    2015-09-01

    The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of Vo/(kBT /e ) , where Vo is the amplitude of the driving voltage and kBT /e is the thermal voltage with kB as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D /λDL , where D is the ion diffusivity, λD is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O (Vo3) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in Vo. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing Vo. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

  5. The AC loss evaluation of central solenoid model coil for CFETR

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yi, E-mail: shiyi@ipp.ac.cn; Wu, Yu; Hao, QiangWang; Liu, Bo; Yang, Yilin

    2016-06-15

    Highlights: • In this study, The AC loss of CFETR CSMC is calculated. • The main AC losses type and mechanics of CFETR CSMC are introduced, where the hysteresis and coupling loss of Nb{sub 3}Sn and NbTi coil are estimated. • The low frequency eddy current loss calculation of stainless steel structural components is carried out by ANSYS with 3-D separate model. • In the case of conductor joints, a 3-D ANSYS code is also used to obtain the eddy current losses for the metal components. - Abstract: The AC loss of Central Solenoid Model Coil (CSMC) of China Fusion Engineering Test Reactor (CFETR) is calculated in order to be able to determine the allowable excitation current shape in time with respect to the available cooling capacity at liquid helium temperature. Firstly, the structure and operation parameters of CFETR CSMC are summarized including the superconductor, conductor and magnetic field distribution characteristic. Secondly, the main AC losses type and mechanics of CFETR CSMC are introduced, where the hysteresis and coupling loss of Nb{sub 3}Sn and NbTi coil are estimated using of the model data and a calculation flux density distribution in the cross-section of model coil by ANSYS 2-D model. Thirdly, the low frequency eddy current loss calculation of stainless steel structural components is carried out by ANSYS/EMAG code with 3-D separately for tension rods, plates and beams model. The interaction between several components is not considered. In the case of conductor joints, a 3-D ANSYS code is also used with current force to obtain the eddy current losses for the metal components. Lastly, the individual loss components are summed up. The significant conclusions are made which can provide the valuable guidance for safe operation of CSMC.

  6. Current Sharing Technology in Transmission Conductors of Cold Dielectric High Temperature Superconducting Cables Using Second-generation HTS Wires

    Institute of Scientific and Technical Information of China (English)

    ZHU Jiahui; BAO Xuzheng; QIU Ming

    2012-01-01

    The cold dielectric high temperature superconducting (CD HTS) cable has multilayer conductors. The non-uniform AC current distribution in these multilayer conductors will increase the AC loss and decrease the current transmission efficiency. So it is important to understand the current sharing among layers in order to fully exploit the performance of the HTS cable.

  7. Alternating current organic light emitting diodes based on polymer heterojunction

    Institute of Scientific and Technical Information of China (English)

    Yewen Jiang(蒋业文); Haishu Tan(谭海曙); Jianquan Yao(姚建铨)

    2003-01-01

    Most alternating current (ac) polymer EL (electroluminescent) devices to date are based on symmetricalstructure. Here novel alternating current EL devices with asymmetric structure are successfully fabricatedby using a hole type polymer PDDOPV [poly (2,5-bis (dodecyloxy)-phenylenevinylene)] and an electrontype polymer PPQ [poly (phenyl quinoxaline)]. We report that performance of polymer devices withheterojunction in ac operation is not so sensitive to thickness of the two polymer layers as in direct current(dc) operation. This new advantage of ac operation mode over dc means easy production and cheapfacilities in large-scale production in the near future. Different emission spectra are obtained when ourac devices operate in ac mode, forward and reverse bias. Emission spectrum at reverse bias includes twoparts: one is from PDDOPV, the other is from PPQ.

  8. IEEE 802.11ac sebagai Standar Pertama untuk Gigabit Wireless LAN

    Directory of Open Access Journals (Sweden)

    Afdhal Afdhal

    2014-04-01

    Full Text Available WLAN is a technology that currently has been used widely. This technology is considered as a data transferring media technology within the LAN/MAN. To ensure that WLAN technology can be used widely in the whole world, the IEEE has set a standard known as 802.11 to be an international standard for the WLAN technology. This standard was appeared in 1997, and has been revised and improved for several times. This improvement is done to anticipate the rapidly grown WLAN market as well as to keep this technology remains effective, efficient, and reliable at any time. At the beginning of 2014, the IEEE has set 802.11ac-2013 as a new standard for WLANs that operate below 6 GHz to achieve a data rate for up to 7 Gbps. The purpose of this article is to describe comprehensively the IEEE 802.11ac standard as a result of recent changes to the regulatory for WLAN technology which is known as the first standard issued by the IEEE for the gigabit WLANs. This article discusses the goals and objectives to be achieved by 802.11ac standard as well as the parts that have been enhanced significantly both in its PHY and MAC layers. This article will also contrast the differences between the 802.11ac standard and previous WLAN standards. Finally it will also explain the level of compatibility and interoperability of 802.11ac standards with some of previous WLAN standard.Keywords: IEEE, 802.11, 802.11ac, Gigabit WLAN

  9. 隔离式SEPIC三电平AC-AC变换器的研究%Research of Isolated SEPIC Three-level AC - AC Converter

    Institute of Scientific and Technical Information of China (English)

    周振军; 李磊

    2011-01-01

    电力电子装置已在电力系统中得到了越来越广泛的应用,代表之一就是交流调压稳压装置.但是目前的交流调压稳压器多数采用AC-DC-AC的变换方式,这种调压稳压器不仅体积大、噪音大,而且开关管的电压应力大、输出电压波形质量低.提出了一种新型的隔离式交-交变换器,它是在sepic变换器(单端初级电感转换器)的基础上引入了推挽式变压器实现电气隔离.分析了工作原理,给出了控制策略,并通过仿真论证了变换器开关管电压应力小、输出电压波形质量高等特点.%Power electronics have been more widely used in power systems. One representative of power electronics is AC voltage regulator. But the AC - DC - AC conversion type is widely used for voltage regulator now. These AC voltage regulator not only have big bulk and high noise,but also with high power switch voltage stress and low quality of output waveform. To solve these problems)an isolated three-level AC - AC direct converter was proposed. It joined the push-pull transformer to achieve electrical isolation based on sepic AC -AC converter. Its operation principle and control strategies of the converter were investigated. By modeling and simulation,the performances of the AC - AC converter were verified, such as low switch voltage stress, high quality of output waveform and so on.

  10. Current Control Strategy of Chain Circuit STATCOM

    Institute of Scientific and Technical Information of China (English)

    WANG Xuan; FU Jian; TENG Letian; SUN Lijing; ZHAO Ruibin; WU Shouyuan; DENG Zhanfeng

    2012-01-01

    In order to study the current control strategy based on the chain circuit static synchronous compensator (STATCOM) dynamic model and the design control system with good stability and tracking accuracy, this paper applies the chain circuit STATCOM small signal AC model, and proposes the following assumptions:

  11. Flexible AC transmission systems modelling and control

    CERN Document Server

    Zhang, Xiao-Ping; Pal, Bikash

    2012-01-01

    The extended and revised second edition of this successful monograph presents advanced modeling, analysis and control techniques of Flexible AC Transmission Systems (FACTS). The book covers comprehensively a range of power-system control problems: from steady-state voltage and power flow control, to voltage and reactive power control, to voltage stability control, to small signal stability control using FACTS controllers. In the six years since the first edition of the book has been published research on the FACTS has continued to flourish while renewable energy has developed into a mature and

  12. Composite Based EHV AC Overhead Transmission Lines

    DEFF Research Database (Denmark)

    Sørensen, Thomas Kjærsgaard

    Overhead lines at transmission level are the backbone of any national power grid today. New overhead line projects however are at the same time subject to ever greater public resistance due to the lines environmental impact. As full undergrounding of transmission lines at extra high voltage (EHV...... and analysed with regard to the possibilities, limitations and risks widespread application of composite materials on EHV AC overhead transmission lines may present. To form the basis for evaluation of the useability of composite materials, dierent overhead line projects aimed at reducing the environmental...

  13. Electrical Model of Balanced AC HTS Power Cable

    Science.gov (United States)

    Zuijderduin, R.; Chevtchenko, O.; Smit, J. J.; Willén, D.; Melnik, I.; Geschiere, A.

    The future electricity grid will be more sustainable and it will have more power transmission and distribution capability with more electrical power added from decentralized sources on distribution level and from wind parks and other large sources on transmission level. More interconnections and more underground transmission and distribution will be put up. Use of high temperature superconducting (HTS) power cables provides solutions to many of the future grid problems caused by these trends. In this paper we present an electrical model of a balanced 6 km-long three phase triaxial HTS power cable for the Dutch project being developed by a consortium of Alliander, Ultera™ and TUD. The cable currents in all three phases are balanced by selecting proper twist pitches and insulation thickness. The paper focuses on determining inductances, capacitances and AC losses of the balanced cable. Using the developed model, we also determine the voltage drop as function of the cable length, the neutral current and the effect of the imbalanced capacitances on the current distribution of the Dutch distribution cable. The model is validated and it can be used for accurate simulation of the electrical behaviour of triaxial HTS cables in electrical grids.

  14. Effect of Alternating Current on the Cathodic Protection and Interface Structure of X80 Steel

    Science.gov (United States)

    Wang, Huiru; Du, Cuiwei; Liu, Zhiyong; Wang, Luntao; Ding, De

    2017-01-01

    This study employs potential-monitoring techniques, cyclic voltammetry tests, alternating current (AC) voltammetry methods, and surface characterization to investigate the AC corrosion of cathodically protected X80 pipeline steel. In a non-passive neutral solution at pH 7.2, a sufficiently negative potential completely protects steel at an AC current density of 100 A/m2. In an alkaline solution at pH 9.6, more serious AC corrosion occurs at more negative cathodic protection (CP) potential, whereas without CP the steel suffers negligible corrosion. In addition, the interface capacitance increases with AC amplitude. Based on these results, the AC corrosion mechanisms that function under various conditions are analyzed and described. PMID:28773211

  15. Resonance reduction for AC drives with small capacitance in the DC link

    DEFF Research Database (Denmark)

    Máthé, Lászlo; Török, Lajos; Wang, Dong;

    2016-01-01

    Pulse Width Modulated AC drives equipped with small DC-link capacitor are becoming an attractive solution for electric drive applications with moderate requirements for shaft dynamic performance. However, when these drives are fed from a weak grid a resonance between the line side impedance and t...... from the motor current. The method has been experimentally validated and the results show excellent performance. Moreover, the proposed compensation method can be applied for any kind of load connected to a three-phase passive rectifier equipped with small capacitor....... and the DC-link capacitor appears. Due to this resonance, the THD and the partially weighted harmonic distortion of the line currents are increased, which may rise compatibility problems with the AC line harmonic standards. By using vector control the motor drive is transformed into a constant power load...

  16. Electrothermally driven flows in ac electrowetting.

    Science.gov (United States)

    García-Sánchez, Pablo; Ramos, Antonio; Mugele, Frieder

    2010-01-01

    Mixing within sessile drops can be enhanced by generating internal flow patterns using ac electrowetting. While for low ac frequencies, the flow patterns have been attributed to oscillations of the drop surface, we provide here the driving mechanism of the hitherto unexplained high-frequency flows. We show that: (1) the electric field in the liquid bulk becomes important, leading to energy dissipation due to Joule heating and a temperature increase of several degrees Celsius, and (2) the fluid flow at these frequencies is generated by electrothermal effect, i.e., gradients in temperature give rise to gradients in conductivity and permittivity, the electric field acting on these inhomogeneities induces an electrical body force that generates the flow. We solved numerically the equations for the electric, temperature and flow fields. The temperature is obtained from a convection-diffusion equation where Joule heating is introduced as a source term. From the solution of the electric field and the temperature, we compute the electrical force that acts as a body force in Stokes equations. Our numerical results agree with previous experimental observations.

  17. Djungle power. A more remote AC bus

    Energy Technology Data Exchange (ETDEWEB)

    Boehnke, Heinz W. [Technosol, Jork (Germany)

    2010-07-01

    The Dzanga-Sangha Reserve in the Central African Republic is probably one of the world's most remote protected rainforest areas, much to the benefit of the rare species of lowland gorilla, forest elephant and local pygmy population Ba'Aka. The park is co-managed by the ''WWF-World Wide Fund for Nature'' with sponsoring from the German Regenwald-Stiftung. In 2008 wwf decided to switch from the old, failing generator supply to a solar hybrid mini-grid, along with stringent measures of energy conservation and management. After a careful energy audit Technosol designed an AC-bus system with a 22 kWp PV generator which should overcome the dependency on the old generators and their fuel demands. For 15 buildings, an entirely new distribution network was installed, state of the art energy saving devices introduced and an energy metering system deviced. The installation is operating since August 2009. In such remote locations, the reliability of the AC-bus over other generator-based solutions will be demonstrated and with the support of international organisations like the wwf the practical application of solar hybrid supply becomes a landmark of sustainable energy concepts. (orig.)

  18. LEDA beam diagnostics instrumentation: Beam current measurement

    Science.gov (United States)

    Barr, D.; Day, L.; Gilpatrick, J. D.; Kasemir, K.-U.; Martinez, D.; Power, J. F.; Shurter, R.; Stettler, M.

    2000-11-01

    The Low Energy Demonstration Accelerator (LEDA) facility located at Los Alamos National Laboratory (LANL) accelerates protons to an energy of 6.7 MeV and current of 100 mA operating in either a pulsed or cw mode. Two types of current measurements are used. The first is an AC or pulsed-current measurement which uses three LANL built toroids. They are placed in the beamline in such a way as to measure important transmission parameters and act as a differential current-loss machine protection system. The second system is a DC current measurement used to measure cw beam characteristics and uses toroids from Bergoz Inc. There are two of these systems, so they can also be used for transmission measurements. The AC system uses custom processing electronics whereas the DC system uses a modified Bergoz® electronics system. Both systems feature data acquisition via a series of custom TMS320C40 Digital Signal Processing (DSP) boards. Of special interest to this paper is the operation of these systems, the calibration technique, the differential current loss measurements and fast-protection processing, current droop characteristics for the AC system, and existing system noise levels. This paper will also cover the DSP system operations and their interaction with the main accelerator control system.

  19. Magnetic irreversibility in granular superconductors: ac susceptibility study

    Energy Technology Data Exchange (ETDEWEB)

    Perez, F.; Obradors, X.; Fontcuberta, J. (ICMAB, CSIC, Bellaterra, Barcelona (Spain)); Vallet, M.; Gonzalez-Calbet, J. (Lab. Magnetismo Aplicado, RENFE-U.C. Madrid, Las Matas (Spain))

    1991-12-01

    Ac susceptibility measurements of a ceramic weak-coupled superconductor in very low ac fields (2mG, 111Hz) are reported. We present evidence for the observation of the magnetic irreversibility following a ZFC-FC thermal cycling by means of ac susceptibilty measurements. It is shown that this technique also reflect local magnetic field effects in granular superconductors, as previously suggested in microwave surface resistance and I-V characteristics. (orig.).

  20. Josephson effects in an alternating current biased transition edge sensor

    CERN Document Server

    Gottardi, Luciano; Akamatsu, Hiroki; van der Kuur, Jan; Bruijn, Marcel P; Hartog, Roland H den; Hijmering, Richard; Khosropanah, Pourya; Lambert, Colin; van der Linden, Anton J; Ridder, Marcel L; Suzuki, Toyo; Gao, Jan R

    2016-01-01

    We report the experimental evidence of the ac Josephson effect in a transition edge sensor (TES) operating in a frequency domain multiplexer and biased by ac voltage at MHz frequencies. The effect is observed by measuring the non-linear impedance of the sensor. The TES is treated as a weakly linked superconducting system and within the resistively shunted junction model framework. We provide a full theoretical explanation of the results by finding the analytic solution of the non-inertial Langevian equation of the system and calculating the non-linear response of the detector to a large ac bias current in the presence of noise.

  1. Individual differences and specificity of prefrontal gamma frequency-tACS on fluid intelligence capabilities.

    Science.gov (United States)

    Santarnecchi, E; Muller, T; Rossi, S; Sarkar, A; Polizzotto, N R; Rossi, A; Cohen Kadosh, R

    2016-02-01

    Emerging evidence suggests that transcranial alternating current stimulation (tACS) is an effective, frequency-specific modulator of endogenous brain oscillations, with the potential to alter cognitive performance. Here, we show that reduction in response latencies to solve complex logic problem indexing fluid intelligence is obtained through 40 Hz-tACS (gamma band) applied to the prefrontal cortex. This improvement in human performance depends on individual ability, with slower performers at baseline receiving greater benefits. The effect could have not being explained by regression to the mean, and showed task and frequency specificity: it was not observed for trials not involving logical reasoning, as well as with the application of low frequency 5 Hz-tACS (theta band) or non-periodic high frequency random noise stimulation (101-640 Hz). Moreover, performance in a spatial working memory task was not affected by brain stimulation, excluding possible effects on fluid intelligence enhancement through an increase in memory performance. We suggest that such high-level cognitive functions are dissociable by frequency-specific neuromodulatory effects, possibly related to entrainment of specific brain rhythms. We conclude that individual differences in cognitive abilities, due to acquired or developmental origins, could be reduced during frequency-specific tACS, a finding that should be taken into account for future individual cognitive rehabilitation studies.

  2. A novel wireless power and data transmission AC to DC converter for an implantable device.

    Science.gov (United States)

    Liu, Jhao-Yan; Tang, Kea-Tiong

    2013-01-01

    This article presents a novel AC to DC converter implemented by standard CMOS technology, applied for wireless power transmission. This circuit combines the functions of the rectifier and DC to DC converter, rather than using the rectifier to convert AC to DC and then supplying the required voltage with regulator as in the transitional method. This modification can reduce the power consumption and the area of the circuit. This circuit also transfers the loading condition back to the external circuit by the load shift keying(LSK), determining if the input power is not enough or excessive, which increases the efficiency of the total system. The AC to DC converter is fabricated with the TSMC 90nm CMOS process. The circuit area is 0.071mm(2). The circuit can produce a 1V DC voltage with maximum output current of 10mA from an AC input ranging from 1.5V to 2V, at 1MHz to 10MHz.

  3. Hierarchical Control of Parallel AC-DC Converter Interfaces for Hybrid Microgrids

    DEFF Research Database (Denmark)

    Lu, Xiaonan; Guerrero, Josep M.; Sun, Kai;

    2014-01-01

    In this paper, a hierarchical control system for parallel power electronics interfaces between ac bus and dc bus in a hybrid microgrid is presented. Both standalone and grid-connected operation modes in the dc side of the microgrid are analyzed. Concretely, a three-level hierarchical control syst...... the three control levels is developed in order to adjust the main control parameters and study the system stability. Experimental results of a 2×2.2 kW parallel ac-dc converter system have shown satisfactory realization of the designed system.......In this paper, a hierarchical control system for parallel power electronics interfaces between ac bus and dc bus in a hybrid microgrid is presented. Both standalone and grid-connected operation modes in the dc side of the microgrid are analyzed. Concretely, a three-level hierarchical control system...... is implemented. In the primary control level, the decentralized control is realized by using the droop method. Local ac current proportional-resonant controller and dc voltage proportional-integral controller are employed. When the local load is connected to the dc bus, dc droop control is applied to obtain...

  4. Contact-Free Templating of 3-D Colloidal Structures Using Spatially Nonuniform AC Electric Fields.

    Science.gov (United States)

    Raveendran, Joshua; Wood, Jeffery A; Docoslis, Aristides

    2016-09-20

    The formation of ordered and regularly shaped structures of colloidal particles with the aid of spatially nonuniform electric fields is a modern research area of great interest. This work illustrates how alternating current (AC) electrokinetic effects (dielectrophoresis, electroosmosis) can serve as contact-free templates, inside which colloidal microspheres can assemble into a variety of shapes and sizes. We show how three-dimensional colloidal structures of square, circular, and diamond shape of many tens of micrometers in size can be reproducibly formed with a single set of quadrupolar microelectrodes. Numerical simulations performed help to explain the role of AC electroosmosis and AC dielectrophoresis on the shaping of these structures as a function of applied voltage and frequency. We also demonstrate how the templating repertoire is further enhanced with the simultaneous application of a second, individually controlled AC electric field, which enables a variety of asymmetric colloidal structures to be produced using the same set of quadrupolar microelectrodes. As the preservation of shape and size of such electric-field templated structures after medium evaporation still remains a big challenge, here we also report on a novel method that permits the stabilization and isolation of these particle assemblies through medium gelation and subsequent hydrogel removal with a UV/ozone treatment.

  5. AC Versus DC Link Comparison Based on Power Flow Analysis of a Multimachine Power System

    OpenAIRE

    Mohammed Abdeljalil DJEHAF; Sid Ahmed ZIDI; Youcef DJILANI KOBIBI

    2014-01-01

    Deregulation and privatization is posing new challenges on high voltage transmission and on distributions systems as well. An increasingly liberalized market will encourage trading opportunities to be identified and developed. High voltage power electronics, such as HVDC (High Voltage Direct Current) and FACTS (Flexible AC Transmission Systems) provide the necessary features to avoid technical problems in heavily loaded power systems; HVDC offers most advantages: it can be used for system int...

  6. Vector control of three-phase AC/DC front-end converter

    Indian Academy of Sciences (India)

    J S Siva Prasad; Tushar Bhavsar; Rajesh Ghosh; G Narayanan

    2008-10-01

    A vector control scheme is presented for a three-phase AC/DC converter with bi-directional power flow capability. A design procedure for selection of control parameters is discussed. A simple algorithm for unit-vector generation is presented. Starting current transients are studied with particular emphasis on high-power applications, where the line-side inductance is low. A starting procedure is presented to limit the transients. Simulation and experimental results are also presented.

  7. A mechanism-based potent sirtuin inhibitor containing Nε-thiocarbamoyl-lysine (TuAcK)

    OpenAIRE

    2011-01-01

    In the current study, we have identified Nε-thiocarbamoyl-lysine (TuAcK) as a general sirtuin inhibitory warhead which was shown to be able to confer potent sirtuin inhibition. This inhibition was also shown to be mechanism-based in that the TuAck residue was able to be processed by a sirtuin enzyme with the formation of a stalled S-alkylamidate intermediate.

  8. Protection sequence of AC/DC converters for ITER PF MAGNET coils

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Byung Hoon; Hwang, Churl Kew; Lee, Kwang Won; Jin, Jeong Tae; Chang, Sae Sik; Oh, Jong Seok; Choi, Jung Wan; Suh, Jae Hak [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Tao, Jun; Song, In Ho [ITER Organization, Paul Lez Durance (France)

    2010-06-15

    The protection sequence of an AC/DC converter for an ITER PF coil system is developed in this study. Possible faults in the coil system are simulated and the results reflected in the design of a sequence to protect the coil and converter. The inductances of the current sharing reactors and thyristor numbers in parallel with the bridge arms are optimized with the designed protection sequence

  9. AC electric motors control advanced design techniques and applications

    CERN Document Server

    Giri, Fouad

    2013-01-01

    The complexity of AC motor control lies in the multivariable and nonlinear nature of AC machine dynamics. Recent advancements in control theory now make it possible to deal with long-standing problems in AC motors control. This text expertly draws on these developments to apply a wide range of model-based control designmethods to a variety of AC motors. Contributions from over thirty top researchers explain how modern control design methods can be used to achieve tight speed regulation, optimal energetic efficiency, and operation reliability and safety, by considering online state var

  10. Autonomous Operation of Hybrid Microgrid With AC and DC Subgrids

    DEFF Research Database (Denmark)

    Chiang Loh, Poh; Li, Ding; Kang Chai, Yi

    2013-01-01

    This paper investigates on power-sharing issues of an autonomous hybrid microgrid. Unlike existing microgrids which are purely ac, the hybrid microgrid studied here comprises dc and ac subgrids interconnected by power electronic interfaces. The main challenge here is to manage power flows among all...... sources distributed throughout the two types of subgrids, which is certainly tougher than previous efforts developed for only ac or dc microgrid. This wider scope of control has not yet been investigated, and would certainly rely on the coordinated operation of dc sources, ac sources, and interlinking...

  11. AC Own Motion Percentage of Randomly Sampled Cases

    Data.gov (United States)

    Social Security Administration — Longitudinal report detailing the numbers and percentages of Appeals Council (AC) own motion review actions taken on un-appealed favorable hearing level decisions...

  12. Finite-element simulations of field and current distributions in multifilamentary superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Lucarelli, Andrea [Laboratorium fuer Festkoerperphysik, ETH-Zuerich, CH-8093 Zuerich (Switzerland); Grilli, Francesco [Ecole Polytechnique Montreal, Montreal (Canada); Luepke, Gunter [Department of Applied Science, The College of William and Mary, Williamsburg, VA 23187-8795 (United States); Haugan, Timothy J; Barnes, Paul N [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433-7919 (United States)

    2009-10-15

    We present a finite-element model for computing current and field distributions in multifilamentary superconducting thin films subjected to simultaneous effects of a transport ac current and a perpendicularly applied dc field. The model is implemented in the finite-element software package COMSOL Multiphysics and this solves Maxwell equations using a highly nonlinear resistivity to describe electrical superconducting characteristics. The time-dependent magnetic flux, current distributions, and ac losses are studied for different distances between filaments. We find that increasing the interfilamentary distance affects the transport and screening current distributions, reducing both the magnetic coupling and ac losses.

  13. DC superconducting fault current limiter

    Science.gov (United States)

    Tixador, P.; Villard, C.; Cointe, Y.

    2006-03-01

    There is a lack of satisfying solutions for fault currents using conventional technologies, especially in DC networks, where a superconducting fault current limiter could play a very important part. DC networks bring a lot of advantages when compared to traditional AC ones, in particular within the context of the liberalization of the electric market. Under normal operation in a DC network, the losses in the superconducting element are nearly zero and only a small, i.e. a low cost, refrigeration system is then required. The absence of zero crossing of a DC fault current favourably accelerates the normal zone propagation. The very high current slope at the time of the short circuit in a DC grid is another favourable parameter. The material used for the experiments is YBCO deposited on Al2O3 as well as YBCO coated conductors. The DC limitation experiments are compared to AC ones at different frequencies (50-2000 Hz). Careful attention is paid to the quench homogenization, which is one of the key issues for an SC FCL. The University of Geneva has proposed constrictions. We have investigated an operating temperature higher than 77 K. As for YBCO bulk, an operation closer to the critical temperature brings a highly improved homogeneity in the electric field development. The material can then absorb large energies without degradation. We present tests at various temperatures. These promising results are to be confirmed over long lengths.

  14. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2012-01-01

    In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.

  15. Calorimetric apparatus for alternating current loss measurements on high-temperature superconductors

    Science.gov (United States)

    Magnusson, N.; Hörnfeldt, S.

    1998-09-01

    The use of high-temperature superconductors in electric power components requires the knowledge of their alternating current (ac) losses. Methods are therefore needed to characterize the conductors with respect to their ac losses under applicationlike conditions. In this article we describe a calorimetric setup for ac loss measurements on long length high-temperature superconductors carrying ac transport currents in ac external magnetic fields at variable temperatures. The variable temperature is achieved by a thermal connection between the sample and a cooling machine. Current in copper coils generates the magnetic field parallel to the plane of the tape and perpendicular to the transport current. This current can be induced in the coil-formed sample. Two slightly different methods are used to determine the ac losses, one in which the temperature rise of the sample, caused by the ac losses, is compared to the temperature rise caused by a reference heater and another in which the increase in power dissipation of the sample is compensated for by a reduction of the power dissipation in the heater. Typical results of the ac loss measurements are presented.

  16. Statistical Distributions of Partial Discharges in Oil-paper Insulation Under AC-DC Combined Voltages

    Institute of Scientific and Technical Information of China (English)

    LI Jian; JIANG Tianyan; HE Zhiman; CHENG Changkui; BAO Lianwei

    2012-01-01

    The converter transformer is one of the most critical equipments in high-voltage direct current transmission systems.Valve-side windings have to withstand complex stresses combined of AC,DC,and pulsed voltages.Partial discharges(PDs) can thus easily occur in oil-impregnated paper insulation.The current paper presents the statistical phase-resolved distributions of partial discharges in oil-paper insulation under combined AC and DC voltage stress.First,the voltages in the converter transformer were analyzed.In the experiments,four artificial insulation defect models were designed to generate PD signals under AC-DC combined voltage stress detected by a Rogowski coil sensor.Histograms including the φ-q-n data of these PD signals were created.The variations of φ-q-n data generated by PDs in different insulation defect models were analyzed while increasing the test voltage.Experimental results showed that the PD phase-resolved distributions of different insulation defect models were different from one another.The findings of the current study are useful in further research on the mechanism and pattern recognition of PDs in converter transformers.

  17. [Intestinal occlusion and abdominal compartment syndrome (ACS)].

    Science.gov (United States)

    Stagnitti, Franco

    2009-01-01

    Intestinal occlusion is defined as an independent predictive factor of intra-abdominal hypertension (IAH) which represents an independent predictor of mortality. Baggot in 1951 classified patients operated with intestinal occlusion as being at risk for IAH ("abdominal blow-out"), recommending them for open abdomen surgery proposed by Ogilvie. Abdominal surgery provokes IAH in 44.7% of cases with mortality which, in emergency, triples with respect to elective surgery (21.9% vs 6.8%). In particular, IAH is present in 61.2% of ileus and bowel distension and is responsible for 52% of mortality (54.8% in cases with intra-abdominal infection). These patients present with an increasing intra-abdominal pressure (IAP) which, over 20-25 mmHg, triggers an Abdominal Compartment Syndrome (ACS) with altered functions in some organs arriving at Multiple Organ Dysfunction Syndrome (MODS). The intestine normally covers 58% of abdominal volume but when there is ileus distension, intestinal pneumatosis develops (third space) which can occupy up to 90% of the entire cavity. At this moment, Gastro Intestinal Failure (GIF) can appear, which is a specific independent risk factor of mortality, motor of "Organ Failure". The pathophysiological evolution has many factors in 45% of cases: intestinal pneumatosis is associated with mucosal and serous edema, capillary leakage with an increase in extra-cellular volume and peritoneal fluid collections (fourth space). The successive loss of the mucous barrier permits a bacterial translocation which includes bacteria, toxins, pro-inflammatory factors and oxygen free radicals facilitating the passage from an intra-abdominal to inter-systemic vicious cyrcle. IAH provokes the raising of the diaphragm, and vascular and visceral compressions which induce hypertension in the various spaces with compartmental characteristics. These trigger hypertension in the renal, hepatic, pelvic, thoracic, cardiac, intracranial, orbital and lower extremity areas, giving

  18. A Non-linear Controller for Single-Phase AC-AC Power Converter to meet UPS Performance Index

    Directory of Open Access Journals (Sweden)

    Abdelhafid Ait Elmahjoub

    2012-07-01

    Full Text Available This article focuses on AC-AC power converter that can be used for uninterruptible power supply (UPS. The converter is built on two stages: a AC-DC input stage and a DC-AC output stage. The two blocks are connected by an intermediate DC bus. The aim of control is threefold: i power factor correction ii regulation of DC bus iii generating a sinusoidal voltage at the output. The synthesis of controllers has been achieved through the technique of nonlinear backstepping control. A detailed analysis of the stability control system is presented. The performances of regulators have been validated by numerical simulation in MATLAB / SIMULINK.

  19. 基于Buck交-交斩波器的无功补偿器拓扑与控制方法设计%Topology and Control Strategy Design for Buck AC-AC Chopper Based Var Compensators

    Institute of Scientific and Technical Information of China (English)

    武伟; 谢少军; 汤雨; 许津铭

    2013-01-01

    首先介绍了一种新的交流斩波型无功补偿器,无需直流储能环节,系统可靠性得到加强.以Buck型交流斩波无功补偿器为对象,分析了交流斩波无功补偿的基本原理和补偿特性,推导出占空比与补偿电流之间的关系,建立了系统分析模型.在此基础上,提出了基于广义积分的直接电流控制策略,并给出了参数设计准则,最后进行了仿真和实验验证.仿真和实验结果表明,基于直接电流控制的Buck型交流斩波无功补偿器可以实现对网侧无功功率的实时补偿.%A new AC-AC chopper based var compensator is proposed. It does not require the DC-link energy storage and can effectively enhance the system reliability. The basic principles and compensation characteristics of the Buck AC/AC chopper based var compensator are described, the relationship between duty ratio and compensation current is derived, and the system analysis model is developed. A new direct current control method based on the second order generalized integral is proposed for the var compensator with detailed design criteria as well. The experimental and simulation results demonstrate that the realtime compensation of reactive power in grid side can be realized by this var compensator based on a direct current controlled Buck AC/AC chopper.

  20. AC Dielectrophoresis Using Elliptic Electrode Geometry

    Directory of Open Access Journals (Sweden)

    S. M. Rezaul Hasan

    2011-01-01

    Full Text Available This paper presents negative AC dielectrophoretic investigations using elliptic electrode geometry. Simulations of the electric field gradient variation using various ratios of the semimajor and the semiminor axis were carried out to determine the optimum elliptic geometry for the dielectrophoretic electrokinetics of specimen in an assay with laminar (low Reynolds number fluid flow. Experimental setup of the elliptic electrode assembly using PCB fabrication and electrokinetic accumulation of specimen in a dielectrophoretic cage is also being reported. Using an actuating signal between 1 kHz and 1 MHz, successful trapping of 45 μm polystyrene beads suspended in distilled water was demonstrated due to negative dielectrophoresis near 100 kHz using the novel elliptic electrode.

  1. Effective ac response in weakly nonlinear composites

    Energy Technology Data Exchange (ETDEWEB)

    Wei Enbo [Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China); Yang Zidong [College of Power Engineering, University of Shanghai Science and Technology, Shanghai 200093 (China); Gu Guoqing [Information College of Science and Technology, East China Normal University, Shanghai 200062 (China)

    2004-01-07

    The perturbation method is developed to deal with the problem of determining the effective nonlinear conductivity of Kerr-like nonlinear media under an external ac electric field. As an example, we have considered the cylindrical inclusion embedded in a host under the sinusoidal external field E{sub 1} sin (<{omega}t) + E{sub 3} sin (3<{omega}t) with frequencies{omega} and 3{omega}. The potentials of composites at higher harmonics are derived in both local inclusion particle and host regions. The effective responses of bulk nonlinear composites at basic frequency and harmonics are given for cylindrical composites in the dilute limit. Moreover, the relationships between the nonlinear effective responses at the basic frequency and the third harmonics are derived.

  2. ac impedance of the carbon monofluoride electrode

    Science.gov (United States)

    Suchanski, M. R.

    1985-09-01

    The ac impedance of carbon monofluoride (CF) half-cells and Li/CF batteries that contain 1M LiBF4/4-butyrolactone electrolyte was measured as a function of state of charge. The nonfaradaic components of the CF half-cell impedance were resolved with the aid of a one-dimensional macroscopic treatment of a porous electrode. The values of the nonfaradaic components and their variation with charge withdrawn provide information concerning the nature of cathode discharge products, the degree of tortuosity in the cathode and separator matrices, and the cathode failure mechanism. The CF electrode capacitance, as measured by the low frequency quadrature impedance, can serve as a semiquantitative measure of battery state of charge under certain conditions.

  3. The AC and DC Conductivity of Nanocomposites

    Directory of Open Access Journals (Sweden)

    David S. McLachlan

    2007-01-01

    Full Text Available The microstructures of binary (conductor-insulator composites, containing nanoparticles, will usually have one of two basic structures. The first is the matrix structure where the nanoparticles (granules are embedded in and always coated by the matrix material and there are no particle-particle contacts. The AC and DC conductivity of this microstructure is usually described by the Maxwell-Wagner/Hashin-Shtrikman or Bricklayer model. The second is a percolation structure, which can be thought to be made up by randomly packing the two types of granules (not necessarily the same size together. In percolation systems, there exits a critical volume fraction below which the electrical properties are dominated by the insulating component and above which the conducting component dominates. Such percolation systems are best analyzed using the two-exponent phenomenological percolation equation (TEPPE. This paper discusses all of the above and addresses the problem of how to distinguish among the microstructures using electrical measurements.

  4. Control of VSC-HVDC in offshore AC islands with wind power plants: Comparison of two alternatives

    DEFF Research Database (Denmark)

    Zeni, Lorenzo; Hesselbæk, Bo; Sørensen, Poul Ejnar;

    2015-01-01

    The subject of this paper is the control of offshore AC collection and export networks behind a voltage source converter based high voltage direct current transmission system. The inertia-less nature of such grids makes the control of voltages and power flows potentially more flexible, but at the...

  5. Switching from high-dose clopidogrel to prasugrel in ACS patients undergoing PCI: a single-center experience

    NARCIS (Netherlands)

    Luca, G. De; Verdoia, M.; Schaffer, A.; Suryapranata, H.; Parodi, G.; Antoniucci, D.; Marino, P.

    2014-01-01

    Prasugrel has been shown to be superior to clopidogrel in the setting of ACS patients undergoing coronary angioplasty. However, few data have been reported so far on those patients who switch from clopidogrel to prasugrel after coronary angioplasty. Aim of the current study was to evaluate the safet

  6. Severe mental illness and mortality of hospitalized ACS patients in the VHA

    Directory of Open Access Journals (Sweden)

    Shore James H

    2007-09-01

    Full Text Available Abstract Background Severe mental illness (SMI has been associated with more medical co-morbidity and less cardiovascular procedure use for older patients with myocardial infarction. However, it is unknown whether SMI is associated with increased long term mortality risk among patients presenting with acute coronary syndromes (ACS. We tested the hypothesis that SMI is associated with higher one-year mortality following ACS hospitalization. Methods All ACS patients (n = 14,194 presenting to Veterans Health Administration (VHA hospitals between October 2003 and September 2005 were included. Survival analysis evaluated the association between SMI and one-year all-cause mortality, adjusting for demographics, co-morbidities, in-hospital treatment, and discharge medications. Results Overall, 18.4 % of ACS patients had SMI. Patients with SMI were more likely female, younger, Caucasian race, have a history of alcohol abuse, liver disease, dementia, hypertension and more likely to be a current smoker; however, prior cardiac history was similar between the 2 groups. There were no significant differences in cardiac procedure use, including coronary angiogram (38.7% vs. 40.3%, p = 0.14 or coronary revascularization (31.0% vs. 32.3%, p = 0.19, and discharge medications between those with and without SMI. One-year mortality was lower for patients with SMI (15.8% vs. 19.1%, p Conclusion Among ACS patients in the VHA, SMI is prevalent, affecting almost 1 in 5 patients. However, patients with SMI were as likely to undergo coronary revascularization and be prescribed evidence-based medications at hospital discharge, and were not at elevated risk of adverse 1-year outcomes compared to patients without SMI.

  7. Severe mental illness and mortality of hospitalized ACS patients in the VHA

    Science.gov (United States)

    Plomondon, Mary E; Ho, P Michael; Wang, Li; Greiner, Gwendolyn T; Shore, James H; Sakai, Joseph T; Fihn, Stephan D; Rumsfeld, John S

    2007-01-01

    Background Severe mental illness (SMI) has been associated with more medical co-morbidity and less cardiovascular procedure use for older patients with myocardial infarction. However, it is unknown whether SMI is associated with increased long term mortality risk among patients presenting with acute coronary syndromes (ACS). We tested the hypothesis that SMI is associated with higher one-year mortality following ACS hospitalization. Methods All ACS patients (n = 14,194) presenting to Veterans Health Administration (VHA) hospitals between October 2003 and September 2005 were included. Survival analysis evaluated the association between SMI and one-year all-cause mortality, adjusting for demographics, co-morbidities, in-hospital treatment, and discharge medications. Results Overall, 18.4 % of ACS patients had SMI. Patients with SMI were more likely female, younger, Caucasian race, have a history of alcohol abuse, liver disease, dementia, hypertension and more likely to be a current smoker; however, prior cardiac history was similar between the 2 groups. There were no significant differences in cardiac procedure use, including coronary angiogram (38.7% vs. 40.3%, p = 0.14) or coronary revascularization (31.0% vs. 32.3%, p = 0.19), and discharge medications between those with and without SMI. One-year mortality was lower for patients with SMI (15.8% vs. 19.1%, p < 0.001). However, in multivariable analysis, there were no significant differences in mortality (HR 0.91; 95% CI 0.81–1.02) between patients with and without SMI. Conclusion Among ACS patients in the VHA, SMI is prevalent, affecting almost 1 in 5 patients. However, patients with SMI were as likely to undergo coronary revascularization and be prescribed evidence-based medications at hospital discharge, and were not at elevated risk of adverse 1-year outcomes compared to patients without SMI. PMID:17877804

  8. Sensorless Vector Control of AC Induction Motor Using Sliding-Mode Observer

    Directory of Open Access Journals (Sweden)

    Phuc Thinh Doan

    2013-06-01

    Full Text Available This paper develops a sensorless vector controlled method for AC induction motor using sliding-mode observer. For developing the control algorithm, modeling of AC induction motor is presented. After that, a sliding mode observer is proposed to estimate the motor speed, the rotor flux, the angular position of the rotor flux and the motor torque from monitored stator voltages and currents. The use of the nonlinear sliding mode observer provides very good performance for both low and high speed motor operation. Furthermore, the proposed system is robust in motor losses and load variations. The convergence of the proposed observer is obtained using the Lyapunov theory. Hardware and software for simulation and experiment of the AC induction motor drive are introduced. The hardware consists of a 1.5kw AC induction motor connected in series with a torque sensor and a powder brake. A controller is developed based on DSP TMS320F28355. The simulation and experimental results illustrate that fast torque and speed response with small torque ripples can be achieved. The proposed control scheme is suitable to the application fields that require high performance of torque response such as electric vehicles. doi:http://dx.doi.org/10.12777/ijse.4.2.2013.39-43 [How to cite this article: Doan, P. T., Nguyen, T. T., Jeong, S. K., Oh, S. J., & Kim, S. B. (2013. Sensorless Vector Control of AC Induction Motor Using Sliding-Mode Observer. INTERNATIONAL JOURNAL OF SCIENCE AND ENGINEERING, 4(2, 39-43; doi: http://dx.doi.org/10.12777/ijse.4.2.2013.39-43

  9. Mono-switch AC-DC/DC-DC converter for single-phase UPS%单相UPS的单开关AC-DC/DC-DC变换电路

    Institute of Scientific and Technical Information of China (English)

    李宋; 叶满园; 袁义生

    2011-01-01

    A mono-switch AC-DC/DC-DC converter used in single-phase UPS system is introduced,which consists of one power switch and six diodes. As both AC-DC rectifier and DC-DC booster,its operating modes and working principle are detailed. The single-cycle nonlinear control is adopted,which applies two low-speed PI regulators to control the voltage of two capacitors on DC link and a high-speed PI regulator to control the input current. Simulative results prove that,being simple and reliable,it outputs stable DC bus voltage with high input power factor and low THD.%介绍了一种应用在单相UPS系统中的新型单开关AC-DC/DC-DC变换电路,该电路由1个功率开关器件和6个二极管组成,能够实现AC/DC整流和DC/DC升压2种功能.在详细分析了该电路运行模式及工作原理的基础上,采用了单周期非线性控制理论对其进行控制,利于2个低速PI调节器对直流母线上的2个电容器电压进行控制,1个高速PI调节器对输入电流进行控制.仿真结果表明,该电路简单可靠,输入功率因数高,电流谐波失真小,可以获得稳定的正负直流母线电压.

  10. Equivalent circuit models for ac impedance data analysis

    Science.gov (United States)

    Danford, M. D.

    1990-01-01

    A least-squares fitting routine has been developed for the analysis of ac impedance data. It has been determined that the checking of the derived equations for a particular circuit with a commercially available electronics circuit program is essential. As a result of the investigation described, three equivalent circuit models were selected for use in the analysis of ac impedance data.

  11. A remark on Kov\\'acs' vanishing theorem

    CERN Document Server

    Fujino, Osamu

    2012-01-01

    We give an alternative proof of Kov\\'acs' vanishing theorem. Our proof is based on the standard arguments of the minimal model theory. We do not need the notion of Du Bois pairs. We reduce Kov\\'acs' vanishing theorem to the well-known relative Kawamata--Viehweg--Nadel vanishing theorem.

  12. 40 CFR Appendixes A-C to Part 403 - [Reserved

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 28 2010-07-01 2010-07-01 true A Appendixes A-C to Part 403 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GENERAL PRE-TREAT-MENT REGULATIONS FOR EXIST-ING AND NEW SOURCES OF POLLUTION Appendixes A-C to Part 403 ...

  13. Considerations for an Ac Dipole for the LHC

    CERN Document Server

    Bai, M; Fischer, W; Oddo, P; Schmickler, Hermann; Serrano, J; Jansson, A; Syphers, M; Kopp, S; Miyamoto, R

    2007-01-01

    Following successful experience at the BNL AGS, FNAL Tevatron, and CERN SPS, an AC Dipole will be adopted at the LHC for rapid measurements of ring optics. This paper describes some of the parameters of the AC dipole for the LHC, scaling from performance of the FNAL and BNL devices.

  14. Precursors of Short GRBs Registered by SPI-ACS/INTEGRAL

    Science.gov (United States)

    Minaev, P.; Pozanenko, A.

    2016-10-01

    We have searched for precursors in light curves of short gamma-ray bursts registered by SPI-ACS/INTEGRAL in 2002-2014. The portion of short bursts with precursor activity will be less than 0.4% from all short bursts registered by SPI-ACS.

  15. Scaling and universality of ac conduction in disordered solids

    DEFF Research Database (Denmark)

    Schrøder, Thomas; Dyre, Jeppe

    2000-01-01

    Recent scaling results for the ac conductivity of ionic glasses by Roling et al. [Phys. Rev. Lett. 78, 2160 (1997)] and Sidebottom [Phys. Rev. Lett. 82, 3653 (1999)] are discussed. We prove that Sidebottom's version of scaling is completely general. A new approximation to the universal ac...

  16. The topological AC effect on noncommutative phase space

    CERN Document Server

    Li, K; Li, Kang; Wang, Jianhua

    2006-01-01

    The Aharonov-Casher (AC) effect in non-commutative(NC) quantum mechanics is studied. Instead of using the star product method, we use a generalization of Bopp's shift method. After solving the Dirac equations both on noncommutative space and noncommutative phase space by the new method, we obtain the corrections to AC phase on NC space and NC phase space respectively.

  17. Power quality issues current harmonics

    CERN Document Server

    Mikkili, Suresh

    2015-01-01

    Power Quality Issues: Current Harmonics provides solutions for the mitigation of power quality problems related to harmonics. Focusing on active power filters (APFs) due to their excellent harmonic and reactive power compensation in two-wire (single phase), three-wire (three-phase without neutral), and four-wire (three-phase with neutral) AC power networks with nonlinear loads, the text:Introduces the APF technology, describing various APF configurations and offering guidelines for the selection of APFs for specific application considerationsCompares shunt active filter (SHAF) control strategi

  18. New switching pattern for AC/AC converters with RB-IGBTs for offshore wind parks

    OpenAIRE

    Mogstad, Anne Berit

    2008-01-01

    Offshore wind power has an increasing interest in the research community and among the politicians. Therefore it is important to find the right solutions to meet the environmental and commercial requirements to give offshore wind power a promising future. This thesis are proposing a new converter topology for offshore wind parks. Since the topology is based on DC transmission in stead of AC transmission it is better suited for use in this type of parks. All the converters are located in the w...

  19. Development of Low AC Loss TFA-MOD Coated Conductors

    Science.gov (United States)

    Katayama, K.; Machi, T.; Nakamura, T.; Takagi, Y.; Nakaoka, K.; Yoshizumi, M.; Izumi, T.; Shiohara, Y.

    TFA-MOD process is expected to be promising for future applications since it can produce high performance YBCO coated conductors (CCs) with low cost. Applying YBCO CCs to the power electric devices such as transformers and power cables, the reduction of alternating current (AC) loss for long wire is necessary. Multi-filamentation process, which is one of the most effective approaches for AC loss reduction, has been developed by the scribing process. We have developed the filamentation process using chemical etching. MOD derived CCs are, however, easily damaged in the chemical etching process due to existence of pores in a YBCO layer, resulting in critical current (Ic)-degradation and weak delamination strength. Consequently, it is difficult to scribe MOD derived CCs into 1mm-wide filaments for long length using the chemical etching process. Accordingly, we have studied a scribing process using an excimer laser without chemical etching. We defined P' value in this study as a function of irradiated laser power [J] divided by processing speed[m/s]. We studied relationship between the P' value and the results of scribing. It was found that we could scribe the C.C. with a sufficient depth in the condition of large P' value. Furthermore, we found that the Ic was degraded with further increase of the P' value. A 5 mm wide short sample was divided into 10 filaments by the excimer laser scribing process at the P' of 9[J/(m/s)]. The sample revealed reduction of the hysteresis loss down to 1/10 which could be expected from a theoretical prediction using the numbers of the filaments. Ic-degradation was suppressed as 28%, which was smaller than that of the scribed sample using chemical etching (Ic degradation was 38%). Subsequently, we applied the technique to a 100m long YBCO CC. The hysteresis loss of the 100m long MOD derived CC was reduced down to 1/10 (1/the number of filaments) after the multi-filamentation.

  20. Quantitative study of electrophoretic and electroosmotic enhancement during alternating current iontophoresis across synthetic membranes.

    Science.gov (United States)

    Yan, Guang; Li, S Kevin; Peck, Kendall D; Zhu, Honggang; Higuchi, William I

    2004-12-01

    One of the primary safety and tolerability limitations of direct current iontophoresis is the potential for electrochemical burns associated with the necessary current densities and/or application times required for effective treatment. Alternating current (AC) transdermal iontophoresis has the potential to eliminate electrochemical burns that are frequently observed during direct current transdermal iontophoresis. Although it has been demonstrated that the intrinsic permeability of skin can be increased by applying low-to-moderate AC voltages, transdermal transport phenomena and enhancement under AC conditions have not been systematically studied and are not well understood. The aim of the present work was to study the fundamental transport mechanisms of square-wave AC iontophoresis using a synthetic membrane system. The model synthetic membrane used was a composite Nuclepore membrane. AC frequencies ranging from 20 to 1000 Hz and AC fields ranging from 0.25 to 0.5 V/membrane were investigated. A charged permeant, tetraethyl ammonium, and a neutral permeant, arabinose, were used. The transport studies showed that flux was enhanced by increasing the AC voltage and decreasing AC frequency. Two theoretical transport models were developed: one is a homogeneous membrane model; the other is a heterogeneous membrane model. Experimental transport data were compared with computer simulations based on these models. Excellent agreement between model predictions and experimental data was observed when the data were compared with the simulations from the heterogeneous membrane model.